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1
McAlister, Harold A. "Overview of Multiple–Aperture Interferometry Binary Star Results from the Northern Hemisphere." Proceedings of the International Astronomical Union 2, S240 (August 2006): 35–44. http://dx.doi.org/10.1017/s1743921307003778.
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AbstractLong-baseline optical interferometry (LBI) can nearly close the gap in selection space between astrometric and spectroscopic detection of binary star systems, bringing the complementary powers of astrometry and spectroscopy to bear on a complete dynamical understanding of such systems, particularly including the determination of the masses of the individual stellar components. In the case of double-lined spectroscopic systems, their resolution by long-baseline interferometry also yields the orbital parallax and hence the luminosities of the individual stars. In some of these cases, the angular diameters of one or more components are accessible, and so a complete specification of a star in terms of its mass, radius and luminosity is made.The northern hemisphere is now equipped with several interferometers of unprecedented capability in terms of their baseline sizes, numbers of telescopes and telescope apertures. These instruments, most notably the Palomar Testbed Interferometer at Mt. Palomar Observatory, have produced very significant results of a number of interesting systems fulfilling interferometry's promise to produce fundamental astrophysical data at levels of accuracy that challenge or confirm astrophysical theory.This paper presents basic principles of long-baseline interferometric study of binary stars and summarizes results from northern interferometers with specific examples of their broad impact on binary star astronomy.
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Defrère, D., P. Hinz, B. Mennesson, R. Millan-Gabet, A. Skemer, V. Bailey, and T. J. Rodigas. "Searching for Faint Exozodiacal Disks: Keck Results and LBTI Status." Proceedings of the International Astronomical Union 8, S299 (June 2013): 332–33. http://dx.doi.org/10.1017/s1743921313008818.
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AbstractThe possible presence of dust in the habitable zone around nearby main-sequence stars is considered as a major hurdle toward the direct imaging of Earth-like extrasolar planets with future dedicated space-based telescopes (e.g., Roberge et al. 2012). In this context, NASA has funded two ground-based mid-infrared nulling interferometers to combine the large apertures available at the Keck Observatory and the Large Binocular Telescope (LBT). In this poster, we present the preliminary results of the extended survey carried out with the Keck Interferometer Nuller (KIN) between 2008 and 2011 and describe the forthcoming LBTI survey.
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Guinan, Edward F., Scott Engle, and Edward J. Devinney. "Advances in Telescope and Detector Technologies – Impacts on the Study and Understanding of Binary Star and Exoplanet Systems." Proceedings of the International Astronomical Union 7, S282 (July 2011): 11–20. http://dx.doi.org/10.1017/s1743921311026792.
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AbstractCurrent and planned telescope systems (both on the ground and in space) as well as new technologies will be discussed with emphasis on their impact on the studies of binary star and exoplanet systems. Although no telescopes or space missions are primarily designed to study binary stars (what a pity!), several are available (or will be shortly) to study exoplanet systems. Nonetheless those telescopes and instruments can also be powerful tools for studying binary and variable stars. For example, early microlensing missions (mid-1990s) such as EROS, MACHO and OGLE were initially designed for probing dark matter in the halos of galaxies but, serendipitously, these programs turned out to be a bonanza for the studies of eclipsing binaries and variable stars in the Magellanic Clouds and in the Galactic Bulge. A more recent example of this kind of serendipity is the Kepler Mission. Although Kepler was designed to discover exoplanet transits (and so far has been very successful, returning many planetary candidates), Kepler is turning out to be a “stealth” stellar astrophysics mission returning fundamentally important and new information on eclipsing binaries, variable stars and, in particular, providing a treasure trove of data of all types of pulsating stars suitable for detailed Asteroseismology studies. With this in mind, current and planned telescopes and networks, new instruments and techniques (including interferometers) are discussed that can play important roles in our understanding of both binary star and exoplanet systems. Recent advances in detectors (e.g. laser frequency comb spectrographs), telescope networks (both small and large – e.g. Super-WASP, HAT-net, RoboNet, Las Combres Observatory Global Telescope (LCOGT) Network), wide field (panoramic) telescope systems (e.g. Large Synoptic Survey Telescope (LSST) and Pan-Starrs), huge telescopes (e.g. the Thirty Meter Telescope (TMT), the Overwhelming Large Telescope (OWL) and the Extremely Large Telescope (ELT)), and space missions, such as the James Webb Space Telescope (JWST), the possible NASA Explorer Transiting Exoplanet Survey Satellite (TESS – recently approved for further study) and Gaia (due for launch during 2013) will all be discussed. Also highlighted are advances in interferometers (both on the ground and from space) and imaging now possible at sub-millimeter wavelengths from the Extremely Long Array (ELVA) and Atacama Large Millimeter Array (ALMA). High precision Doppler spectroscopy, for example with HARPS, HIRES and more recently the Carnegie Planet Finder Spectrograph, are currently returning RVs typically better than ~2-m/s for some brighter exoplanet systems. But soon it should be possible to measure Doppler shifts as small as ~10-cm/s – sufficiently sensitive for detecting Earth-size planets. Also briefly discussed is the impact these instruments will have on the study of eclipsing binaries, along with future possibilities of utilizing methods from the emerging field of Astroinformatics, including: the Virtual Observatory (VO) and the possibilities of analyzing these huge datasets using Neural Network (NN) and Artificial Intelligence (AI) technologies.
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Horch, Elliott P., Samuel A. Weiss, Paul M. Klaucke, Richard A. Pellegrino, and Justin D. Rupert. "Observations with the Southern Connecticut Stellar Interferometer. I. Instrument Description and First Results." Astronomical Journal 163, no. 2 (January 26, 2022): 92. http://dx.doi.org/10.3847/1538-3881/ac43bb.
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Abstract We discuss the design, construction, and operation of a new intensity interferometer, based on the campus of Southern Connecticut State University in New Haven, Connecticut. While this paper will focus on observations taken with an original two-telescope configuration, the current instrumentation consists of three portable 0.6 m Dobsonian telescopes with single-photon avalanche diode detectors located at the Newtonian focus of each telescope. Photons detected at each station are time stamped and read out with timing correlators that can give cross-correlations in timing to a precision of 48 ps. We detail our observations to date with the system, which has now been successfully used at our university in 16 nights of observing. Components of the instrument were also deployed on one occasion at Lowell Observatory, where the Perkins and Hall telescopes were made to function as an intensity interferometer. We characterize the performance of the instrument in detail. In total, the observations indicate the detection of a correlation peak at the level of 6.76σ when observing unresolved stars, and consistency with partial or no detection when observing at a baseline sufficient to resolve the star. Using these measurements, we conclude that the angular diameter of Arcturus is larger than 15 mas and that of Vega is between 0.8 and 17 mas. While the uncertainties are large at this point, both results are consistent with measures from amplitude-based long baseline optical interferometers.
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Gies, D. R. "O and B-star surface mapping." Symposium - International Astronomical Union 176 (1996): 121–28. http://dx.doi.org/10.1017/s0074180900083157.
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The massive O and B-type stars will be among the first targets of the new generation of long baseline optical interferometers (such as the CHARA Array, a 400-m diameter distributed array of five 1-m telescopes). Many of these objects are binary stars for which joint astrometric and spectroscopic observations will provide masses and distances (e.g., 15 Mon; Gies et al. 1993), but there is also great interest in resolving disks of single stars. Early interferometric observations have already resolved the flattened circumstellar disks around some Be stars (Quirrenbach et al. 1994).
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Serabyn, Eugene. "Observing Faint Companions Close to Bright Stars." Proceedings of the International Astronomical Union 7, S282 (July 2011): 163–66. http://dx.doi.org/10.1017/s1743921311027268.
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AbstractProgress in a number of technical areas is enabling imaging and interferometric observations at both smaller angular separations from bright stars and at deeper relative contrast levels. Here we discuss recent progress in several ongoing projects at the Jet Propulsion Laboratory. First, extreme adaptive optics wavefront correction has recently enabled the use of very short (i.e., blue) wavelengths to resolve close binaries. Second, phase-based coronagraphy has recently allowed observations of faint companions to within nearly one diffraction beam width of bright stars. Finally, rotating interferometers that can observe inside the diffraction beam of single aperture telescopes are being developed to detect close-in companions and bright exozodiacal dust. This paper presents a very brief summary of the techniques involved, along with some illustrative results.
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Zuckerman, B. "Radio and Millimeter Observations of Circumstellar Envelopes." Symposium - International Astronomical Union 120 (1987): 345–55. http://dx.doi.org/10.1017/s0074180900154300.
