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Journal articles on the topic 'Star system spectroscopy'
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1
Hinkle, Kenneth H., Stephen T. Ridgway, and Francis C. Fekel. "Infrared Spectroscopy of Multiple Star Systems." International Astronomical Union Colloquium 135 (1992): 149–51. http://dx.doi.org/10.1017/s0252921100006266.
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AbstractUp to this time infrared spectroscopy has been only occasionally used in binary star research due to both the insensitivity of infrared spectrographs and the difficulty of getting observing time on a limited number of spectrographs. However, infrared spectroscopy has a number of interesting applications in binary star research. We present an example of an application to the long-period symbiotic system CH Cyg. Due to the recent development of infrared arrays, infrared spectroscopy (1) is becoming available at a much larger number of telescopes and (2) in the 1.0-2.5 μm region is capable of going to limiting magnitudes nearly as faint as those reached by CCD’s.
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Maíz Apellániz, J., R. H. Barbá, S. Simón-Díaz, A. Sota, E. Trigueros Páez, J. A. Caballero, and E. J. Alfaro. "Lucky Spectroscopy, an equivalent technique to Lucky Imaging." Astronomy & Astrophysics 615 (July 2018): A161. http://dx.doi.org/10.1051/0004-6361/201832885.
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Context. Many massive stars have nearby companions whose presence hamper their characterization through spectroscopy. Aims. We want to obtain spatially resolved spectroscopy of close massive visual binaries to derive their spectral types. Methods. We obtained a large number of short long-slit spectroscopic exposures of five close binaries under good seeing conditions. We selected those with the best characteristics, extracted the spectra using multiple-profile fitting, and combined the results to derive spatially separated spectra. Results. We demonstrate the usefulness of Lucky Spectroscopy by presenting the spatially resolved spectra of the components of each system, in two cases with separations of only ~0.′′3. Those are δ Ori Aa+Ab (resolved in the optical for the first time) and σ Ori AaAb+B (first time ever resolved). We also spatially resolve 15 Mon AaAb+B, ζ Ori AaAb+B (both previously resolved with GOSSS, the Galactic O-Star Spectroscopic Survey), and η Ori AaAb+B, a system with two spectroscopic B+B binaries and a fifth visual component. The systems have in common that they are composed of an inner pair of slow rotators orbited by one or more fast rotators, a characteristic that could have consequences for the theories of massive star formation.
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Charles, P. A. "Black-Hole Systems: Optical Spectroscopy and IR Photometry." Symposium - International Astronomical Union 165 (1996): 341–50. http://dx.doi.org/10.1017/s0074180900055807.
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The X-ray transient systems have provided the first opportunities for detailed studies of the mass losing star in low-mass X-ray binaries. During X-ray quiescence the cool star is the dominant light source in the red and near-IR. Optical spectroscopy yields the mass function (itself a lower limit to the compact-object mass), the rotational broadening leads to the mass ratio, q (assuming only that the star fills its Roche lobe), and the IR ellipsoidal light curve gives the system inclination (for high q). In such cases, a complete solution to the system parameters is possible, and this has been performed for A 0620-00 (V616 Mon) and GS 2023+338 (V404 Cyg), leading to the first accurate black-hole masses (which are in the range 10–12 M⊙).
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Moffat, Anthony F. J. "Time-resolved optical-UV spectroscopy of colliding wind effects." Symposium - International Astronomical Union 193 (1999): 278–88. http://dx.doi.org/10.1017/s0074180900205548.
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It is in the ultraviolet-optical domain where the strongest known emission lines arise in hot star winds. In the case of hot-star binaries, culminating in the relatively common, strong-wind WR+O systems, similar line-emission is seen in the cooling flows downstream from the highly compressed, X-ray emitting heads of the bow shock regions produced when the two winds collide. Time-resolved UV-optical spectroscopy of these flows around a complete orbit can provide important constraints not only on the colliding wind process itself, but also on the winds and the orbit. Spectroscopic wind-wind collision effects have now been seen in every relatively close WR+O system (P ≲ 100 d) that has been adequately observed so far.
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Hajduk, Marcin, Peter A. M. van Hoof, and Albert A. Zijlstra. "GLMP 160 – the first [WR] star in a binary." Proceedings of the International Astronomical Union 7, S283 (July 2011): 382–83. http://dx.doi.org/10.1017/s1743921312011532.
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AbstractWe discuss the results of the search for [WR] central stars in binary systems. GLMP 160 is the first [WR] central star in a binary system known. We analyze photometry, spectroscopy and imaging of this system.
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Walton, N. A., J. R. Walsh, and S. R. Pottasch. "Imaging and Spectroscopy of Abell 63 (UU SGE)." Symposium - International Astronomical Union 155 (1993): 394. http://dx.doi.org/10.1017/s0074180900171839.
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UU Sge, the eclipsing binary central star (Bond et al, 1978) of the low-surface-brightness planetary nebula (PN) Abell 63, has been observed spectroscopically in the visible throughout its 11.2 hour period and especially during the minimum. A spectral determination of the binary system has been made. The primary hot central star is an ‘O’ type PN nucleus of temperature ≈40,000 K, consistent with the low excitation of the nebular spectrum (e.g. no He ii 4686Å nebular emission detected). From the spectrum at minimum light, the secondary star appears to be a cool dwarf star around G7. Measurement of the magnitude of the secondary during the eclipse of the primary enabled the distance to the PN to be directly determined as 3.6 kpc. For this distance the luminosity of the hot star is approximately 4 320 L⊙, in good agreement with evolutionary tracks for (single) PN nuclei. Deep CCD images of Abell 63 show it has a ‘butterfly’ morphology implying that the close binary central system may have had a strong effect on the nebula shaping. The paper describing this work has been submitted (Walton et al, 1992).
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Skopal, A., D. Chochol, A. Vittone, and A. Mammano. "Photometric and Spectroscopic Variations of the Symbiotic Star EG Andromedae." International Astronomical Union Colloquium 103 (1988): 289–90. http://dx.doi.org/10.1017/s0252921100103665.
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EG And is a symbiotic binary system. The cool component is an M3 III star, the hot one is a subdwarf with temperature 60 250 K and luminosity 1.45 L⊙ (Boyarchuk, 1985). The eclipsing nature of the system suggested from UV spectroscopy by Oliversen et al. (1985) was confirmed photometrically by Chochol et al. (1987). The circular spectroscopic orbit of cool component determined by Oliversen et al. (1985) supposing the orbital period 470 days leads to f(m) = 3.2×10−2 M⊙ and detached configuration.
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Hummel, Christian A. "Imaging and Modeling of Double Stars with the Navy Prototype Optical Interferometer: a Continuation of the Mark III Double Star Program." International Astronomical Union Colloquium 170 (1999): 416–21. http://dx.doi.org/10.1017/s0252921100048855.
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AbstractWe present results from the new Navy Prototype Optical Interferometer (NPOI) – the orbit of the double star Mizar A and measurements of Matar – which are compared to an orbit determined with the predecessor of NPOI, the Mark III Interferometer. Uncertainties of the orbital inclination are between 0.1 and 0.3 degrees; those of the semi-major axis are less than 0.5 percent. We determine the component masses and other parameters of the double star system, including relative photometry, directly through a fit to a combination of interferometric and spectroscopic data. Algorithms were developed to handle any hierarchical stellar system.We describe plans for the study of spectroscopic double stars with NPOI, which draw from our experience with the Mark III binary program. This program yielded orbits of 26 stars, of which 17 were published with mass determinations of 24 components using spectroscopy. The accuracy of the physical parameters were often limited by the spectroscopy. We show that in order to benefit from the high precision of the interferometric observations, new high-precision spectroscopic observations, combined with improved algorithms for the detection of the secondaries, are required.
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Hinkle, Kenneth H., Francis C. Fekel, Richard R. Joyce, Joanna Mikołajewska, Cezary Gałan, and Thomas Lebzelter. "Infrared Spectroscopy of Symbiotic Stars. XII. The Neutron Star SyXB System 4U 1700+24 = V934 Herculis." Astrophysical Journal 872, no. 1 (February 8, 2019): 43. http://dx.doi.org/10.3847/1538-4357/aafba5.
