Journal articles on the topic 'Gravitational-wave Optical Transient Observer'
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1
Steeghs, D., D. K. Galloway, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, R. Cutter, et al. "The Gravitational-wave Optical Transient Observer (GOTO): prototype performance and prospects for transient science." Monthly Notices of the Royal Astronomical Society 511, no. 2 (January 12, 2022): 2405–22. http://dx.doi.org/10.1093/mnras/stac013.
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ABSTRACT The Gravitational-wave Optical Transient Observer (GOTO) is an array of wide-field optical telescopes, designed to exploit new discoveries from the next generation of gravitational wave detectors (LIGO, Virgo, and KAGRA), study rapidly evolving transients, and exploit multimessenger opportunities arising from neutrino and very high energy gamma-ray triggers. In addition to a rapid response mode, the array will also perform a sensitive, all-sky transient survey with few day cadence. The facility features a novel, modular design with multiple 40-cm wide-field reflectors on a single mount. In 2017 June, the GOTO collaboration deployed the initial project prototype, with 4 telescope units, at the Roque de los Muchachos Observatory (ORM), La Palma, Canary Islands. Here, we describe the deployment, commissioning, and performance of the prototype hardware, and discuss the impact of these findings on the final GOTO design. We also offer an initial assessment of the science prospects for the full GOTO facility that employs 32 telescope units across two sites.
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Mong, Y.-L., K. Ackley, D. K. Galloway, M. Dyer, R. Cutter, M. J. I. Brown, J. Lyman, et al. "Searching for Fermi GRB optical counterparts with the prototype Gravitational-wave Optical Transient Observer (GOTO)." Monthly Notices of the Royal Astronomical Society 507, no. 4 (September 7, 2021): 5463–76. http://dx.doi.org/10.1093/mnras/stab2499.
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ABSTRACT The typical detection rate of ∼1 gamma-ray burst (GRB) per day by the Fermi Gamma-ray Burst Monitor (GBM) provides a valuable opportunity to further our understanding of GRB physics. However, the large uncertainty of the Fermi localization typically prevents rapid identification of multiwavelength counterparts. We report the follow-up of 93 Fermi GRBs with the Gravitational-wave Optical Transient Observer (GOTO) prototype on La Palma. We selected 53 events (based on favourable observing conditions) for detailed analysis, and to demonstrate our strategy of searching for optical counterparts. We apply a filtering process consisting of both automated and manual steps to 60 085 candidates initially, rejecting all but 29, arising from 15 events. With ≈3 GRB afterglows expected to be detectable with GOTO from our sample, most of the candidates are unlikely to be related to the GRBs. Since we did not have multiple observations for those candidates, we cannot confidently confirm the association between the transients and the GRBs. Our results show that GOTO can effectively search for GRB optical counterparts thanks to its large field of view of ≈40 deg2 and its depth of ≈20 mag. We also detail several methods to improve our overall performance for future follow-up programmes of Fermi GRBs.
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Gompertz, B. P., R. Cutter, D. Steeghs, D. K. Galloway, J. Lyman, K. Ulaczyk, M. J. Dyer, et al. "Searching for electromagnetic counterparts to gravitational-wave merger events with the prototype Gravitational-Wave Optical Transient Observer (GOTO-4)." Monthly Notices of the Royal Astronomical Society 497, no. 1 (July 3, 2020): 726–38. http://dx.doi.org/10.1093/mnras/staa1845.
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ABSTRACT We report the results of optical follow-up observations of 29 gravitational-wave (GW) triggers during the first half of the LIGO–Virgo Collaboration (LVC) O3 run with the Gravitational-wave Optical Transient Observer (GOTO) in its prototype 4-telescope configuration (GOTO-4). While no viable electromagnetic (EM) counterpart candidate was identified, we estimate our 3D (volumetric) coverage using test light curves of on- and off-axis gamma-ray bursts and kilonovae. In cases where the source region was observable immediately, GOTO-4 was able to respond to a GW alert in less than a minute. The average time of first observation was 8.79 h after receiving an alert (9.90 h after trigger). A mean of 732.3 square degrees were tiled per event, representing on average 45.3 per cent of the LVC probability map, or 70.3 per cent of the observable probability. This coverage will further improve as the facility scales up alongside the localization performance of the evolving GW detector network. Even in its 4-telescope prototype configuration, GOTO is capable of detecting AT2017gfo-like kilonovae beyond 200 Mpc in favourable observing conditions. We cannot currently place meaningful EM limits on the population of distant ($\hat{D}_L = 1.3$ Gpc) binary black hole mergers because our test models are too faint to recover at this distance. However, as GOTO is upgraded towards its full 32-telescope, 2 node (La Palma & Australia) configuration, it is expected to be sufficiently sensitive to cover the predicted O4 binary neutron star merger volume, and will be able to respond to both northern and southern triggers.