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Circumstellar chemistry has been confined largely to analysis of a few dozen molecules in the envelope of one carbon-rich star, IRC+10216. A new generation of large millimeter wavelength telescopes promises to broaden the data base to include many other stars and additional molecules. Carbon-monoxide emission has already been detected from approximately 130 stars and many of these are prime candidates for chemical studies. The detection of HCN emission in a few oxygen-rich stars was quite unexpected and indicates that nonequilibrium chemical processes are important in at least some circumstellar envelopes. New millimeter wavelength interferometers can measure the spatial distribution of various molecules for comparison with predictions of models for photodissociation, freeze-out on grains, self-shielding, and nonspherical outflow.
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Pietraszewski, K. A. R. B., C. R. Bell, J. Ring, N. K. Reay, and M. Leeper. "Multiplexed interferometric stellar oscillation spectrometry - MISOS." Symposium - International Astronomical Union 123 (1988): 517–20. http://dx.doi.org/10.1017/s0074180900158620.
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Interferometric spectrometry techniques for measuring stellar oscillations have been developed at Imperial College, resulting in two separate interferometers, the Michelson and the Fabry-Perot based instruments. They have both been used on large telescopes; the Michelson instrument to search for oscillations in solar-type stars and the Fabry-Perot instrument to measure oscillations in δScuti-type stars. So far there has been only marginal evidence for solar-type oscillations, including our observations of εCyg with ~1ms−1 precision. In order to increase the significance of future observations we are currently improving both instruments and aim to achieve a ten-fold increase in precision, i.e. ~10cms−1, by using up to 100 separate spectral lines simultaneously. Such an improvement will allow us to continue the search for solar-type oscillations.
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Davis, John. "Combining High Angular Resolution Interferometry and Spectroscopy in Studies of Stars and Stellar Systems." International Astronomical Union Colloquium 170 (1999): 390–400. http://dx.doi.org/10.1017/s025292110004882x.
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AbstractA number of long baseline optical/infrared interferometers have commenced their scientific programs or are under development. These instruments will provide accurate measurements of the angular sizes of single stars and the angular separations of binary systems at resolutions impossible with conventional telescopes. The combination of interferometric data with the results of high-resolution spectroscopy will, for many classes of objects, provide a powerful method for studying them that neither technique can do alone. Examples include the combination of interferometric and spectroscopic data for spectroscopic binaries and, in particular, for double-lined binaries, and single-lined binaries of known parallax, to determine fundamental stellar quantities. Another example concerns the study of Cepheid variables, where the combination of the data can provide an independent calibration of the zero point of the luminosity scale. The requirements and potential of these combined interferometric-spectroscopic studies are discussed.
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Anthonioz, Fabien, F. Ménard, C. Pinte, W.-F. Thi, J. B. Lebouquin, J. P. Berger, M. Benisty, et al. "The VLTi/PIONIER survey of southern TTauri disks." Proceedings of the International Astronomical Union 8, S299 (June 2013): 94–98. http://dx.doi.org/10.1017/s1743921313007990.
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AbstractStudying the inner regions of protoplanetary disks (1-10 AU) is of importance to understand the formation of planets and the accretion process feeding the forming central star. Herbig AeBe stars are bright enough to be routinely observed by Near IR interferometers. The data for the fainter T Tauri stars is much more sparse. In this contribution we present the results of our ongoing survey at the VLTI. We used the PIONIER combiner that allows the simultaneous use of 4 telescopes, yielding 6 baselines and 3 independent closure phases at once. PIONIER's integrated optics technology makes it a sensitive instrument. We have observed 22 T Tauri stars so far, the largest survey for T Tauri stars to this date.Our results demonstrate the very significant contribution of an extended component to the interferometric signal. The extended component is different from source to source and the data, with several baselines, offer a way to improve our knowledge of the disk geometry and/or composition. These results validate an earlier study by Pinte et al. 2008 and show that the dust inner radii of T Tauri disks now appear to be in better agreement with the expected position of the dust sublimation radius, contrary to previous claims.
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Boskri, Abdelkarim, Romain G. Petrov, Thami El Halkouj, Massinissa Hadjara, James Leftley, Zouhair Benkhaldoun, Pierre Cruzalèbes, Aziz Ziad, and Marcel Carbillet. "Potential and sky coverage for off-axis fringe tracking in optical long baseline interferometry." Monthly Notices of the Royal Astronomical Society 506, no. 1 (May 26, 2021): 1364–88. http://dx.doi.org/10.1093/mnras/stab1505.
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ABSTRACT The spectacular results provided by the second-generationVLTI instruments GRAVITY and MATISSE on active galactic nuclei (AGN) trigger and justify a strong increase in the sensitivity limit of optical interferometers. A key component of such an upgrade is off-axis fringe tracking. To evaluate its potential and limitations, we describe and analyse its error budget including fringe sensing precision and temporal, angular and chromatic perturbations of the piston. The global tracking error is computed using standard seeing parameters for different sites, seeing conditions and telescope sizes for the current GRAVITY Fringe Tracker (GFT) and a new concept of Hierarchical Fringe Tracker. Then, it is combined with a large catalogue of guide star candidates from Gaia to produce sky coverage maps that give the probability to find a usable off-axis guide star in any part of the observable sky. These maps can be used to set the specifications of the system, check its sensitivity to seeing conditions, and evaluate the feasibility of science programs. We check the availability of guide stars and the tracking accuracy for a large set of 15 799 Quasars to confirm the feasibility of a large program on Broad Line Regions in the K band with the GFT and show how it can be extended to the L, M, and N bands. Another set of 331 well-characterized nearby AGNs shows the high potential of MATISSE for imaging and characterization of the dust torus in the N band under off-axis tracking on both Unit Telescopes and Auxiliary Telescopes.
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Dravins, Dainis. "Observing, Modeling, and Understanding Stellar Granulation." Symposium - International Astronomical Union 138 (1990): 397–415. http://dx.doi.org/10.1017/s0074180900044405.
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Numerical simulations of the three-dimensional structure and time evolution of stellar surface convection are now possible, at least for solar-type stars. Using the output from such simulations as sets of spatially and temporally varying model atmospheres, synthetic granulation images and spectral line profiles are computed, and compared to observations. Thus obtained disk-integrated data agree with observed lineshapes and bisector patterns in different stars, and also permit stellar rotation to be determined. Such simulations represent the first generation of models that are free from the classical ad hoc parameters of ‘mixing-length’, ‘micro-’ or ‘macro-turbulence’, parameters which in the past have characterized and limited stellar astrophysics.To infer the surface structure also in more exotic stars, simpler and parametrized models must still be used to interpret observed line asymmetries. Such models suggest that rapidly rising ‘granules’ cover only a small surface fraction on early-type stars, a situation opposite to that in solar-type ones, and one likely to affect magnetic fields and stellar activity. Theoretical challenges for the future include detailed modeling also of early-type, giant, and other non-solar type stars of different rotational velocities; the hydrodynamics of entire stellar envelopes (including the interaction with global oscillations); and the interaction with magnetic fields (including their generation). Greatly increased computing power will be needed for such detailed modeling throughout the Herzsprung-Russell diagram, possibly requiring custom-designed computers.Signatures of stellar granulation are primarily observed as asymmetries and wavelength shifts in photospheric absorption lines. Observational challenges include achieving sufficient spectral resolution to fully resolve such asymmetries; identifying granulation signatures throughout the HR-diagram (including the blended spectra of cool stars); observing how line asymmetries for a given spectral type depend on stellar rotational velocity, measuring wavelength shifts between groups of different lines in the same star, and between different stars; monitoring lineshift variations during stellar activity cycles; and ultimately high-resolution spectroscopy of spatially resolved granulation structures across stellar disks. The latter will require active optics on future very large telescopes, or the use of long-baseline optical interferometers.
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Stee, Ph, D. Bonneau, F. Morand, D. Mourard, and F. Vakili. "Current studies and future prospects in stellar-structure imaging with the GI2T." Symposium - International Astronomical Union 176 (1996): 191–98. http://dx.doi.org/10.1017/s0074180900083224.
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The capability of optical long baseline interferometry for measuring the angular diameter of stars or binary separation is now well established. However, for the imaging of photospheric disk structures one needs very long baseline interferometers operated in the multi-telescope phase-closure technique. In this paper we will stress the capability of spectro-interferometric measurements to constrain the physics of hot stars. We will report our study of the interacting binary, β Lyrae, and the mass-losing Be star γ Cassiopeiae. We will look at the interpretation of both the modulus and phase data recorded by the long baseline interferometer GI2T in the southern France. The performances and limitations of spectro-interferometric techniques will also be discussed through some of the most exciting prospects within the reach of current interferometers.