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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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Kochukhov, O., C. Johnston, J. Labadie-Bartz, S. Shetye, T. A. Ryabchikova, A. Tkachenko, and M. E. Shultz. "V772 Cas: an ellipsoidal HgMn star in an eclipsing binary." Monthly Notices of the Royal Astronomical Society 500, no. 2 (November 10, 2020): 2577–89. http://dx.doi.org/10.1093/mnras/staa3472.
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ABSTRACT The late B-type star V772 Cas (HD 10260) was previously suspected to be a rare example of a magnetic chemically peculiar star in an eclipsing binary system. Photometric observations of this star obtained by the TESS satellite show clear eclipses with a period of 5.0137 d accompanied by a significant out-of-eclipse variation with the same period. High-resolution spectroscopy reveals V772 Cas to be an SB1 system, with the primary component rotating about a factor two slower than the orbital period and showing chemical peculiarities typical of non-magnetic HgMn chemically peculiar stars. This is only the third eclipsing HgMn star known and, owing to its brightness, is one of the very few eclipsing binaries with chemically peculiar components accessible to detailed follow-up studies. Taking advantage of the photometric and spectroscopic observations available for V772 Cas, we performed modelling of this system with the phoebe code. This analysis provided fundamental parameters of the components and demonstrated that the out-of-eclipse brightness variation is explained by the ellipsoidal shape of the evolved, asynchronously rotating primary. This is the first HgMn star for which such variability has been definitively identified.
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P. Huenemoerder, David, Bram Boroson, Norbert S. Schulz, Claude R. Canizares, Derek L. Buzasi, Heather L. Preston, and Joel H. Kastner. "Stellar Coronal Spectroscopy with the Chandra HETGS." Symposium - International Astronomical Union 219 (2004): 238–42. http://dx.doi.org/10.1017/s0074180900182178.
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Spectroscopy with the Chandra High Energy Transmission Grating Spectrometer (HETGS) provides details on X-ray emission and activity from young and cool stars through resolution of emission lines from a variety of ions. We are beginning to see trends in activity regarding abundances, emission measures, and variability. Here we contrast spectra of TV Crt, a weak-lined T Tauri star (WTT), with TW Hya, a Classical T Tauri star (CTT). TV Crt has a spectrum more like magnetic activity driven coronae, relative to the TW Hya spectrum, which we have interpreted as due to accretion-produced X-rays. We have also observed the long period system, IM Pegasi to search for rotational modulation, and to compare activity in a long period active binary to shorter period systems and to the pre-main sequence stars. We detected no rotational modulation, but did see long-duration flares.
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Robertson, J. G., T. R. Bedding, C. Aerts, C. Waelkens, R. G. Marson, and J. R. Barton. "Interferometry and spectroscopy of Cen: a Cephei star in a binary system." Monthly Notices of the Royal Astronomical Society 302, no. 2 (January 11, 1999): 245–52. http://dx.doi.org/10.1046/j.1365-8711.1999.02068.x.
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Herath, Mahesh, Tobias C. Hinse, John H. Livingston, Jesús Hernández, Daniel F. Evans, Robert Wells, Saraj Gunesekera, et al. "Two temperate sub-Neptunes transiting the star EPIC 212737443." Monthly Notices of the Royal Astronomical Society 488, no. 1 (June 14, 2019): 536–46. http://dx.doi.org/10.1093/mnras/stz1641.
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ABSTRACT We report the validation of a new planetary system around the K3 star EPIC 212737443 using a combination of K2 photometry, follow-up high-resolution imaging and spectroscopy. The system consists of two sub-Neptune sized transiting planets with radii of 2.6R⊕ and 2.7R⊕, with orbital periods of 13.6 and 65.5 d, equilibrium temperatures of 536 and 316 K, respectively. In the context of validated K2 systems, the outer planet has the longest precisely measured orbital period, as well as the lowest equilibrium temperature for a planet orbiting a star of spectral type earlier than M. The two planets in this system have a mutual Hill radius of ΔRH = 36, larger than most other known transiting multiplanet systems, suggesting the existence of another (possibly non-transiting) planet, or that the system is not maximally packed.
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van den Besselaar, E. J. M., R. Greimel, L. Morales-Rueda, G. Nelemans, J. R. Thorstensen, T. R. Marsh, V. S. Dhillon, et al. "DE CVn: A Bright, Eclipsing Red Dwarf – White Dwarf Binary." Proceedings of the International Astronomical Union 2, S240 (August 2006): 105–8. http://dx.doi.org/10.1017/s1743921307003882.
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AbstractDE CVn is a relatively unstudied eclipsing binary where one of the components is an M dwarf and the other is a white dwarf. Its brightness makes it an ideal system for a detailed study in the context of common-envelope evolution of a detached white dwarf – red dwarf binary with a relatively short orbital period (∼8.7 hours). We present a detailed study of the basic parameters (e.g. orbital period, components' masses and spectral types) for this system from photometric and spectroscopic studies. The eclipses observed during several photometric observing runs were used to derive the ephemeris. We have used spectroscopic data to derive the radial velocity variations of the emission lines and these are used to determine the components' masses and the orbital separation. The secondary component in DE CVn is an M3 main-sequence star and the primary star, which only contributes to the blue continuum, is a cool white dwarf with a temperature of ∼8000 K. From the photometry and spectroscopy together, we have set a limit on the binary inclination. This system is a post-common-envelope system where the progenitor of the present day white dwarf was a low-mass star (M≤2M⊙). The time before DE CVn becomes a semi-detached system is longer than the Hubble time.
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Murgas, F., E. Pallé, H. Parviainen, G. Chen, L. Nortmann, G. Nowak, A. Cabrera-Lavers, and N. Iro. "The GTC exoplanet transit spectroscopy survey." Astronomy & Astrophysics 605 (September 2017): A114. http://dx.doi.org/10.1051/0004-6361/201730937.
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Context. Transiting planets offer an excellent opportunity for characterizing the atmospheres of extrasolar planets under very different conditions from those found in our solar system. Aims. We are currently carrying out a ground-based survey to obtain the transmission spectra of several extrasolar planets using the 10 m Gran Telescopio Canarias. In this paper we investigate the extrasolar planet WASP-48b, a hot Jupiter orbiting around an F-type star with a period of 2.14 days. Methods. We obtained long-slit optical spectroscopy of one transit of WASP-48b with the Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy (OSIRIS) spectrograph. We integrated the spectrum of WASP-48 and one reference star in several channels with different wavelength ranges, creating numerous color light curves of the transit. We fit analytic transit curves to the data taking into account the systematic effects present in the time series in an effort to measure the change of the planet-to-star radius ratio (Rp/Rs) across wavelength. The change in transit depth can be compared with atmosphere models to infer the presence of particular atomic or molecular compounds in the atmosphere of WASP-48b. Results. After removing the transit model and systematic trends to the curves we reached precisions between 261 ppm and 455–755 ppm for the white and spectroscopic light curves, respectively. We obtained Rp/Rs uncertainty values between 0.8 × 10-3 and 1.5 × 10-3 for all the curves analyzed in this work. The measured transit depth for the curves made by integrating the wavelength range between 530 nm and 905 nm is in agreement with previous studies. We report a relatively flat transmission spectrum for WASP-48b with no statistical significant detection of atmospheric species, although the theoretical models that fit the data more closely include TiO and VO.
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Chandar, Rupali, Luciana Bianchi, Holland C. Ford, and Ata Sarajedini. "Kinematics of Star Clusters in M33: Distinct Populations." Symposium - International Astronomical Union 207 (2002): 160–62. http://dx.doi.org/10.1017/s0074180900223619.
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We analyse star cluster properties in the nearby spiral galaxy M33, combining our extensive HST WFPC2 photometry and ground-based follow up spectroscopy. These data show that cluster velocity dispersion increases with age. Simulations comparing synthetic disk and halo populations with observations indicate a composite disk/halo system for the old M33 clusters. The best fit fraction of 85 ± 5% halo plus 15 ± 5% disk differs from that found in the Milky Way, where ∼ 30% of the globular clusters are metal rich objects associated with the bulge and/or thick disk. Spectroscopic line indices for a halo subsample (17 objects) reveal an age spread of ∼ 5 — 7 Gyr, and little progression in metal abundance with age. This is consistent with a chaotic formation for a substantial portion of the M33 halo, and also consistent with an accretion origin for a large number of the halo clusters.