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Hu, Y. D., X. Y. Li, A. J. Castro-Tirado, E. J. Fernandez-García, A. Castellon, I. Carrasco-García, C. Perez del Pulgar, et al. "THE BOOTES NETWORK IN THE GRAVITATIONAL WAVE ERA." Revista Mexicana de Astronomía y Astrofísica Serie de Conferencias 53 (September 1, 2021): 75–82. http://dx.doi.org/10.22201/ia.14052059p.2021.53.18.
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The Burst Optical Observer and Transient Exploring System (BOOTES) is a world-wide automatic telescope network which aims to repaid follow-up of transient and astrophysical sources in the sky for which the first station was installed in 1998. With the advent in 2015 of the LIGO/Virgo interferometers, as part of the new generation of detectors designed for the detection of the signal of gravitational waves, a new window to explore the Universe has been opened. Here we present the status of the BOOTES network, the related strategies regarding the follow-up of gravitational wave events and the developments in the Gravitational Wave Era. Some preliminary results regarding the BOOTES follow-up observations are presented.
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de Wet, S., P. J. Groot, S. Bloemen, R. Le Poole, M. Klein-Wolt, E. Körding, V. McBride, et al. "GW190814 follow-up with the optical telescope MeerLICHT." Astronomy & Astrophysics 649 (May 2021): A72. http://dx.doi.org/10.1051/0004-6361/202040231.
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Context. The Advanced LIGO and Virgo gravitational wave observatories detected a signal on 2019 August 14 during their third observing run, named GW190814. A large number of electromagnetic facilities conducted follow-up campaigns in the search for a possible counterpart to the gravitational wave event, which was made especially promising given the early source classification of a neutron star-black hole merger. Aims. We present the results of the GW follow-up campaign taken with the wide-field optical telescope MeerLICHT, located at the South African Astronomical Observatory Sutherland site. We use our results to constrain possible kilonova models. Methods. The MeerLICHT telescope observed more than 95% of the probability localisation each night for over a week in three optical bands (u, q, i) with our initial observations beginning almost two hours after the GW detection. We describe the search for new transients in MeerLICHT data and investigate how our limiting magnitudes can be used to constrain an AT2017gfo-like kilonova. Results. A single new transient was found in our analysis of MeerLICHT data, which we exclude from being the electromagnetic counterpart to GW190814 owing to the existence of a spatially unresolved source at the coordinates of the transient in archival data. Using our limiting magnitudes, the confidence with which we can exclude the presence of an AT2017gfo-like kilonova at the distance of GW190814 was low (< 10−4).
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van Roestel, J., P. J. Groot, T. Kupfer, K. Verbeek, S. van Velzen, M. Bours, P. Nugent, et al. "The Palomar Transient Factory Sky2Night programme." Monthly Notices of the Royal Astronomical Society 484, no. 4 (January 28, 2019): 4507–28. http://dx.doi.org/10.1093/mnras/stz241.
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Abstract We present results of the Sky2Night project: a systematic, unbiased search for fast optical transients with the Palomar Transient Factory. We have observed 407deg2 in R-band for eight nights at a cadence of 2 h. During the entire duration of the project, the 4.2 m William Herschel Telescope on La Palma was dedicated to obtaining identification spectra for the detected transients. During the search, we found 12 supernovae, 10 outbursting cataclysmic variables, nine flaring M-stars, three flaring active galactic nuclei, and no extragalactic fast optical transients. Using this systematic survey for transients, we have calculated robust observed rates for the detected types of transients, and upper limits of the rate of extragalactic fast optical transients of $\mathcal {R}\lt 37\times 10^{-4}$deg−2 d−1 and $\mathcal {R}\lt 9.3\times 10^{-4}$deg−2 d−1 for time-scales of 4 h and 1 d and a limiting magnitude of R ≈ 19.7. We use the results of this project to determine what kind of and how many astrophysical false positives we can expect when following up gravitational wave detections in search for kilonovae.
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Mong, Y.-L., K. Ackley, D. K. Galloway, T. Killestein, J. Lyman, D. Steeghs, V. Dhillon, et al. "Machine learning for transient recognition in difference imaging with minimum sampling effort." Monthly Notices of the Royal Astronomical Society 499, no. 4 (October 9, 2020): 6009–17. http://dx.doi.org/10.1093/mnras/staa3096.
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ABSTRACT The amount of observational data produced by time-domain astronomy is exponentially increasing. Human inspection alone is not an effective way to identify genuine transients from the data. An automatic real-bogus classifier is needed and machine learning techniques are commonly used to achieve this goal. Building a training set with a sufficiently large number of verified transients is challenging, due to the requirement of human verification. We present an approach for creating a training set by using all detections in the science images to be the sample of real detections and all detections in the difference images, which are generated by the process of difference imaging to detect transients, to be the samples of bogus detections. This strategy effectively minimizes the labour involved in the data labelling for supervised machine learning methods. We demonstrate the utility of the training set by using it to train several classifiers utilizing as the feature representation the normalized pixel values in 21 × 21 pixel stamps centred at the detection position, observed with the Gravitational-wave Optical Transient Observer (GOTO) prototype. The real-bogus classifier trained with this strategy can provide up to $95{{\ \rm per\ cent}}$ prediction accuracy on the real detections at a false alarm rate of $1{{\ \rm per\ cent}}$.