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Sakamoto, K. "Kinematics and dynamics of molecular gas in galactic centers." Proceedings of the International Astronomical Union 9, S303 (October 2013): 159–67. http://dx.doi.org/10.1017/s1743921314000453.
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AbstractThe central molecular zone (CMZ) in the central half kpc of the Milky Way is a massive concentration of molecular gas in the center of a barred spiral galaxy. Current and past activities in the Galactic center include the formation of massive stars/clusters, AGN feeding, and feedback. At the same time, observations of molecular gas in external galaxies show that many disk galaxies have similar condensations of molecular gas in their central kpc or so. They also have CMZs, or nuclear molecular rings or concentrations in more common terms among extragalactic observers. The formation of the CMZs are often, but not always, related to stellar bars. The centers of nearby galaxies can provide valuable information on the general properties of galactic centers and CMZs through comparative studies of multiple galactic centers of different characteristics from various viewing angles. Linear resolutions achieved toward nearby extragalactic CMZs with modern radio interferometers are now comparable to those achieved toward the Galactic CMZ with small single-dish telescopes. I review and present work on the formation mechanism and properties of the CMZs in external galaxies with some comparisons with the CMZ of our Galaxy.
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Stee, Ph, A. Meilland, and O. L. Creevey. "Interferometry of massive stars: the next step." Proceedings of the International Astronomical Union 9, S307 (June 2014): 480–89. http://dx.doi.org/10.1017/s174392131400742x.
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AbstractWe present some new and interesting results on the complementarity between asteroseismology and interferometry, the detection of non-radial pulsations in massive stars and the possibility for evidencing differential rotation on the surface of Bn stars. We also discuss the curretn interferometric facilities, namely the Very Large Telescope Interferometer (VLTI)/AMBER, VLTI/MIDI, VLTI/PIONIER within the European Southern Observatory (ESO) context and the Center for High Angular Resolution Astronomy (CHARA) array with their current limitations. The forthcoming second-generation VLTI instruments GRAVITY and MATISSE are presented as well as the FRIEND prototype in the visible spectral domain and an update of the Navy Precision Optical Interferometer (NPOI). A conclusion is presented with a special emphasis on the foreseen difficulties for a third generation of interferometric instruments within the (budget limited) Extremely Large Telescope framework and the need for strong science cases to push a future visible beam combiner.
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Cruzalèbes, P., R. G. Petrov, S. Robbe-Dubois, J. Varga, L. Burtscher, F. Allouche, P. Berio, et al. "A catalogue of stellar diameters and fluxes for mid-infrared interferometry★." Monthly Notices of the Royal Astronomical Society 490, no. 3 (October 7, 2019): 3158–76. http://dx.doi.org/10.1093/mnras/stz2803.
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Abstract We present the Mid-infrared stellar Diameters and Fluxes compilation Catalogue (MDFC) dedicated to long-baseline interferometry at mid-infrared wavelengths (3–13 $\mu$m). It gathers data for half a million stars, i.e. nearly all the stars of the Hipparcos-Tycho catalogue whose spectral type is reported in the SIMBAD data base. We cross-match 26 data bases to provide basic information, binarity elements, angular diameter, magnitude and flux in the near and mid-infrared, as well as flags that allow us to identify the potential calibrators. The catalogue covers the entire sky with 465 857 stars, mainly dwarfs and giants from B to M spectral types closer than 18 kpc. The smallest reported values reach 0.16 $\mu$Jy in L and 0.1 $\mu$Jy in N for the flux, and 2 microarcsec for the angular diameter. We build four lists of calibrator candidates for the L and Nbands suitable with the Very Large Telescope Interferometer (VLTI) sub- and main arrays using the MATISSE instrument. We identify 1621 candidates for L and 44 candidates for N with the Auxiliary Telescopes (ATs), 375 candidates for both bands with the ATs, and 259 candidates for both bands with the Unit Telescopes (UTs). Predominantly cool giants, these sources are small and bright enough to belong to the primary lists of calibrator candidates. In the near future, we plan to measure their angular diameter with 1 per cent accuracy.
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Reasenberg, Robert D. "Microarcsecond Astrometric Interferometry." Symposium - International Astronomical Union 109 (1986): 321–30. http://dx.doi.org/10.1017/s0074180900076749.
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A small astrometric optical interferometer, Mini-POINTS, which would fit fully assembled in about one-third of the Shuttle bay, could measure the angle between stars about 90° apart. For 10th magnitude stars, an observation time of about 20 minutes would yield a measurement uncertainty of 5 microarcseconds. When compared to an astrometric telescope of comparable size which observes the same target for the same period of time, such an interferometer would achieve a greater accuracy by two to three orders of magnitude. Five design criteria lead to an instrument that achieves high precision by employing photon statistics for fringe splitting and achieves high accuracy by means of continuous internal metrology with laser interferometers. The high throughput of Mini-POINTS permits a mission design that addresses a wide variety of scientific questions.
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Horch, E., W. F. Van Altena, T. M. Girard, C. E. López, and O. Franz. "Speckle Interferometry of Double Stars from the Southern Hemisphere." Symposium - International Astronomical Union 166 (1995): 392. http://dx.doi.org/10.1017/s0074180900228684.
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We have started a new program of double star observations in the southern hemisphere which utilizes the technique of speckle interferometry. Observations are made using the Stanford University speckle interferometer on the 76-cm reflector at the Cesco Observatory at El Leoncito, Argentina (jointly run by Universidad Nacional de San Juan and Yale Southern Observatory), although we will also have access to larger aperture telescopes. The Stanford system, formerly used at Lick Observatory, is on long term loan to us from Dr. Gethyn Timothy and features a multi-anode microchannel array (MAMA) detector as the imaging device. This new program of double star research will help alleviate the continuing problem of fewer speckle observations in the southern hemisphere. In combination with other data such as the eyepiece interferometer measures of Finsen and Hipparcos parallaxes, it should also eventually contribute to a better understanding of the lower portion of the main sequence mass-luminosity relation.
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McAlister, H. A. "The Potential of Long–Baseline Optical Interferometry of Binary Stars." International Astronomical Union Colloquium 135 (1992): 527–35. http://dx.doi.org/10.1017/s0252921100007053.
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AbstractInterferometric arrays possessing sub-milliarcsecond resolution are either about to be fully scientifically productive, as in the case of the Sydney University Stellar Interferometer, or are under various stages of planning and development. The 1990’s will thus witness a hundred–fold gain in resolution over speckle interferometry at the largest telescopes and 5,000 times the resolution of classical direct imaging. Where speckle interferometry can now resolve binary stars with periods of 1 to 2 years, interferometric arrays with baselines of hundreds of meters will resolve binaries with periods of a few hours. Arrays will resolve the majority of the known spectroscopic binaries, providing a substantial increase in the quantity and quality of stellar mass determinations. Surveys for new binaries among the field stars and other restricted samples will be accomplished with unprecedented completeness. The remarkable enhancement in resolution we are about to witness from facilities like SUSI and our own proposed CHARA Array will quite literally revolutionize the field of double and multiple star research.
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Petrov, Romain G., and Stephane Lagarde. "Differential Speckle Interferometry Applied to Double Stars." International Astronomical Union Colloquium 135 (1992): 477–85. http://dx.doi.org/10.1017/s0252921100006990.
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AbstractDifferential Interferometry (DI) is the application of high angular resolution interferometric techniques to objects observed simultaneously at different wavelengths. When applied to unresolved double stars it makes it possible to measure the variation of the object photocenter with wavelength, which yields angular and spectral information well beyond the classical resolution limits. Signal–to–noise ratio analysis shows that, if DI experiments are limited by photon and speckle noise, the technique can be applied to a large number of double systems for the measurement of vectorial angular separations and of radial-velocity differences. With 4-m telescopes, there are a few tens of binary systems for which DI should permit the resolution and the measurement of the position angle of the rotation axis of at least one of the components. A preliminary experiment permitted a high SNR resolution of the double star Capella with a 1.52-m telescope and showed the current limitations of DI performances resulting from an imperfect correction of detector geometrical distortions.
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Docobo, J. A., V. S. Tamazian, M. Andrade, J. F. Ling, Y. Y. Balega, J. F. Lahulla, A. Maximov, and J. R. González–Romay. "Double Star Speckle Interferometry with the 3.5-m Telescope at Calar Alto (Almería, Spain)." Proceedings of the International Astronomical Union 2, S240 (August 2006): 490–95. http://dx.doi.org/10.1017/s1743921307006096.