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Mikolajewski, M., T. Tomov, and J. Mikolajewska. "Optical Spectroscopy of CH Cygni in 1985/86." International Astronomical Union Colloquium 93 (1987): 733–45. http://dx.doi.org/10.1017/s0252921100105615.
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AbstractSome arguments for the explanation of the spectroscopic and photometric behavior of CH Cyg in terms of an eclipsing binary with P=5700 days, consisting of M6 III star and an accreting white dwarf, are presented. Physical and geometrical parameters of the system have been estimated and discussed.
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Stoyanov, K. A., K. Iłkiewicz, G. J. M. Luna, J. Mikołajewska, K. Mukai, J. Martí, G. Latev, S. Boeva, and R. K. Zamanov. "Optical spectroscopy and X-ray observations of the D-type symbiotic star EF Aql." Monthly Notices of the Royal Astronomical Society 495, no. 1 (May 13, 2020): 1461–67. http://dx.doi.org/10.1093/mnras/staa1310.
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ABSTRACT We performed high-resolution optical spectroscopy and X-ray observations of the recently identified Mira-type symbiotic star EF Aql. Based on high-resolution optical spectroscopy obtained with the Southern African Large Telescope (SALT), we determine the temperature (∼55 000 K) and the luminosity (∼5.3 L⊙) of the hot component in the system. The heliocentric radial velocities of the emission lines in the spectra reveal possible stratification of the chemical elements. We also estimate the mass-loss rate of the Mira donor star. Our Swift observation did not detect EF Aql in X-rays. The upper limit of the X-ray observations is 10−12 erg cm−2 s−1, which means that EF Aql is consistent with the faintest X-ray systems detected so far. Otherwise we detected it with the UltraViolet and Optical Telescope (UVOT) instrument with an average UVM2 magnitude of 14.05. During the exposure, EF Aql became approximately 0.2 UVM2 magnitudes fainter. The periodogram analysis of the V-band data reveals an improved period of 320.4 ± 0.3 d caused by the pulsations of the Mira-type donor star.
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Frémat, Y., P. Lampens, H. Hensberge, T. Arentoft, P. De Cat, R. Garrido, L. Parrao, J. H. Peña, P. Mathias, and P. Van Cauteren. "High resolution spectroscopy of the triple system 20 Leo." International Astronomical Union Colloquium 193 (2004): 395–98. http://dx.doi.org/10.1017/s0252921100011015.
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Abstract20 Leo is a spectroscopic triple system composed of 3 very similar stars, one of which seems to be aδSct star. Observations at high spectral and high time resolution have been obtained at the Observatoire de Haute Provence with the ELODIE spectrograph on the 1.9-m telescope. The spectra were taken during 7 nights in 2003 January and cover the whole optical domain from 3900 to 6800 Å. We used a Fourier transform technique recently developed by P. Hadrava to disentangle the combined spectrum. Application of the method allows the derivation of radial velocities at all orbital phases (even at phases of complete blending), as well as individual spectra for each component. From these computations we deduced more accurate individual radial velocities and improved orbital parameters describing the motion of the inner binary. Model atmospheres were used to analyze each individual spectrum and determine stellar fundamental parameters of the three components such as effective temperature, surface gravity and projected rotation velocity.
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Surace, C., J. Hecquet, and M. Auriere. "Spectroscopic Study of NGC 6119 - NGC 6120 System." Symposium - International Astronomical Union 171 (1996): 448. http://dx.doi.org/10.1017/s0074180900233664.
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NGC6119 and NGC6120 have been listed in Kiso catalog (Takase et al., 1987) as Sc and Irr galaxies. They have been selected by their clumpy features in order to investigate their nature and star formation history using slit spectroscopy. They have similar systemic velocities (respectively 9215 and 9200 km ·s–1) and seem to be members of a low gravitational interacting system of 4 galaxies (with MCG-6-36-30 and NGC6122).
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Piccioni, A., C. Bartolini, S. Bernabei, S. Galleti, A. Guarnieri, and G. Valentini. "Photometry and Spectroscopy of X Per During the Years 1996-1999." International Astronomical Union Colloquium 175 (2000): 585–88. http://dx.doi.org/10.1017/s0252921100056578.
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AbstractUBVRI photoelectric monitoring of the Be star X Per, a transient X-ray binary, during the last four years, along with some optical spectra are presented and briefly discussed in the context of the long term behaviour of the system.
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Bourrier, V., X. Dumusque, C. Dorn, G. W. Henry, N. Astudillo-Defru, J. Rey, B. Benneke, et al. "The 55 Cancri system reassessed." Astronomy & Astrophysics 619 (October 30, 2018): A1. http://dx.doi.org/10.1051/0004-6361/201833154.
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Orbiting a bright, nearby star the 55 Cnc system offers a rare opportunity to study a multiplanet system that has a wide range of planetary masses and orbital distances. Using two decades of photometry and spectroscopy data, we have measured the rotation of the host star and its solar-like magnetic cycle. Accounting for this cycle in our velocimetric analysis of the system allows us to revise the properties of the outermost giant planet and its four planetary companions. The innermost planet 55 Cnc e is an unusually close-in super-Earth, whose transits have allowed for detailed follow-up studies. Recent observations favor the presence of a substantial atmosphere yet its composition, and the nature of the planet, remain unknown. We combined our derived planet mass (Mp = 8.0 ± 0.3 MEarth) with refined measurement of its optical radius derived from HST/STIS observations (Rp = 1.88 ± 0.03 REarth over 530–750 nm) to revise the density of 55 Cnc e (ρ = 6.7 ± 0.4 g cm−3). Based on these revised properties we have characterized possible interiors of 55 Cnc e using a generalized Bayesian model. We confirm that the planet is likely surrounded by a heavyweight atmosphere, contributing a few percents of the planet radius. While we cannot exclude the presence of a water layer underneath the atmosphere, this scenario is unlikely given the observations of the planet across the entire spectrum and its strong irradiation. Follow-up observations of the system in photometry and in spectroscopy over different time-scales are needed to further investigate the nature and origin of this iconic super-Earth.
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Armas Padilla, M., T. Muñoz-Darias, F. Jiménez-Ibarra, J. A. Fernández-Ontiveros, J. Casares, M. A. P. Torres, J. García-Rojas, V. A. Cúneo, and N. Degenaar. "Optical spectroscopy of 4U 1812–12." Astronomy & Astrophysics 644 (December 2020): A63. http://dx.doi.org/10.1051/0004-6361/202038997.
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The persistent low-luminosity neutron star X-ray binary 4U 1812−12 is a potential member of the scarce family of ultra-compact systems. We performed deep photometric and spectroscopic optical observations with the 10.4 m Gran Telescopio Canarias in order to investigate the chemical composition of the accreted plasma, which is a proxy for the donor star class. We detect a faint optical counterpart (g ∼ 25, r ∼ 23) that is located in the background of the outskirts of the Sharpless 54 H II region, whose characteristic nebular lines superimpose on the X-ray binary spectrum. Once this is corrected for, the actual source spectrum lacks hydrogen spectral features. In particular, the Hα emission line is not detected, with an upper limit (3σ) on the equivalent width of < 1.3 Å. Helium (He I) lines are also not observed, even though our constraints are not restrictive enough to properly test the presence of this element. We also provide stringent upper limits on the presence of emission lines from other elements, such as C and O, which are typically found in ultra-compact systems with C−O white dwarfs donors. The absence of hydrogen features, the persistent nature of the source at low luminosity, and the low optical–to–X-ray flux ratio confirm 4U 1812−12 as a compelling ultra-compact X-ray binary candidate, for which we tentatively propose a He-rich donor based on the optical spectrum and the detection of short thermonuclear X-ray bursts. In this framework, we discuss the possible orbital period of the system according to disc instability and evolutionary models.
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Zieba, S., K. Zwintz, M. A. Kenworthy, and G. M. Kennedy. "Transiting exocomets detected in broadband light by TESS in the β Pictoris system." Astronomy & Astrophysics 625 (May 2019): L13. http://dx.doi.org/10.1051/0004-6361/201935552.
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Aims. We search for signs of falling evaporating bodies (FEBs, also known as exocomets) in photometric time series obtained for β Pictoris after fitting and removing its δ Scuti-type pulsation frequencies. Methods. Using photometric data obtained by the TESS satellite we determined the pulsational properties of the exoplanet host star β Pictoris through frequency analysis. We then pre-whitened the 54 identified δ Scuti p-modes and investigated the residual photometric time series for the presence of FEBs. Results. We identify three distinct dipping events in the light curve of β Pictoris over a 105-day period. These dips have depths from 0.5 to 2 millimagnitudes and durations of up to 2 days for the largest dip. These dips are asymmetric in nature and are consistent with a model of an evaporating comet with an extended tail crossing the disc of the star Conclusions. We present the first broadband detections of exocomets crossing the disc of β Pictoris, complementing the predictions made 20 years earlier by Lecavelier Des Etangs et al. (1999, A&A, 343, 916). No periodic transits are seen in this time series. These observations confirm the spectroscopic detection of exocomets in calcium H and K lines that have been seen in high resolution spectroscopy.
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Lennon, D. J., J. Maíz Apellániz, A. Irrgang, R. Bohlin, S. Deustua, P. L. Dufton, S. Simón-Díaz, et al. "Hubble spectroscopy of LB-1: Comparison with B+black-hole and Be+stripped-star models." Astronomy & Astrophysics 649 (May 2021): A167. http://dx.doi.org/10.1051/0004-6361/202040253.
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Context. LB-1 (alias ALS 8775) has been proposed as either an X-ray dim B-type star plus black hole (B+BH) binary or a Be star plus an inflated stripped star (Be+Bstr) binary. The latter hypothesis contingent upon the detection and characterization of the hidden broad-lined star in a composite optical spectrum. Aims. Our study is aimed at testing the published B+BH (single star) and Be+Bstr (binary star) models using a flux-calibrated UV-optical-IR spectrum. Methods. The Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope (HST) was used to obtain a flux-calibrated spectrum with an accuracy of ∼1%. We compared these data with non-local thermal equilibrium (non-LTE) spectral energy distributions (SED) and line profiles for the proposed models. The Hubble data, together with the Gaia EDR3 parallax and a well-determined extinction, were used to provide tight constraints on the properties and stellar luminosities of the LB-1 system. In the case of the Be+Bstr model we adopted the published flux ratio for the Be and Bstr stars, re-determined the Teff of the Bstr using the silicon ionization balance, and inferred Teff for the Be star from the fit to the SED. Results. The UV data strongly constrain the microturbulence velocity to ≲2 km s−1 for the stellar components of both models. We also find stellar parameters consistent with previous results, but with greater precision enabled by the Hubble SED. For the B+BH single-star model, we find the parameters (Teff, log(L/L⊙), Mspec/M⊙) of the B-type star to be (15 300 ± 300 K, 3.23−0.10+0.09, 5.2−1.4+1.8). For the Bstr star we obtain (12 500 ± 100 K, 2.70−0.09+0.09, 0.8−0.3+0.5), and for the Be star (18 900 ± 200 K, 3.04−0.09+0.09, 3.4−1.8+3.5). While the Be+Bstr model is a better fit to the He I lines and cores of the Balmer lines in the optical, the B+BH model provides a better fit to the Si IV resonance lines in the UV. The analysis also implies that the Bstr star has roughly twice the solar silicon abundance, which is difficult to reconcile with a stripped star origin. The Be star, on the other hand, has a rather low luminosity and a spectroscopic mass that is inconsistent with its possible dynamical mass. Conclusions. We provide tight constraints on the stellar luminosities of the Be+Bstr and B+BH models. For the former, the Bstr star appears to be silicon-rich, while the notional Be star appears to be sub-luminous for a classical Be star of its temperature and the predicted UV spectrum is inconsistent with the data. This latter issue can be significantly improved by reducing the Teff and radius of the Be star, at the cost, however, of a different mass ratio as a result. In the B+BH model, the single B-type spectrum is a good match to the UV spectrum. Adopting a mass ratio of 5.1 ± 0.1, from the literature, implies a BH mass of ∼21−8+9 M⊙.
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Echevarría, J., F. Diego, M. Tapia, and R. Costero. "Echelle-Mepsicron Time-Resolved Spectroscopy of the Dwarf Nova SS Cygni." International Astronomical Union Colloquium 93 (1987): 111. http://dx.doi.org/10.1017/s0252921100104701.
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AbstractHigh dispersion time-resolved spectrograms of the dwarf nova SS Cygni, obtained with the Echelle-Mepsicron system, show double peaked emission lines with a complex profile. The intensity of the Hβ line appears to be modulated by the orbital period. Radial velocity measurements of the wings of Hβ and of the absorption line system of the late-type star yield semiamplitude values of Kem = 101 ± 6 km s−1 and Kab = 151 ± 7 km s−1, respectively. Radial velocity measurements of the blue and red peaks and of the central absorption of Hβ reveal a synchronous movement with the broad wings, although there is some evidence of a narrow component probably associated with a hot spot in the disk or a chromospheric emission line from the secondary star. The Hβ modulation, the double profile and recently discovered UBV light variations support an inclination angle i ~ 50°. The masses of the primary and secondary stars using this angle and the observed semiamplitudes are Mp = 0.60 M⊙ and Ms = 0.40 M⊙, respectively. A detailed analysis of the absorption lines reveals a spectral type of K2V.
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Murgas, F., G. Chen, E. Pallé, L. Nortmann, and G. Nowak. "The GTC exoplanet transit spectroscopy survey." Astronomy & Astrophysics 622 (February 2019): A172. http://dx.doi.org/10.1051/0004-6361/201834063.
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Context. Rayleigh scattering in a hydrogen-dominated exoplanet atmosphere can be detected using ground- or space-based telescopes. However, stellar activity in the form of spots can mimic Rayleigh scattering in the observed transmission spectrum. Quantifying this phenomena is key to our correct interpretation of exoplanet atmospheric properties. Aims. We use the ten-meter Gran Telescopio Canarias (GTC) telescope to carry out a ground-based transmission spectra survey of extrasolar planets to characterize their atmospheres. In this paper we investigate the exoplanet HAT-P-11b, a Neptune-sized planet orbiting an active K-type star. Methods. We obtained long-slit optical spectroscopy of two transits of HAT-P-11b with the Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy (OSIRIS) on August 30, 2016 and September 25, 2017. We integrated the spectrum of HAT-P-11 and one reference star in several spectroscopic channels across the λ ~ 400–785 nm region, creating numerous light curves of the transits. We fit analytic transit curves to the data taking into account the systematic effects and red noise present in the time series in an effort to measure the change of the planet-to-star radius ratio (Rp∕Rs) across wavelength. Results. By fitting both transits together, we find a slope in the transmission spectrum showing an increase of the planetary radius towards blue wavelengths. Closer inspection of the transmission spectrum of the individual data sets reveals that the first transit presents this slope while the transmission spectrum of the second data set is flat. Additionally, we detect hints of Na absorption on the first night, but not on the second. We conclude that the transmission spectrum slope and Na absorption excess found in the first transit observation are caused by unocculted stellar spots. Modeling the contribution of unocculted spots to reproduce the results of the first night we find a spot filling factor of δ = 0.62−0.17+0.20 and a spot-to-photosphere temperature difference of ΔT = 429−299+184 K.
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Yuliana, Fitri, Zulkarnain Zulkarnain, and Hakim Luthfi Malasan. "PENENTUAN KOMPOSISI KIMIAWI ATMOSFER DAN TEMPERATUR EFEKTIF PADA BINTANG VEGA (α Lyr) DENGAN MENGGUNAKAN METODE SPEKTROSKOPI ABSORPSI." Komunikasi Fisika Indonesia 16, no. 2 (October 31, 2019): 96. http://dx.doi.org/10.31258/jkfi.16.2.96-102.