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AbstractThe first results of speckle interferometry carried out with the 3.5-m telescope of the C.A.H.A. (Almería, Spain) during a run in July, 2005 are presented. Forty nine stars with separations between 0″058 and 2″1 were observed under good seeing conditions. On the basis of these observations three improved orbits are presented. The Time Allocation Committee's report with a high scientific qualification to our proposal is included. It confirms the relevance of binary and multiple star research in modern astronomy and the great significance of large telescopes in this kind of studies as well.
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Chatterjee, Shami. "Astrometric observations of neutron stars." Proceedings of the International Astronomical Union 8, S289 (August 2012): 82. http://dx.doi.org/10.1017/s1743921312021151.
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AbstractAstrometric observations of neutron stars have been conducted with a variety of techniques and over a wide range of wavelengths, ranging from radio-pulse timing and Very Long Baseline Interferometry to optical and X-ray imaging. Here I review the techniques and scientific goals behind recent high-precision neutron-star astrometry. Such measurements can yield model-independent distances and velocities that can be exploited, for example, to locate neutron-star birth sites, establish reference-frame ties, model the Galactic electron-density distribution, and constrain the astrophysics of supernova explosions. Recently, the Fermi gamma-ray space telescope has identified several highly luminous recycled pulsars, and precise measurement of their distances is of paramount importance to understand their energetics and astrophysics. The ongoing science returns from precision astrometry will continue in the long term with improvements in technology such as focal-plane arrays and synergies with new telescopes such as Gaia and the Square Kilometer Array.
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Armstrong, J. T. "Stellar Masses from Double Star Observations with the Mark III Interferometer." International Astronomical Union Colloquium 135 (1992): 492–501. http://dx.doi.org/10.1017/s0252921100007016.
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AbstractBy improving on the angular resolution possible with conventional telescopes, speckle interferometry has been adding to the list of known masses, resolving binaries with separations of 30 mas. Interferometry with separate apertures offers the possibility of going to much higher resolution.The Mark III Optical Interferometer on Mt. Wilson has been used for astrometry, for stellar diameter measurements, and for binary observations since routine operations began in late 1988. The fringe visibilty calibration uncertainty is ~1% for m < 4m at λ800 nm with good seeing, so that both binary components can be detected when the magnitude difference is 3.5m to 4m.From Mark III data, masses of eight stars have been determined. The most precise determination is for the components of the ϕ Cygni system: 2.545 ± 0.085 and 2.445 ± 0.081 M⊙. To improve on this measurement, more precise spectroscopic data are needed, as is the case for most of the systems for which we have orbits or preliminary orbits.The NRL/USNO Optical Interferometer Project is currently designing two more capable instruments: a four–element system for astrometric observations, and a six–element system for imaging. The ultimate 430-m maximum baseline and 35-cm apertures of the imaging interferometer will allow observations to 8th to 10th mag and resolution of binary components separated by as little as ≈ 200 µas.
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Von Der Lühe, O., S. Solanki, and Th Reinheimer. "Observing stellar surface structure with the ESO-VLT interferometer." Symposium - International Astronomical Union 176 (1996): 147–64. http://dx.doi.org/10.1017/s0074180900083182.
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The ESO Very Large Telescope (VLT) has the capability to coherently combine the light from four 8m telescopes and from smaller Auxiliary telescopes with baselines 4m and 200m (VLT Interferometer or VLTI). The resulting resolution approaches 0.5 milli-arcsec at visible wavelengths and 1 milli-arcsec in the near infra-red. We estimate that about 2000 nearby bright stars can be resolved with these baselines. The surface of about 400 stars, mainly K and M giants, can be mapped with a resolution of a dozen pixels or better across the stellar surface. This resolution permits detailed studies of the structure of stellar atmospheres, their hydrodynamics and magneto-hydrodynamics. VLTI can easily resolve starspots and very likely also convection cells on an active K-type giant at 10pc distance. A marginal detection of the largest starspots on a very active solar-type star at the same distance may be possible, but it appears very unlikely that the surface structure on an inactive solar-type star can be imaged.We present computer simulations of stellar surfaces to study in detail the response of the interferometer to an extended, complex source. First results which simulate the end-to-end process in a simplified manner indicate that useful maps can be produced provided that a sufficient number of baselines are combined in Earth-rotation synthesis mode. We also give arguments that high spectral resolution will prove essential to constrain reconstructed maps.
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Grimani, Catia. "Clues from 4U 0142+61 on supernova fallback disc formation and precession." Monthly Notices of the Royal Astronomical Society 507, no. 1 (July 21, 2021): 261–66. http://dx.doi.org/10.1093/mnras/stab2078.
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ABSTRACT The Nuclear Spectroscopic Telescope Array (NuSTAR) experiment detected a hard X-ray emission (10–70 keV) with a period of 8.68917 s and a pulse-phase modulation at 55 ks, or half this value, from the anomalous X-ray pulsar (AXP) 4U 0142+61. It is shown here that this evidence is naturally explained by the precession of a Keplerian supernova fallback disc surrounding this AXP. It is also found that the precession of discs formed around young neutron stars at distances larger than those considered in the past, may constitute almost neglected sources of gravitational waves with frequencies belonging to the sensitivity bands of the future space interferometers: Laser Interferometer Space Antenna (LISA), Advanced Laser Interferometer Antenna (ALIA), DECi-hertz Interferometer Gravitational wave Observatory (DECIGO), and Big Bang Observer (BBO). In this work, the gravitational wave emission from precessing fallback discs possibly formed around young pulsars such as Crab in a region extending beyond 8 × 107 m from the pulsar surface is estimated. It is also evaluated the role that infrared radiation emission from circumpulsar discs may play in contributing to inverse Compton scattering of TeV energy positrons and electrons. Extensive observational campaigns of disc formation around young and middle-aged pulsars may also contribute to solve the long-standing problem of a pulsar origin for the excess of positrons in cosmic rays observed near the Earth above 7 GeV. In the near future the James Webb Space Telescope, with unprecedented near- and mid-infrared observation capabilities, may provide direct evidence of a large sample of supernova fallback discs.
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Haniff, Chris. "Interferometry of Cool Pulsating Stars." International Astronomical Union Colloquium 155 (1995): 270–80. http://dx.doi.org/10.1017/s025292110003709x.
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AbstractThe drive for high-angular resolution from the ground has led to the development of optical and near infrared interferometric telescopes analogous to radio synthesis arrays. These now provide a diffraction-limited imaging capability well suited to studies of nearby cool giants and supergiants. In this review I summarise the current status of these instruments, their scientific potential for studies of cool pulsating variables (LPVs), and present some recent results that highlight the promise that such methods hold.
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Davis, John. "Overview of Multiple–Aperture Interferometry Binary Star Results from the Southern Hemisphere." Proceedings of the International Astronomical Union 2, S240 (August 2006): 45–53. http://dx.doi.org/10.1017/s174392130700378x.
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AbstractThe first multiple-aperture interferometric study of a binary system, in which the power of combining interferometric and spectroscopic data was demonstrated, was made from the Southern Hemisphere. The observations of α Vir with the Narrabri Stellar Intensity Interferometer (NSII) were combined with spectroscopic and photometric data to yield the mass, radius and luminosity of the primary as well as an accurate distance to the system. The NSII also revealed a number of stars, previously thought to be single, to be binary systems. Several of these systems have subsequently been shown to be spectroscopic binaries.The Sydney University Stellar Interferometer (SUSI) and the European Southern Observatory's Very Large Telescope Interferometer (VLTI) are the two current Southern Hemisphere multiple aperture interferometers. SUSI is being used to determine interferometric orbits for some of the binary systems discovered with the NSII including β Cen and λ Sco and, in combination with spectroscopy, to determine accurate masses for early-type stars and accurate dynamical parallaxes for the systems.The VLTI has operated with three beam-combining instruments, namely VINCI, MIDI and AMBER. The few observations of binary systems that have been made so far are summarised and, while in general they are of a preliminary nature, they demonstrate the potential of the VLTI for binary star studies.One double-lined spectroscopic binary that has been observed with all three Southern Hemisphere instruments is γ2 Vel, which has the brightest Wolf-Rayet star in the sky as its secondary. The observations and preliminary results for the masses of the O-type primary and WC8 secondary and for the distance to the system are summarised.
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Orlov, V. G. "SPECKLE INTERFEROMETRY AT THE OBSERVATORIO ASTRONÓMICO NACIONAL. VII." Revista Mexicana de Astronomía y Astrofísica 57, no. 1 (April 1, 2021): 67–80. http://dx.doi.org/10.22201/ia.01851101p.2021.57.01.04.