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The star spectrum is an information which is though to be a map of the star. The shape of the spectral line actually shows the nature of the star atmosphere, which is the only part researcher can be reached. The intensities of spectral lines will determine the chemical composition of the stars contained in the atmospheres of the stars. The approach used to determine the chemical composition and the effective temperature of the star is spectroscopy. The spectroscopy method had been done in this study using the GAO-ITB RTS telescope system which consisting of the Celestron C11 telescope, NEO-R 1000 spectrograph and CCD SBIG ST-8 camera. The object studied is Vega (α Lyr) star which has a magnitude of 0.00 that the main sequence star of the A0 spectrum class. The image data obtained then be processed using IRAF software to obtain the final spectrum graph with the y-axis representing the flux in erg cm-2s-1 and the x-axis representing the wavelength in units of Å. Furthermore, we match the absorption wavelength on the final spectrum graph to the existing wavelength of the Atomic Spectra Database (ASD) to identify the atmospheric chemical composition of the Vega star. Effective temperature can be calculated by using the Wien shifting laws by find out the maximum wavelength of the final spectrum graph. The most found element in the atmosphere of Vega star was hydrogen (H) that consist of Hε, Hδ, Hγ, Hβ, and Hα. The value of effective temperature of the Vega star is 7136 K that has difference percentage of 22.85 % from the mean temperature of A type star.
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Hareter, Markus, and Margit Paparó. "CoRoT target HD 51844: a δ Scuti star in a binary system with periastron brightening." Proceedings of the International Astronomical Union 9, S301 (August 2013): 59–62. http://dx.doi.org/10.1017/s1743921313014087.
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AbstractThe star HD 51844 was observed in the CoRoT LRa02 as a target in the seismology field, which turned out to be an SB2 system. The 117-day light curve revealed δ Scuti pulsations in the range of 6 to 15 d−1 where four frequencies have amplitudes larger than 1.4 mmag, and a rich frequency spectrum with amplitudes lower than 0.6 mmag. Additionally, the light curve exhibits a 3-mmag brightening event recurring every 33.5 days with a duration of about 5 days. The radial velocities from spectroscopy confirmed that the star is an eccentric binary system with nearly identical masses and physical parameters. The brightening event in the light curve coincides with the maximum radial-velocity separation showing that the brightening is in fact caused by tidal distortion and/or reflected light. One component displays large line-profile variations, while the other does not show significant variation. The frequency analysis revealed a quintuplet structure of the four highest-amplitude frequencies, which is due to the orbital motion of the pulsating star.
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Lane, Benjamin F., Matthew W. Muterspaugh, R. F. Griffin, C. D. Scarfe, Francis C. Fekel, Michael H. Williamson, Joel A. Eaton, M. Shao, M. M. Colavita, and Maciej Konacki. "THE ORBITS OF THE TRIPLE-STAR SYSTEM 1 GEMINORUM FROM PHASES DIFFERENTIAL ASTROMETRY AND SPECTROSCOPY." Astrophysical Journal 783, no. 1 (February 5, 2014): 3. http://dx.doi.org/10.1088/0004-637x/783/1/3.
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Holberg, J. B., S. L. Casewell, Howard E. Bond, M. R. Burleigh, and M. A. Barstow. "Hubble Space Telescope imaging and spectroscopy of the sirius-like triple star system HD 217411." Monthly Notices of the Royal Astronomical Society 444, no. 3 (September 2014): 2022–30. http://dx.doi.org/10.1093/mnras/stu1431.
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Kunovac Hodžić, Vedad, Amaury H. M. J. Triaud, David V. Martin, Daniel C. Fabrycky, Heather M. Cegla, Andrew Collier Cameron, Samuel Gill, et al. "The EBLM project – VII. Spin–orbit alignment for the circumbinary planet host EBLM J0608-59 A/TOI-1338 A." Monthly Notices of the Royal Astronomical Society 497, no. 2 (July 15, 2020): 1627–33. http://dx.doi.org/10.1093/mnras/staa2071.
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ABSTRACT A dozen short-period detached binaries are known to host transiting circumbinary planets. In all circumbinary systems so far, the planetary and binary orbits are aligned within a couple of degrees. However, the obliquity of the primary star, which is an important tracer of their formation, evolution, and tidal history, has only been measured in one circumbinary system until now. EBLM J0608-59/TOI-1338 is a low-mass eclipsing binary system with a recently discovered circumbinary planet identified by TESS. Here, we perform high-resolution spectroscopy during primary eclipse to measure the projected stellar obliquity of the primary component. The obliquity is low, and thus the primary star is aligned with the binary and planetary orbits with a projected spin–orbit angle β = 2${_{.}^{\circ}}$8 ± 17${_{.}^{\circ}}$1. The rotation period of 18.1 ± 1.6 d implied by our measurement of vsin i⋆ suggests that the primary has not yet pseudo-synchronized with the binary orbit, but is consistent with gyrochronology and weak tidal interaction with the binary companion. Our result, combined with the known coplanarity of the binary and planet orbits, is suggestive of formation from a single disc. Finally, we considered whether the spectrum of the faint secondary star could affect our measurements. We show through simulations that the effect is negligible for our system, but can lead to strong biases in vsin i⋆ and β for higher flux ratios. We encourage future studies in eclipse spectroscopy test the assumption of a dark secondary for flux ratios ≳1 ppt.
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Mennickent, Ronald E., Darek Graczyk, Zbigniew Kołaczkowski, Gabriela Michalska, Daniela Barría, and Ewa Niemczura. "Optical spectroscopy of DPVs and the case of LP Ara." Proceedings of the International Astronomical Union 6, S272 (July 2010): 527–28. http://dx.doi.org/10.1017/s1743921311011306.
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AbstractWe present preliminary results of our spectroscopic campaign of a group of intermediate mass interacting binaries dubbed “Double Periodic Variables” (DPVs), characterized by orbital light curves and additional long photometric cycles recurring roughly after 33 orbital periods (Mennickent et al. 2003, 2005). They have been interpreted as interacting, semi-detached binaries showing cycles of mass loss into the interstellar medium (Mennickent et al. 2008, Mennickent & Kołaczkowski 2009). High resolution Balmer and helium line profiles of DPVs can be interpreted in terms of mass flows in these systems. A system solution is given for LP Ara, based on modeling of the ASAS V-band orbital light curve and the radial velocity of the donor star.
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Drinkwater, M. J., J. B. Jones, M. D. Gregg, and S. Phillipps. "Compact Stellar Systems in the Fornax Cluster: Super-massive Star Clusters or Extremely Compact Dwarf Galaxies?" Publications of the Astronomical Society of Australia 17, no. 3 (2000): 227–33. http://dx.doi.org/10.1071/as00034.
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AbstractWe describe a population of compact objects in the centre of the Fornax Cluster which were discovered as part of our 2dF Fornax Spectroscopic Survey. These objects have spectra typical of old stellar systems, but are unresolved on photographic sky survey plates. They have absolute magnitudes −13 < MB < −11, so they are 10 times more luminous than any Galactic globular clusters, but fainter than any known compact dwarf galaxies. These objects are all within 30 arcminutes of the central galaxy of the cluster, NGC 1399, but are distributed over larger radii than the globular cluster system of that galaxy. We suggest that these objects are either super-massive star clusters (intra-cluster globular clusters or tidally stripped nuclei of dwarf galaxies) or a new type of low-luminosity, compact elliptical dwarf (‘M32-type”) galaxy. The best way to test these hypotheses will be to obtain high-resolution imaging and high-dispersion spectroscopy to determine their structures and mass-to-light ratios. This will allow us to compare them to known compact objects and establish whether they represent a new class of hitherto unknown stellar system.
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Pyun, Jeffrey, Ian Rees, Jean M. J. Fréchet, and Craig J. Hawker. "Evaluating the Effect of Termination by Chain - Chain Coupling in Living Free-Radical Polymerizations." Australian Journal of Chemistry 56, no. 8 (2003): 775. http://dx.doi.org/10.1071/ch03041.