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The results of speckle interferometric measurements of binary stars performed during June, 2016 with the 2.1 m telescope at the Observatorio Astronómico Nacional at SPM (México) are given. We report 480 astrometric measurements of 468 double stars systems. The measured angular separations ρ range from 0’’.091 to 5’’.93. Most of the observed pairs (414 out of 468) are close double stars having separations of ρ ≤ 1’’. We confirm as double stars 59 targets and we found 3 new pairs with separation of less than 1’’. Finally, we show that the high resolution autocorrelation function in polar coordinates allows to easily recover astrometric parameters even in the presence of strong telescope aberrations.
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Gallenne, A., G. Pietrzyński, D. Graczyk, N. Nardetto, A. Mérand, P. Kervella, W. Gieren, S. Villanova, R. E. Mennickent, and B. Pilecki. "Fundamental properties of red-clump stars from long-baseline H-band interferometry." Astronomy & Astrophysics 616 (August 2018): A68. http://dx.doi.org/10.1051/0004-6361/201833341.
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Observations of 48 red-clump stars were obtained in the H band with the PIONIER instrument installed at the Very Large Telescope Interferometer. Limb-darkened angular diameters were measured by fitting radial intensity profile I(r) to square visibility measurements. Half the angular diameters determined have formal errors better than 1.2%, while the overall accuracy is better than 2.7%. Average stellar atmospheric parameters (effective temperatures, metallicities and surface gravities) were determined from new spectroscopic observations and literature data and combined with precise Gaia parallaxes to derive a set of fundamental stellar properties. These intrinsic parameters were then fitted to existing isochrone models to infer masses and ages of the stars. The added value from interferometry imposes a better and independent constraint on the R −Teff plane. Our derived values are consistent with previous works, although there is a strong scatter in age between various models. This shows that atmospheric parameters, mainly metallicities and surface gravities, still suffer from a non-accurate determination, limiting constraints on input physics and parameters of stellar evolution models.
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Kluska, J., J. P. Berger, F. Malbet, B. Lazareff, M. Benisty, J. B. Le Bouquin, O. Absil, et al. "A family portrait of disk inner rims around Herbig Ae/Be stars." Astronomy & Astrophysics 636 (April 2020): A116. http://dx.doi.org/10.1051/0004-6361/201833774.
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Context. The innermost astronomical unit (au) in protoplanetary disks is a key region for stellar and planet formation, as exoplanet searches have shown a large occurrence of close-in planets that are located within the first au around their host star. Aims. We aim to reveal the morphology of the disk inner rim using near-infrared interferometric observations with milli-arcsecond resolution provided by near-infrared multitelescope interferometry. Methods. We provide model-independent reconstructed images of 15 objects selected from the Herbig AeBe survey carried out with PIONIER at the Very Large Telescope Interferometer, using the semi-parametric approach for image reconstruction of chromatic objects. We propose a set of methods to reconstruct and analyze the images in a consistent way. Results. We find that 40% of the systems (6/15) are centrosymmetric at the angular resolution of the observations. For the rest of the objects, we find evidence for asymmetric emission due to moderate-to-strong inclination of a disk-like structure for ~30% of the objects (5/15) and noncentrosymmetric morphology due to a nonaxisymmetric and possibly variable environment (4/15, ~27%). Among the systems with a disk-like structure, 20% (3/15) show a resolved dust-free cavity. Finally, we do not detect extended emission beyond the inner rim. Conclusions. The image reconstruction process is a powerful tool to reveal complex disk inner rim morphologies, which is complementary to the fit of geometrical models. At the angular resolution reached by near-infrared interferometric observations, most of the images are compatible with a centrally peaked emission (no cavity). For the most resolved targets, image reconstruction reveals morphologies that cannot be reproduced by generic parametric models (e.g., perturbed inner rims or complex brightness distributions). Moreover, the nonaxisymmetric disks show that the spatial resolution probed by optical interferometers makes the observations of the near-infrared emission (inside a few au) sensitive to temporal evolution with a time-scale down to a few weeks. The evidence of nonaxisymmetric emission that cannot be explained by simple inclination and radiative transfer effects requires alternative explanations, such as a warping of the inner disks. Interferometric observations can therefore be used to follow the evolution of the asymmetry of those disks at an au or sub-au scale.
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Abuter, R., M. Accardo, A. Amorim, N. Anugu, G. Ávila, N. Azouaoui, M. Benisty, et al. "First light for GRAVITY: Phase referencing optical interferometry for the Very Large Telescope Interferometer." Astronomy & Astrophysics 602 (June 2017): A94. http://dx.doi.org/10.1051/0004-6361/201730838.
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GRAVITY is a new instrument to coherently combine the light of the European Southern Observatory Very Large Telescope Interferometer to form a telescope with an equivalent 130 m diameter angular resolution and a collecting area of 200 m2. The instrument comprises fiber fed integrated optics beam combination, high resolution spectroscopy, built-in beam analysis and control, near-infrared wavefront sensing, phase-tracking, dual-beam operation, and laser metrology. GRAVITY opens up to optical/infrared interferometry the techniques of phase referenced imaging and narrow angle astrometry, in many aspects following the concepts of radio interferometry. This article gives an overview of GRAVITY and reports on the performance and the first astronomical observations during commissioning in 2015/16. We demonstrate phase-tracking on stars as faint as mK ≈ 10 mag, phase-referenced interferometry of objects fainter than mK ≈ 15 mag with a limiting magnitude of mK ≈ 17 mag, minute long coherent integrations, a visibility accuracy of better than 0.25%, and spectro-differential phase and closure phase accuracy better than 0.5°, corresponding to a differential astrometric precision of better than ten microarcseconds (μas). The dual-beam astrometry, measuring the phase difference of two objects with laser metrology, is still under commissioning. First observations show residuals as low as 50 μas when following objects over several months. We illustrate the instrument performance with the observations of archetypical objects for the different instrument modes. Examples include the Galactic center supermassive black hole and its fast orbiting star S2 for phase referenced dual-beam observations and infrared wavefront sensing, the high mass X-ray binary BP Cru and the active galactic nucleus of PDS 456 for a few μas spectro-differential astrometry, the T Tauri star S CrA for a spectro-differential visibility analysis, ξ Tel and 24 Cap for high accuracy visibility observations, and η Car for interferometric imaging with GRAVITY.
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Norris, Barnaby R. M., Nick Cvetojevic, Tiphaine Lagadec, Nemanja Jovanovic, Simon Gross, Alexander Arriola, Thomas Gretzinger, et al. "First on-sky demonstration of an integrated-photonic nulling interferometer: the GLINT instrument." Monthly Notices of the Royal Astronomical Society 491, no. 3 (November 23, 2019): 4180–93. http://dx.doi.org/10.1093/mnras/stz3277.
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ABSTRACT The characterization of exoplanets is critical to understanding planet diversity and formation, their atmospheric composition, and the potential for life. This endeavour is greatly enhanced when light from the planet can be spatially separated from that of the host star. One potential method is nulling interferometry, where the contaminating starlight is removed via destructive interference. The GLINT instrument is a photonic nulling interferometer with novel capabilities that has now been demonstrated in on-sky testing. The instrument fragments the telescope pupil into sub-apertures that are injected into waveguides within a single-mode photonic chip. Here, all requisite beam splitting, routing, and recombination are performed using integrated photonic components. We describe the design, construction, and laboratory testing of our GLINT pathfinder instrument. We then demonstrate the efficacy of this method on sky at the Subaru Telescope, achieving a null-depth precision on sky of ∼10−4 and successfully determining the angular diameter of stars (via their null-depth measurements) to milliarcsecond accuracy. A statistical method for analysing such data is described, along with an outline of the next steps required to deploy this technique for cutting-edge science.
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Sasaki, Ayana, Hiroshi Shibai, Taro Matsuo, Takahiro Sumi, Satoshi Itoh, Teruhira Ohyama, Yoshito Tani, Morito Saiki, Takahiro Tsuboi, and Masanao Narita. "Optical Adjustment of the FITE Interferometer." Journal of Astronomical Instrumentation 09, no. 01 (February 10, 2020): 2050002. http://dx.doi.org/10.1142/s2251171720500026.