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A novel approach based on the reaction of multifunctional star polymers with chromophore-labelled linear polymers is presented for evaluating the extent of termination by chain–chain coupling during living free-radical polymerizations. A mixed initiating system consisting of an unlabelled, multifunctional initiator and an excess of a monofunctional alkoxyamine initiator containing a chromophore, such as pyrene, is used to initiate the living polymerization of vinyl monomers leading to a mixture of star and linear polymers. The occurrence of chain–chain coupling is readily identified and quantified by isolating the star polymer that is obtained and elucidating the level of incorporation of pyrene units by UV/vis spectroscopy. This allows the level of chain–chain coupling to be determined since the inclusion of pyrene into the star structure is a direct result of termination by radical coupling.
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Yoshida, M., Y. Shimizu, H. Koyano, G. Kosugi, K. Aoki, H. Ohtani, T. Sasaki, and M. Sasaki. "Tridimensional Observations of Nearby Active Galaxies Using OAO Spectronebulagraph." International Astronomical Union Colloquium 149 (1995): 207–8. http://dx.doi.org/10.1017/s0252921100022971.
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We developed a slit-scanning type 3D-spectroscopic system named as Spectronebulagraph (hereafter SNG; Kosugi et al. 1994) at Okayama Astrophysical Observatory. A detailed description about SNG is presented by Ohtani et al. elsewhere in this colloquium. We present here the results of the 3D-spectroscopy of four nearby active galaxies by using SNG.This nearby (at distance of 5.4 Mpc) Magellanic irregular galaxy has many H II regions in its main body suggesting violent star-formation activity. We performed tridimensional observations of NGC 4449 using SNG in order to obtain detailed kinematic structure and then to investigate the star-formation mechanism of NGC 4449. Hα intensity map, Hα velocity field are shown in figure 1. As is obvious in lower panel of figure 1, no global rotational motion was detected. Most impressive feature of the velocity field is kpc-scale mosaic structure of low velocity and high velocity components. Also, many filamentary components were newly found in 3D-datacube of the SNG observation.
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Shenar, T., R. Hainich, H. Todt, A. F. J. Moffat, A. Sander, L. M. Oskinova, V. Ramachandran, et al. "The shortest-period Wolf-Rayet binary in the Small Magellanic Cloud: Part of a high-order multiple system." Astronomy & Astrophysics 616 (August 2018): A103. http://dx.doi.org/10.1051/0004-6361/201833006.
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Context. SMC AB 6 is the shortest-period (P = 6.5 d) Wolf-Rayet (WR) binary in the Small Magellanic Cloud. This binary is therefore a key system in the study of binary interaction and formation of WR stars at low metallicity. The WR component in AB 6 was previously found to be very luminous (log L = 6.3 [L⊙]) compared to its reported orbital mass (≈8 M⊙), placing it significantly above the Eddington limit. Aims. Through spectroscopy and orbital analysis of newly acquired optical data taken with the Ultraviolet and Visual Echelle Spectrograph (UVES), we aim to understand the peculiar results reported for this system and explore its evolutionary history. Methods. We measured radial velocities via cross-correlation and performed a spectral analysis using the Potsdam Wolf-Rayet model atmosphere code. The evolution of the system was analyzed using the Binary Population and Spectral Synthesis evolution code. Results. AB 6 contains at least four stars. The 6.5 d period WR binary comprises the WR primary (WN3:h, star A) and a rather rapidly rotating (veq = 265 km s−1) early O-type companion (O5.5 V, star B). Static N III and N IV emission lines and absorption signatures in He lines suggest the presence of an early-type emission line star (O5.5 I(f), star C). Finally, narrow absorption lines portraying a long-term radial velocity variation show the existence of a fourth star (O7.5 V, star D). Star D appears to form a second 140 d period binary together with a fifth stellar member, which is a B-type dwarf or a black hole. It is not clear that these additional components are bound to the WR binary. We derive a mass ratio of MO∕MWR = 2.2 ± 0.1. The WR star is found to be less luminous than previously thought (log L = 5.9 [L⊙]) and, adopting MO = 41 M⊙ for star B, more massive (MWR = 18 M⊙). Correspondingly, the WR star does not exceed the Eddington limit. We derive the initial masses of Mi,WR = 60 M⊙ and Mi,O = 40 M⊙ and an age of 3.9 Myr for the system. The WR binary likely experienced nonconservative mass transfer in the past supported by the relatively rapid rotation of star B. Conclusions. Our study shows that AB 6 is a multiple – probably quintuple – system. This finding resolves the previously reported puzzle of the WR primary exceeding the Eddington limit and suggests that the WR star exchanged mass with its companion in the past.
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Armas Padilla, M., and E. López-Navas. "On the ultra-compact nature of the neutron star system 1RXS J170854.4−321857: insights from X-ray spectroscopy." Monthly Notices of the Royal Astronomical Society 488, no. 4 (July 25, 2019): 5014–19. http://dx.doi.org/10.1093/mnras/stz2004.
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ABSTRACT The relatively small family of ultra-compact X-ray binary systems is of great interest for many areas of astrophysics. We report on a detailed X-ray spectral study of the persistent neutron star low-mass X-ray binary 1RXS J170854.4−321857. We analysed two XMM–Newton observations obtained in late 2004 and early 2005 when, in agreement with previous studies, the system displayed an X-ray luminosity (0.5–10 keV) of ${\sim} 1\times 10^{36}\, \mathrm{erg~s}^{-1}$. The spectrum can be described by a Comptonized emission component with Γ ∼ 1.9 and a distribution of seed photons with a temperature of ∼0.23 keV. A prominent residual feature is present at soft energies, which is reproduced by the absorption model if overabundances of Ne and Fe are allowed. We discuss how similar observables, which might be attributed to the peculiar (non-solar) composition of the plasma donated by the companion star, are a common feature in confirmed and candidate ultra-compact systems. Although this interpretation is still under debate, we conclude that the detection of these features along with the persistent nature of the source at such low luminosity and the intermediate–long burst that it displayed in the past confirms 1RXS J170854.4−321857 as a solid ultra-compact X-ray binary candidate.
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Palle, E., M. Oshagh, N. Casasayas-Barris, T. Hirano, M. Stangret, R. Luque, J. Strachan, et al. "Transmission spectroscopy and Rossiter-McLaughlin measurements of the young Neptune orbiting AU Mic." Astronomy & Astrophysics 643 (October 28, 2020): A25. http://dx.doi.org/10.1051/0004-6361/202038583.
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AU Mic b is a Neptune-sized planet on an 8.47-day orbit around the nearest pre-main sequence (~20 Myr) star to the Sun, the bright (V = 8.81) M dwarf AU Mic. The planet was preliminary detected in Doppler radial velocity time series and recently confirmed to be transiting with data from the TESS mission. AU Mic b is likely to be cooling and contracting and might be accompanied by a second, more massive planet, in an outer orbit. Here, we present the observations of the transit of AU Mic b using ESPRESSO on the Very Large Telescope. We obtained a high-resolution time series of spectra to measure the Rossiter-McLaughlin effect, to constrain the spin-orbit alignment of the star and planet, and to simultaneously attempt to retrieve the planet’s atmospheric transmission spectrum. These observations allowed us to study, for the first time, the early phases of the dynamical evolution of young systems. We applied different methodologies to derive the spin-orbit angle of AU Mic b, and all of them retrieve values consistent with the planet being aligned with the rotation plane of the star. We determined a conservative spin-orbit angle λ value of −2.96−10.30+10.44 degrees, indicative that the formation and migration of the planets of the AU Mic system occurred within the disc. Unfortunately, and despite the large signal-to-noise ratio of our measurements, the degree of stellar activity prevented us from detecting any features from the planetary atmosphere. In fact, our results suggest that transmission spectroscopy for recently formed planets around active young stars is going to remain very challenging, if at all possible, for the near future.
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Mengel, Sabine, Niranjan Thatte, Matthew Lehnert, and Reinhard Genzel. "Star Formation in NGC 4038/4039." Symposium - International Astronomical Union 205 (2001): 206–7. http://dx.doi.org/10.1017/s0074180900220986.