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We have developed a balloon-borne far-infrared interferometer, the Far-infrared Interferometric Telescope Experiment (FITE). The final goal of spatial resolution was one arcsec at 100[Formula: see text][Formula: see text]m. As a first step, we aimed to achieve a spatial resolution of five arcsecs at 155[Formula: see text][Formula: see text]m with a 6-m baseline. FITE is a two-beam interferometer like Michelson’s stellar interferometer. Positions and attitudes of all mirrors required to have their alignment checked and possibly adjusted before launch and were checked during observation. We had to satisfy three requirements: the coincidence of the phases of each beam (wavefront error), image quality of the two beams at the (common) focus, and no optical path difference between the two beams for celestial objects. In order to achieve the former two requirements, we developed an interferometer adjustment system that used a newly-developed interferometer measurement instrument. This instrument adopted a Shack–Hartmann wavefront sensor to measure wavefront errors of the two off-axis parabolic mirrors, simultaneously. With this system, the adjustment of the FITE interferometer was carried out at the Alice Springs balloon base in Australia as the JAXA’s Australia balloon experiment campaign of 2018. On-site adjustment was successful; wavefront errors of the two off-axis parabolic mirrors were 1.78[Formula: see text][Formula: see text]m and 4.99[Formula: see text][Formula: see text]m (peak-to-valley), and the Hartmann constant was 13 arcsecs. As for the optical path difference, we achieved the requirement by step-wise displacement of a folding plane mirror. Results satisfied the requirements for an interferometer designed for a wavelength of 155[Formula: see text][Formula: see text]m. Improvement of spatial resolution at far-infrared wavelengths is undoubtedly important for research on protoplanetary disks, circumstellar dust shells of late-type stars, and star-forming galaxies. The method we have developed is also useful for future space interferometers.
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Millour, Florentin, Thomas Driebe, Jose H. Groh, Olivier Chesneau, Gerd Weigelt, Adriane Liermann, and Anthony Meilland. "Imaging “Pinwheel” nebulae with optical long-baseline interferometry." Proceedings of the International Astronomical Union 6, S272 (July 2010): 408–9. http://dx.doi.org/10.1017/s1743921311010957.
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AbstractDusty Wolf-Rayet stars are few but remarkable in terms of dust production rates (up to Ṁ = 10−6 M⊙/yr). Infrared excesses associated to mass-loss are found in the sub-types WC8 and WC9. Few WC9d stars are hosting a “pinwheel” nebula, indirect evidence of a companion star around the primary. While few other WC9d stars have a dust shell which has been barely resolved so far, the available angular resolution offered by single telescopes is insufficient to confirm if they also host “pinwheel” nebulae or not. In this article, we present the possible detection of such nebula around the star WR 118. We discuss about the potential of interferometry to image more “pinwheel” nebulae around other WC9d stars.
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Townes, C. H., M. Bester, W. C. Danchi, C. G. Degiacomi, and L. J. Greenhill. "Heterodyne Interferometry in the Infrared." Symposium - International Astronomical Union 158 (1994): 19–25. http://dx.doi.org/10.1017/s0074180900107284.
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The University of California Infrared Spatial Interferometer (ISI) for the 10 μm wavelength region is briefly described along with results obtained on prominent stars and on atmospheric phenomena. The system has two movable telescopes of 1.65 m aperture. It operates in principle like a modern radio interferometer, using heterodyne detection, CO2 laser local oscillators, RF delay lines, and lobe rotation to maintain a fixed-frequency fringe rate.Rather extensive measurements have been made on atmospheric pathlength or phase fluctuation characteristics which show substantial deviations from the Kolmogorov-Taylor model, fortunately in a direction favoring adaptive optics, long baselines, and the use of infrared wavelengths. Outer scales as small as about 10 meters occur under good seeing conditions. Visibility results on 13 stars show that 6 of them have dust shells rather far from the star and give evidence for episodic emission of gas. Others of the 13 stars also vary with time, but are characterized by more continuous emission and dust formation near the stars at temperatures as high as 1300 K.
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Balega, I. I., Y. Y. Balega, V. A. Vasyuk, and J. J. McManus. "Double and Multiple Star Speckle Observations at the 6-m Telescope." International Astronomical Union Colloquium 135 (1992): 469–76. http://dx.doi.org/10.1017/s0252921100006989.
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During the last 15 years more than 9,000 speckle interferometric measurements of binary stars have been collected using large optical telescopes (McAlister & Hartkopf 1988). Among them a significant contribution to the world speckle data has been made by the 6-m telscope near Zelenchuk. Up to now this instrument provides the maximal spatial resolution for single–aperture telescopes. First speckle images of the binary Capella were recorded at the telescope in 1977 (Balega & Tikhonov 1977), but we spent 5 more years to create special television techniques for photon counting and digital means for image processing before we started the regular interferometric program of binary observations in the wide range of stellar magnitudes. At first, the measurements were conducted in cooperation with French astronomers from the Centre d’Etudes et de Recherches Geodynamiques et Astronomiques using the optical camera and the television detector developed by Blazit et al. (1977). Since 1983 our equipment has been in use. The program of observations was oriented upon the traditional problems of multiple star speckle interferometry:1.Determination of stellar distances and masses for different types of binaries whose orbital elements can be derived. This includes already known fast visual and astrometric pairs with undetermined orbits, spectroscopic binaries that can be resolved directly, and newly discovered interferometric pairs which show fast orbital motion. The main attention was devoted to the late–type dwarfs in the vicinity of the Sun.2.Search for the secondary components whose existence could explain anomalies of stellar spectra or photometry (stars with composite spectra, occultation binaries, etc.)3.Study of unusual binaries (symbiotic stars, binaries with relativistic components, such as SS 433, etc.)
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GENET, R. M. "PORTABLE SPECKLE INTERFEROMETRY CAMERA SYSTEM." Journal of Astronomical Instrumentation 02, no. 02 (December 2013): 1340008. http://dx.doi.org/10.1142/s2251171713400084.
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Speckle interferometry of close double stars avoids seeing limitations through a series of diffraction-limited high speed observations made faster than the atmospheric coherence time scale. Electron multiplying CCD cameras have low read noise at high read speeds, making them ideal for speckle interferometry. A portable speckle camera system was developed based on relatively low cost, off-the-shelf components. The camera's modular components can be exchanged to adapt the system to a wide range of telescopes.
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Lopez, B., S. Lagarde, R. G. Petrov, W. Jaffe, P. Antonelli, F. Allouche, P. Berio, et al. "MATISSE, the VLTI mid-infrared imaging spectro-interferometer." Astronomy & Astrophysics 659 (March 2022): A192. http://dx.doi.org/10.1051/0004-6361/202141785.
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Context. Optical interferometry is at a key development stage. The Very Large Telescope Interferometer (VLTI) has established a stable, robust infrastructure for long-baseline interferometry that is usable by general astronomical observers. The present second-generation instruments offer a wide wavelength coverage and improved performance. Their sensitivity and measurement accuracy lead to data and images of high reliability. Aims. We have developed the Multi AperTure mid-Infrared SpectroScopic Experiment (MATISSE) to access, for the first time, high resolution imaging in a wide spectral domain. Many front-line topics are explored with this new equipment, including: stellar activity and mass loss; planet formation and evolution in the gas and dust disks around young stars; and environment interaction and accretion processes around super massive black holes in active galactic nuclei. Methods. The instrument is a spectro-interferometric imager in the transmission windows called L, M, and N, from 2.8 to 13.0 microns, combining four optical beams from the VLTI’s unit or auxiliary telescopes. Its concept, related observing procedure, data reduction, and calibration approach, is the product of 30 years of instrumental research and has benefitted from the expertise developed in the frame of the VLTI’s first generation instruments. The instrument utilises a multi-axial beam combination that delivers spectrally dispersed fringes. The signal provides the following quantities at several spectral resolutions: photometric flux, coherent fluxes, visibilities, closure phases, wavelength differential visibilities and phases, and aperture-synthesis imaging. Results. This article provides an overview of the physical principle of the instrument and its functionalities. The motivation of the choice of the instrumental concept and the characteristics of the delivered signal are detailed with a description of the observing modes and of their performance limit. MATISSE offers four spectral resolutions in L&M bands, namely 30, 500, 1000 and 3400, and 30 and 220 in the N band, and it provides an angular resolution down to 3 mas for the shortest wavelengths. The MATISSE stand-alone sensitivity limits are 60 mJy in L and 300 mJy in N. The paper gives details of the sensitivity limits for the different measurables and their related precision criteria, considering telescope configurations and spectral resolutions. We also discuss the gain provided with the GRA4MAT fringe tracker. An ensemble of data and reconstructed images illustrate the first acquired key observations. Conclusions. The instrument has been in operation at Cerro Paranal, ESO, Chile, since 2018, and has been open for science use by the international community since April 2019. The first scientific results are being published now.