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We performed near infrared integral field spectroscopy of several star clusters and the nuclei of the prototypical merger NGC 4038/39 (“The Antennae”). Near infrared (NIR) images covered both galaxies. The collision of the two gas-rich spiral galaxies has triggered a starburst obvious from a large number of young star clusters. ISO data suggest that the most active star formation occurs in the region where the two galaxy disks overlap. A significant fraction of the total bolometric luminosity of the system is produced there. Since this region is heavily extincted in the optical, the investigation was made in the NIR. Using Brγ emission and CO absorption features as age indicators, we derive the ages and mass estimates of the star clusters from a comparison with stellar synthesis models. Extinction is calculated from the Brγ/Hα ratio. The young, bright star clusters have ages ranging from 4-12 Myrs, while the nuclear starbursts are much older (50-80 Myrs). The overlap region hosts most of the youngest star clusters below ∼8 Myrs, while the northwestern region is dominated by star clusters in the age range between 8 and 12 Myrs. Several regions, including the northern nucleus, show evidence for sequential star formation on small spatial scales (< 100pc).
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Ciocan, B. I., B. L. Ziegler, M. Verdugo, P. Papaderos, K. Fogarty, M. Donahue, and M. Postman. "The VLT-MUSE and ALMA view of the MACS 1931.8-2635 brightest cluster galaxy." Astronomy & Astrophysics 649 (May 2021): A23. http://dx.doi.org/10.1051/0004-6361/202040010.
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We reveal the importance of ongoing in situ star formation in the brightest cluster galaxy (BCG) in the massive cool-core CLASH cluster MACS 1931.8-2635 at a redshift of z = 0.35 by analysing archival VLT-MUSE optical integral field spectroscopy. Using a multi-wavelength approach, we assessed the stellar and warm ionised medium components, which were spatially resolved by the VLT-MUSE spectroscopy, and linked them to the molecular gas by incorporating sub-mm ALMA observations. We measured the fluxes of strong emission lines such as: [O II] λ3727, Hβ, [O III] λ5007, Hα, [N II] λ 6584, and [S II] λ6718, 6732, which allowed us to determine the physical conditions of the warm ionised gas, such as electron temperature, electron density, extinction, ionisation parameter, (O/H) gas metallicities, star formation rates, and gas kinematics, as well as the star formation history of the system. Our analysis reveals the ionising sources in different regions of the galaxy. The ionised gas flux brightness peak corresponds to the location of the supermassive black hole in the BCG and the system shows a diffuse warm ionised gas tail extending 30 kpc in the north-east direction. The ionised and molecular gas are co-spatial and co-moving, with the gaseous component in the tail likely falling inward, providing fuel for star formation and accretion-powered nuclear activity. The gas is ionised by a mix of star formation and other energetic processes which give rise to LINER-like emission, with active galactic nuclei emission dominant only in the BCG core. We measured a star formation rate of ∼97 M⊙ yr−1, with its peak at the BCG core. However, star formation accounts for only 50–60% of the energetics needed to ionise the warm gas. The stellar mass growth of the BCG at z < 0.5 is dominated either by in situ star formation generated by thermally unstable intracluster medium cooling or by dry mergers, with these mechanisms accounting for the build-up of 20% of the stellar mass of the system. Our measurements reveal that the most central regions of the BCG contain the lowest gas-phase oxygen abundance, whereas the Hα arm exhibits slightly more elevated values, suggesting the transport of gas out to large distances from the centre as a result of active galactic nuclei outbursts. The galaxy is a dispersion-dominated system that is typical for massive, elliptical galaxies. The gas and stellar kinematics are decoupled, with the gaseous velocity fields being more closely related to the bulk motions of the intracluster medium.
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Kerzendorf, Wolfgang E. "Type Ia Progenitor Hunt in Ancient Remnants." Proceedings of the International Astronomical Union 7, S281 (July 2011): 326–30. http://dx.doi.org/10.1017/s174392131201530x.
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AbstractThere is broad agreement that the stars which explode as Type Ia supernovae are white dwarfs. They have accreted material in a binary system until they are near the Chandrasekhar mass and detonate/deflagrate. The two main scenarios for this accretion process are merging with a companion white dwarf (double degenerate scenario), or accretion from a main-sequence to red giant donor (single degenerate scenario). The donor star survives post-explosion and would provide substantial evidence for the single degenerate scenario, if found. Our team is analyzing stars in close proximity to Galactic Type Ia remnants to find surviving donor stars. In my talk I will introduce the different progenitor systems and the expected state for a donor star today. I will outline our search using high resolution spectroscopy and will present updated results.
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Hoeijmakers, H. J., H. Schwarz, I. A. G. Snellen, R. J. de Kok, M. Bonnefoy, G. Chauvin, A. M. Lagrange, and J. H. Girard. "Medium-resolution integral-field spectroscopy for high-contrast exoplanet imaging." Astronomy & Astrophysics 617 (September 2018): A144. http://dx.doi.org/10.1051/0004-6361/201832902.
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Context. Angular differential imaging (ADI) and spectral differential imaging (SDI) are well-established high-contrast imaging techniques, but their application is challenging for companions at small angular separations from their host stars. Aims. The aim of this paper is to investigate to what extent adaptive-optics assisted, medium-resolution (R ~ 5000) integral field spectrographs (IFS) can be used to directly detect the absorption of molecular species in the spectra of planets and substellar companions when these are not present in the spectrum of the star. Methods. We analysed archival data of the β Pictoris system taken with the SINFONI integral field spectrograph located at ESO’s Very Large Telescope, originally taken to image β Pictoris b using ADI techniques. At each spatial position in the field, a scaled instance of the stellar spectrum is subtracted from the data after which the residuals are cross-correlated with model spectra. The cross-correlation co-adds the individual absorption lines of the planet emission spectrum constructively, while this is not the case for (residual) telluric and stellar features. Results. Cross-correlation with CO and H2O models results in significant detections of β Pictoris b with signal-to-noise ratios (S/Ns) of 13.7 and 16.4 respectively. Correlation with a T = 1700 K BT-Settl model provides a detection with an S/N of 22.8. This in contrast to application of ADI, which barely reveals the planet. While the adaptive optics system only achieved modest Strehl ratios of 19–27% leading to a raw contrast of 1:240 at the planet position, cross-correlation achieves a 3σ contrast limit of 2.7 × 10−5 in this 2.5 hr data set, a factor ~40 below the raw noise level at an angular distance of 0.36′′ from the star. Conclusions. Adaptive-optics assisted, medium-resolution IFS, such as SINFONI on the VLT and OSIRIS on the Keck Telescope, can be used for high-contrast imaging utilizing cross-correlation techniques for planets that are close to their star and embedded in speckle noise. We refer to this method as molecule mapping, and advocate its application to observations with future medium resolution instruments, in particular ERIS on the VLT, HARMONI on the ELT and NIRSpec, and MIRI on the JWST.
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Murphy, Simon J., Tanda Li, Sanjay Sekaran, Timothy R. Bedding, Jie Yu, Andrew Tkachenko, Isabel Colman, et al. "A binary with a δ Scuti star and an oscillating red giant: orbit and asteroseismology of KIC 9773821." Monthly Notices of the Royal Astronomical Society 505, no. 2 (May 24, 2021): 2336–48. http://dx.doi.org/10.1093/mnras/stab1436.
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ABSTRACT We study the δ Scuti – red giant (RG) binary KIC 9773821, the first double-pulsator binary of its kind. It was observed by Kepler during its 4-yr mission. Our aims are to ascertain whether the system is bound, rather than a chance alignment, and to identify the evolutionary state of the RG via asteroseismology. An extension of these aims is to determine a dynamical mass and an age prior for a δ Sct star, which may permit mode identification via further asteroseismic modelling. We determine spectroscopic parameters and radial velocities (RVs) for the RG component using HERMES@Mercator spectroscopy. Light arrival-time delays from the δ Sct pulsations are used with the red-giant RVs to determine that the system is bound and to infer its orbital parameters, including the binary mass ratio. We use asteroseismology to model the individual frequencies of the red giant to give a mass of $2.10^{+0.20}_{-0.10}$ M⊙ and an age of $1.08^{+0.06}_{-0.24}$ Gyr. We find that it is a helium-burning secondary clump star, confirm that it follows the standard $\nu _{\rm max}$ scaling relation, and confirm its observed period spacings match their theoretical counterparts in the modelling code mesa. Our results also constrain the mass and age of the δ Sct star. We leverage these constraints to construct δ Sct models in a reduced parameter space and identify four of its five pulsation modes.