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Slee, O. B., G. J. Nelson, R. T. Stewart, Alan E. Wright, David L. Jauncey, A. E. Vaughan, M. I. Large, J. D. Bunton, W. L. Peters, and S. G. Ryan. "Outstanding Stellar Microwave Flares in 1986." Publications of the Astronomical Society of Australia 7, no. 1 (1987): 55–59. http://dx.doi.org/10.1017/s1323358000021846.
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AbstractWe describe bright microwave events that were first detected with the Parkes 64-m telescope at 8.4 or 22 GHz from six active-chromosphere stars. In some flares spectral data were obtained over a large frequency range from simultaneous measurements with the Parkes reflector (8.4 or 22 GHz), the Tidbinbilla interferometer (8.4 and 2.29 GHz), the Fleurs synthesis telescope (1.42 GHz) and the Molonglo Observatory synthesis telescope (0.843 GHz). Data on circular polarization were obtained from the Parkes observations at 8.4 GHz.The stars were in a wide variety of evolutionary states, ranging from a single pre-main-sequence star (HD 36705), two RS CVn binaries (HD 127535, HD 128171), an Algol (HD 132742) and two apparently single K giants (HD 32918 and HD 196818). Their high brightness temperatures, positive spectral indices and low polarization are consistent with optically thick gyrosynchrotron emission from mildly relativistic electrons with average energies 0.5 to 3 MeV gyrating in inhomogeneous magnetic fields of 5 to 100 G.
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McAlister, H. A. "Commission 26 : Double and Multiple Stars." Transactions of the International Astronomical Union 21, no. 1 (1991): 243–46. http://dx.doi.org/10.1017/s0251107x00010075.
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The observational study of double and multiple stars is traditionally seen as comprised of several specialized subfields, each defined by particular observational selection effects. Improvements in increased precision and accuracy, higher resolution, higher signal-to-noise ratios, greater sensitivity etc.), are leading the study of double stars to a truly coherent field. Significant advances in ground-based spectroscopy and interferometry provide a framework from which we can prepare for the future. The contributions to be made from space are currently in a state of uncertainty as we await results from the Hubble Space Telescope and Hipparcos.
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Varga, J., P. Ábrahám, L. Chen, Th Ratzka, K. É. Gabányi, Á. Kóspál, A. Matter, et al. "VLTI/MIDI atlas of disks around low- and intermediate-mass young stellar objects." Astronomy & Astrophysics 617 (September 2018): A83. http://dx.doi.org/10.1051/0004-6361/201832599.
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Context. Protoplanetary disks show large diversity regarding their morphology and dust composition. With mid-infrared interferometry the thermal emission of disks can be spatially resolved, and the distribution and properties of the dust within can be studied. Aims. Our aim is to perform a statistical analysis on a large sample of 82 disks around low- and intermediate-mass young stars, based on mid-infrared interferometric observations. We intend to study the distribution of disk sizes, variability, and the silicate dust mineralogy. Methods. Archival mid-infrared interferometric data from the MIDI instrument on the Very Large Telescope Interferometer are homogeneously reduced and calibrated. Geometric disk models are used to fit the observations to get spatial information about the disks. An automatic spectral decomposition pipeline is applied to analyze the shape of the silicate feature. Results. We present the resulting data products in the form of an atlas, containing N band correlated and total spectra, visibilities, and differential phases. The majority of our data can be well fitted with a continuous disk model, except for a few objects, where a gapped model gives a better match. From the mid-infrared size–luminosity relation we find that disks around T Tauri stars are generally colder and more extended with respect to the stellar luminosity than disks around Herbig Ae stars. We find that in the innermost part of the disks (r ≲ 1 au) the silicate feature is generally weaker than in the outer parts, suggesting that in the inner parts the dust is substantially more processed. We analyze stellar multiplicity and find that in two systems (AB Aur and HD 72106) data suggest a new companion or asymmetric inner disk structure. We make predictions for the observability of our objects with the upcoming Multi-AperTure mid-Infrared SpectroScopic Experiment (MATISSE) instrument, supporting the practical preparations of future MATISSE observations of T Tauri stars.
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Baudoin, R., P. Darré, J. T. Gomes, M. Fabert, L. Grossard, L. Delage, F. Reynaud, et al. "ALOHA 1.55μm Implementation on the CHARA Telescope Array: On-Sky Sensitivity Tests." Journal of Astronomical Instrumentation 05, no. 03 (September 2016): 1650006. http://dx.doi.org/10.1142/s2251171716500069.
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We intend to implement the ALOHA at 1.55[Formula: see text][Formula: see text]m up-conversion interferometer on the CHARA Array. After a full laboratory investigation, a sensitivity evaluation is conducted on several stars using a single interferometric arm in a photometric mode. The on-sky photometric results allows us to calibrate a numerical simulation of the interferometric configuration, and to predict the future performance of ALOHA at 1.55[Formula: see text][Formula: see text]m as a function of the seeing conditions.
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Wittkowski, Markus, David A. Boboltz, Malcolm D. Gray, Elizabeth M. L. Humphreys, Iva Karovicova, and Michael Scholz. "Radio and IR interferometry of SiO maser stars." Proceedings of the International Astronomical Union 8, S287 (January 2012): 209–16. http://dx.doi.org/10.1017/s1743921312006989.
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AbstractRadio and infrared interferometry of SiO maser stars provide complementary information on the atmosphere and circumstellar environment at comparable spatial resolution. Here, we present the latest results on the atmospheric structure and the dust condensation region of AGB stars based on our recent infrared spectro-interferometric observations, which represent the environment of SiO masers. We discuss, as an example, new results from simultaneous VLTI and VLBA observations of the Mira variable AGB star R Cnc, including VLTI near- and mid-infrared interferometry, as well as VLBA observations of the SiO maser emission toward this source. We present preliminary results from a monitoring campaign of high-frequency SiO maser emission toward evolved stars obtained with the APEX telescope, which also serves as a precursor of ALMA images of the SiO emitting region. We speculate that large-scale long-period chaotic motion in the extended molecular atmosphere may be the physical reason for observed deviations from point symmetry of atmospheric molecular layers, and for the observed erratic variability of high-frequency SiO maser emission.
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Wittkowski, M., G. Rau, A. Chiavassa, S. Höfner, M. Scholz, P. R. Wood, W. J. de Wit, F. Eisenhauer, X. Haubois, and T. Paumard. "VLTI-GRAVITY measurements of cool evolved stars." Astronomy & Astrophysics 613 (May 2018): L7. http://dx.doi.org/10.1051/0004-6361/201833029.
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Context. Dynamic model atmospheres of Mira stars predict variabilities in the photospheric radius and in atmospheric molecular layers which are not yet strongly constrained by observations. Aims. Here we measure the variability of the oxygen-rich Mira star R Peg in near-continuum and molecular bands. Methods. We used near-infrared K-band spectro-interferometry with a spectral resolution of about 4000 obtained at four epochs between post-maximum and minimum visual phases employing the newly available GRAVITY beam combiner at the Very Large Telescope Interferometer (VLTI). Results. Our observations show a continuum radius that is anti-correlated with the visual lightcurve. Uniform disc (UD) angular diameters at a near-continuum wavelength of 2.25 μm are steadily increasing with values of 8.7 ± 0.1 mas, 9.4 ± 0.1 mas, 9.8 ± 0.1 mas, and 9.9 ± 0.1 mas at visual phases of 0.15, 0.36, 0,45, 0.53, respectively. UD diameters at a bandpass around 2.05 μm, dominated by water vapour, follow the near-continuum variability at larger UD diameters between 10.7 mas and 11.7 mas. UD diameters at the CO 2–0 bandhead, instead, are correlated with the visual lightcurve and anti-correlated with the near-continuum UD diameters, with values between 12.3 mas and 11.7 mas. Conclusions. The observed anti-correlation between continuum radius and visual lightcurve is consistent with an earlier study of the oxygen-rich Mira S Lac, and with recent 1D CODEX dynamic model atmosphere predictions. The amplitude of the variation is comparable to the earlier observations of S Lac, and smaller than predicted by CODEX models. The wavelength-dependent visibility variations at our epochs can be reproduced by a set of CODEX models at model phases between 0.3 and 0.6. The anti-correlation of water vapour and CO contributions at our epochs suggests that these molecules undergo different processes in the extended atmosphere along the stellar cycle. The newly available GRAVITY instrument is suited to conducting longer time series observations, which are needed to provide strong constraints on the model-predicted intra- and inter-cycle variability.
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Kammerer, Jens, and Sascha P. Quanz. "Simulating the exoplanet yield of a space-based mid-infrared interferometer based on Kepler statistics." Astronomy & Astrophysics 609 (December 22, 2017): A4. http://dx.doi.org/10.1051/0004-6361/201731254.
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Aims. We predict the exoplanet yield of a space-based mid-infrared nulling interferometer using Monte Carlo simulations. We quantify the number and properties of detectable exoplanets and identify those target stars that have the highest or most complete detection rate. We investigate how changes in the underlying technical assumptions and uncertainties in the underlying planet population impact the scientific return. Methods. We simulated 2000 exoplanetary systems, based on planet occurrence statistics from Kepler with randomly orientated orbits and uniformly distributed albedos around each of 326 nearby (d< 20 pc) stars. Assuming thermal equilibrium and blackbody emission, together with the limiting spatial resolution and sensitivity of our simulated instrument in the three specific bands 5.6, 10.0, and 15.0 μm, we quantified the number of detectable exoplanets as a function of their radii and equilibrium temperatures. Results. Approximately [see formula in PDF] exoplanets, with radii 0.5 REarth ≤ Rp ≤ 6 REarth, were detected in at least one band and half were detected in all three bands during ~0.52 years of mission time assuming throughputs 3.5 times worse than those for the James Webb Space Telescope and ~40% overheads. Accounting for stellar leakage and (unknown) exozodiacal light, the discovery phase of the mission very likely requires 2−3 years in total. The uncertainties in planet yield are dominated by uncertainties in the underlying planet population, but the distribution of the Bond albedos also has a significant impact. Roughly 50% of the detected planets orbit M stars, which also have the highest planet yield per star; the other 50% orbit FGK stars, which show a higher completeness in the detectability. Roughly 85 planets could be habitable (0.5 REarth ≤ Rp ≤ 1.75 REarth and 200 K ≤ Teq ≤ 450 K) and are prime targets for spectroscopic observations in a second mission phase. Comparing these results to those of a large optical/near-infrared telescope, we find that a mid-infrared interferometer would detect more planets and the number of planets depends less strongly on the wavelength. Conclusions. An optimized space-based nulling interferometer operating in the mid-infrared would deliver an unprecedented dataset for the characterization of (small) nearby exoplanets including dozens of potentially habitable worlds.
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Groh, Jose H. "Zooming into Eta Carinae with interferometry." Proceedings of the International Astronomical Union 9, S307 (June 2014): 267–72. http://dx.doi.org/10.1017/s1743921314006917.
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AbstractShaped by strong mass loss, rapid rotation, and/or the presence of a close companion, the circumstellar environment around the most massive stars is complex and anything but spherical. Here we provide a brief overview of the high spatial resolution observations of Eta Carinae performed with the Very Large Telescope Interferometer (VLTI). Special emphasis is given to discuss VLTI/AMBER and VLTI/VINCI observations, which directly resolve spatial scales comparable to those where mass loss originates. Studying scales as small as a few milli-arcseconds allows us to investigate kinematical effects of rotation and binarity in more detail than ever before.
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Sakamoto, Kazushi, Takeo Minezaki, Keiichi Wada, Sachiko Okumura, and Yukiyasu Kobayashi. "Gas Dynamics and Active Phenomena in Galactic Nuclei: M100 and M94." International Astronomical Union Colloquium 157 (1996): 247–49. http://dx.doi.org/10.1017/s0252921100049861.
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Since molecular gas fuels AGNs and molecular clouds form stars, understanding of molecular gas dynamics is a key to the understanding of active phenomena (such as starbursts and AGNs) in galactic nuclei. To study gas dynamics in weakly barred galaxies, we made CO interferometry (to trace gas) and NIR imaging (to trace stars) toward two nearby SAB galaxies M100 and M94. Each galaxy has a small stellar nuclear bar and also has an outer bar or oval distortion, thus suitable for the study of gas dynamics in a barred gravitational potential. Observations were made using Nobeyama Millimeter Array (NMA) and the IRcamera PICNIC installed at the ISAS 1.3 m telescope.
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Escudero Sanz, Isabel, Astrid Heske, and Jeffrey C. Livas. "A telescope for LISA – the Laser Interferometer Space Antenna." Advanced Optical Technologies 7, no. 6 (December 19, 2018): 395–400. http://dx.doi.org/10.1515/aot-2018-0044.
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Abstract Gravitational waves are a prediction of Einstein’s general relativity theory. In autumn 2017, the Laser Interferometer Gravitational-Wave Observatory (LIGO; https://www.ligo.caltech.edu/) experiment reported the first detection of gravitational waves in addition to electromagnetic radiation from the collision of two neutron stars. This marks the first time that a cosmic event has been viewed in both gravitational waves and light and opens the door to a new type of astronomical observatory based on gravitational waves. The gravitational wave spectrum covers a broad span of frequencies and requires both space- and ground-based observatories to cover the full range. Space-based gravitational wave observatories, such as the proposed Laser Interferometer Space Antenna (LISA), operate at frequencies between 0.1 mHz and 1 Hz and complement the frequency range of 30–1000 Hz accessible by ground-based gravitational wave observatories, such as LIGO. A rich array of high-energy astrophysical sources is expected in the LISA measurement band. LISA was selected in 2017 as the third large mission of the Cosmic Vision program of the European Space Agency. The National Aeronautics and Space Administration will collaborate on both the scientific and technical aspects of this mission. This paper addresses the design of the optical telescope as an essential component of LISA’s long-distance interferometric measurement system.
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Gies, Douglas R. "Taking the Measure of Massive Stars and their Environments with the CHARA Array Long-baseline Interferometer." Proceedings of the International Astronomical Union 12, S329 (November 2016): 156–60. http://dx.doi.org/10.1017/s1743921317002393.
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AbstractMost massive stars are so distant that their angular diameters are too small for direct resolution. However, the observational situation is now much more favorable, thanks to new opportunities available with optical/IR long-baseline interferometry. The Georgia State University Center for High Angular Resolution Astronomy Array at Mount Wilson Observatory is a six-telescope instrument with a maximum baseline of 330 meters, which is capable of resolving stellar disks with diameters as small as 0.2 milliarcsec. The distant stars are no longer out of range, and many kinds of investigations are possible. Here we summarize a number of studies involving angular diameter measurements and effective temperature estimates for OB stars, binary and multiple stars (including the σ Orionis system), and outflows in Luminous Blue Variables. An enlarged visitors program will begin in 2017 that will open many opportunities for new programs in high angular resolution astronomy.
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Damljanovic, G., O. Vince, and S. Boeva. "Gaia science alerts and the observing facilities of the Serbian-Bulgarian mini-network telescopes." Serbian Astronomical Journal, no. 188 (2014): 85–93. http://dx.doi.org/10.2298/saj1488085d.
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The astrometric European Space Agency (ESA) Gaia mission was launched in December 19, 2013. One of the tasks of the Gaia mission is production of an astrometric catalog of over one billion stars and more than 500000 extragalactic sources. The quasars (QSOs), as extragalactic sources and radio emitters, are active galactic nuclei objects (AGNs) whose coordinates are well determined via Very Long Baseline Interferometry (VLBI) technique and may reach sub-milliarcsecond accuracy. The QSOs are the defining sources of the quasi-inertial International Celestial Reference Frame (ICRF) because of their core radio morphology, negligible proper motions (until sub-milliarcsecond per year), and apparent point-like nature. Compact AGNs, visible in optical domain, are useful for a direct link of the future Gaia optical reference frame with the most accurate radio one. Apart from the above mentioned activities, Gaia has other goals such as follow-up of transient objects. One of the most important Gaia's requirements for photometric alerts is a fast observation and reduction response, that is, submition of observations within 24 hours. For this reason we have developed a pipeline. In line with possibilities of our new telescope (D(cm)/F(cm)=60/600) at the Astronomical Station Vidojevica (ASV, of the Astronomical Observatory in Belgrade), we joined the Gaia-Follow-Up Network for Transients Objects (Gaia-FUN-TO) for the photometric alerts. Moreover, in view of the cooperation with Bulgarian colleagues (in the frst place, SV), one of us (GD) initiated a local mini-network of Serbian { Bulgarian telescopes useful for the Gaia-FUN-TO and other astronomical purposes. During the next year we expect a new 1.4 m telescope at ASV site. The speed of data processing (from observation to calibration server) could be one day. Here, we present an overview of our activities in the Gaia-FUN-TO which includes establishing Serbian { Bulgarian mini-network (of five telescopes at three sites, ASV in Serbia, Belogradchik and Rozhen in Bulgaria), the Gaia-FUN-TO test observations, and some results.