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Shahbaz, T., M. Linares, P. Rodríguez-Gil, and J. Casares. "The binary millisecond pulsar PSR J1023+0038 – II. Optical spectroscopy." Monthly Notices of the Royal Astronomical Society 488, no. 1 (June 13, 2019): 198–212. http://dx.doi.org/10.1093/mnras/stz1652.
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ABSTRACT We present time-resolved optical spectroscopy of the ‘redback’ binary millisecond pulsar system PSR J1023+0038 during both its radio pulsar (2009) and accretion disc states (2014 and 2016). We provide observational evidence for the companion star being heated during the disc state. We observe a spectral type change along the orbit, from ∼G5 to ∼F6 at the secondary star’s superior and inferior conjunction, respectively, and find that the corresponding irradiating luminosity can be powered by the high-energy accretion luminosity or the spin-down luminosity of the neutron star. We determine the secondary star’s radial velocity semi-amplitude from the metallic (primarily Fe and Ca) and Hα absorption lines during these different states. The metallic and Hα radial velocity semi-amplitude determined from the 2009 pulsar-state observations allows us to constrain the secondary star’s true radial velocity K2 = 276.3 ± 5.6 km s−1 and the binary mass ratio q = 0.137 ± 0.003. By comparing the observed metallic and Hα absorption-line radial velocity semi-amplitudes with model predictions, we can explain the observed semi-amplitude changes during the pulsar state and during the pulsar/disc-state transition as being due to different amounts of heating and the presence of an accretion disc, respectively.
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Karl, Martina, Oliver Pfuhl, Frank Eisenhauer, Reinhard Genzel, Rebekka Grellmann, Maryam Habibi, Roberto Abuter, et al. "Multiple star systems in the Orion nebula." Astronomy & Astrophysics 620 (December 2018): A116. http://dx.doi.org/10.1051/0004-6361/201833575.
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This work presents an interferometric study of the massive-binary fraction in the Orion Trapezium cluster with the recently comissioned GRAVITY instrument. We observed a total of 16 stars of mainly OB spectral type. We find three previously unknown companions for θ1 Ori B, θ2 Ori B, and θ2 Ori C. We determined a separation for the previously suspected companion of NU Ori. We confirm four companions for θ1 Ori A, θ1 Ori C, θ1 Ori D, and θ2 Ori A, all with substantially improved astrometry and photometric mass estimates. We refined the orbit of the eccentric high-mass binary θ1 Ori C and we are able to derive a new orbit for θ1 Ori D. We find a system mass of 21.7 M⊙ and a period of 53 days. Together with other previously detected companions seen in spectroscopy or direct imaging, eleven of the 16 high-mass stars are multiple systems. We obtain a total number of 22 companions with separations up to 600 AU. The companion fraction of the early B and O stars in our sample is about two, significantly higher than in earlier studies of mostly OB associations. The separation distribution hints toward a bimodality. Such a bimodality has been previously found in A stars, but rarely in OB binaries, which up to this point have been assumed to be mostly compact with a tail of wider companions. We also do not find a substantial population of equal-mass binaries. The observed distribution of mass ratios declines steeply with mass, and like the direct star counts, indicates that our companions follow a standard power law initial mass function. Again, this is in contrast to earlier findings of flat mass ratio distributions in OB associations. We excluded collision as a dominant formation mechanism but find no clear preference for core accretion or competitive accretion.
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Stencel, Robert E. "Evidence for a Precessing Disk in the Extreme Binary ϵ Aurigae." Proceedings of the International Astronomical Union 2, S240 (August 2006): 202–4. http://dx.doi.org/10.1017/s1743921307004024.
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AbstractAmong the longest known eclipse durations and binary periods is that of the star ϵ Aurigae, which exhibits 2-year long eclipses every 27.1 years. Oddly, the nature of the secondary in the system continues to elude ready identification. In 1965, Huang proposed a massive disk as the eclipsing body, and study of the 1984 eclipse led Lissauer and Backman to suggest an embedded B star binary in the disk to maintain it. A collaboration of observers allows me to present recent optical photometry and spectroscopy, near-IR spectroscopy and Spitzer space telescope IRS and MIPS observations of ϵ Aurigae as it approaches its next eclipse. These data argue for current detectability of the embedded binary, and precession of the disk axis, suggesting a radical change is possible for the next mid-eclipse brightening. An international monitoring campaign for the 2009-2011 is being organized, and participation invited via website http://www.du.edu/~rstencel/epsaur.htm.
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Mason, Brian D., William I. Hartkopf, Dimitri Pourbaix, Colin D. Scarfe, Marion Schmitz, and Andrei A. Tokovinin. "DIVISION IV / COMMISSION 26 / WORKING GROUP BINARY AND MULTIPLE SYSTEM NOMENCLATURE." Proceedings of the International Astronomical Union 4, T27A (December 2008): 207–8. http://dx.doi.org/10.1017/s1743921308025520.
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The Working Group on Binary and Multiple System Nomenclature was formed within Commission 26 following Special Session 3 held during the 2003 Sydney General Assembly. Its purpose is to create the Washington Multiplicity Catalog, a comprehensive database first introduced at a multi-commission meeting at the IAU XXIV General Assembly in Manchester, 2000. Data are being compiled from the US Naval Observatory visual binary catalogs and supplemented with binary and multiple star information from other sources to include but not limited to spectroscopy, photometry, eclipsing and interacting system, as well as extra-solar planets and substellar companions. The goal being creation of a comprehensive hierarchical database and to reduce confusion from multiple nomenclature schemes used by disparate techniques.
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Maíz Apellániz, J., E. Trigueros Páez, I. Negueruela, R. H. Barbá, S. Simón-Díaz, J. Lorenzo, A. Sota, et al. "MONOS: Multiplicity Of Northern O-type Spectroscopic systems." Astronomy & Astrophysics 626 (June 2019): A20. http://dx.doi.org/10.1051/0004-6361/201935359.
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Context. Multiplicity in massive stars is key to understanding the chemical and dynamical evolution of galaxies. Among massive stars, those of O type play a crucial role due to their high masses and short lifetimes. Aims. MONOS (Multiplicity Of Northern O-type Spectroscopic systems) is a project designed to collect information and study O-type spectroscopic binaries with δ > −20°. In this first paper we describe the sample and provide spectral classifications and additional information for objects with previous spectroscopic and/or eclipsing binary orbits. In future papers we will test the validity of previous solutions and calculate new spectroscopic orbits. Methods. The spectra in this paper have two sources: the Galactic O-Star Spectroscopic Survey (GOSSS), a project that obtains blue-violet R ∼ 2500 spectroscopy of thousands of massive stars, and LiLiMaRlin, a library of libraries of high-resolution spectroscopy of massive stars obtained from four different surveys (CAFÉ-BEANS, OWN, IACOB, and NoMaDS) and additional data from our own observing programs and public archives. We have also used lucky images obtained with AstraLux. Results. We present homogeneous spectral classifications for 92 O-type spectroscopic multiple systems and ten optical companions, many of them original. We discuss the visual multiplicity of each system with the support of AstraLux images and additional sources. For eleven O-type objects and for six B-type objects we present their first GOSSS spectral classifications. For two known eclipsing binaries we detect double absorption lines (SB2) or a single moving line (SB1) for the first time, to which we add a third system reported by us recently. For two previous SB1 systems we detect their SB2 nature for the first time and give their first separate spectral classifications, something we have also done for a third object just recently identified as a SB2. We also detect nine new astrometric companions and provide updated information on several others. We emphasize the results for two stars: for σ Ori AaAbB we provide spectral classifications for the three components with a single observation for the first time thanks to a lucky spectroscopy observation obtained close to the Aa,Ab periastron and for θ1 Ori CaCb we add it to the class of Galactic Of?p stars, raising the number of its members to six. Our sample of O-type spectroscopic binaries contains more triple- or higher-order systems than double systems.