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Macri, Lucas M., Mario C. Díaz, and Diego Garcia Lambas. "Observations of the first electromagnetic counterpart to a gravitational wave source by the TOROS collaboration." Proceedings of the International Astronomical Union 13, S338 (October 2017): 80–83. http://dx.doi.org/10.1017/s1743921318003630.
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AbstractWe present the results of prompt optical follow-up of the electromagnetic counterpart of GW170817 by the Transient Optical Robotic Observatory of the South Collaboration (TOROS). We detected highly significant dimming in the light curves of the counterpart over the course of only 80 minutes of observations obtained ~35 hr after the trigger with the T80-South telescope. A second epoch of observations, obtained ~59 hr after the event with the EABA 1.5m telescope, confirms the fast fading nature of the transient. The observed colors of the counterpart suggest that this event was a “blue kilonova” relatively free of lanthanides.
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Almualla, Mouza, Michael W. Coughlin, Shreya Anand, Khalid Alqassimi, Nidhal Guessoum, and Leo P. Singer. "Dynamic scheduling: target of opportunity observations of gravitational wave events." Monthly Notices of the Royal Astronomical Society 495, no. 4 (June 1, 2020): 4366–71. http://dx.doi.org/10.1093/mnras/staa1498.
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ABSTRACT The simultaneous detection of electromagnetic and gravitational waves from the coalescence of two neutron stars (GW170817 and GRB170817A) has ushered in a new era of ‘multimessenger’ astronomy, with electromagnetic detections spanning from gamma to radio. This great opportunity for new scientific investigations raises the issue of how the available multimessenger tools can best be integrated to constitute a powerful method to study the transient Universe in particular. To facilitate the classification of possible optical counterparts to gravitational wave events, it is important to optimize the scheduling of observations and the filtering of transients, both key elements of the follow-up process. In this work, we describe the existing workflow whereby telescope networks such as GRANDMA and GROWTH are currently scheduled; we then present modifications we have developed for the scheduling process specifically, so as to face the relevant challenges that have appeared during the latest observing run of Advanced LIGO and Advanced Virgo. We address issues with scheduling more than one epoch for multiple fields within a skymap, especially for large and disjointed localizations. This is done in two ways: by optimizing the maximum number of fields that can be scheduled and by splitting up the lobes within the skymap by right ascension to be scheduled individually. In addition, we implement the ability to take previously observed fields into consideration when rescheduling. We show the improvements that these modifications produce in making the search for optical counterparts more efficient, and we point to areas needing further improvement.
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Becerra, R. L., S. Dichiara, A. M. Watson, E. Troja, N. R. Butler, M. Pereyra, E. Moreno Méndez, et al. "DDOTI observations of gravitational-wave sources discovered in O3." Monthly Notices of the Royal Astronomical Society 507, no. 1 (July 21, 2021): 1401–20. http://dx.doi.org/10.1093/mnras/stab2086.
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ABSTRACT We present optical follow-up observations with the Deca-Degree Optical Transient Imager (DDOTI) telescope of gravitational-wave (GW) events detected during the Advanced LIGO and Advanced Virgo O3 observing run. DDOTI is capable of responding to an alert in a few minutes, has an instantaneous field of about 69 deg2, and obtains 10σ upper limits of wlim = 18.5–20.5 AB mag in 1000 s of exposure, depending on the conditions. We observed 54 per cent (26 out of 48) of the unretracted GW alerts and did not find any electromagnetic counterparts. We compare our upper limits to various possible counterparts: the kilonova AT 2017gfo, models of radioactive- and magnetar-powered kilonovae, short gamma-ray burst afterglows, and active galactic nucleus (AGN) flares. Although the large positional uncertainties of GW sources do not allow us to place strong constraints during O3, DDOTI observations of well-localized GW events in O4 and beyond could meaningfully constrain models of compact binary mergers. We show that DDOTI is able to detect kilonovae similar to AT 2017gfo up to about 200 Mpc and magnetar-powered kilonovae up to 1 Gpc. We calculate that nearby (≲200 Mpc) afterglows have a high chance (≈70 per cent) to be detected by rapid (≲3 h) DDOTI observations if observed on-axis, whereas off-axis afterglows are unlikely to be seen. Finally, we suggest that long-term monitoring of massive BBH events with DDOTI could confirm or rule out late AGN flares associated with these events.
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Coward, D. M., M. Todd, T. P. Vaalsta, M. Laas-Bourez, A. Klotz, A. Imerito, L. Yan, et al. "The Zadko Telescope: A Southern Hemisphere Telescope for Optical Transient Searches, Multi-Messenger Astronomy and Education." Publications of the Astronomical Society of Australia 27, no. 3 (2010): 331–39. http://dx.doi.org/10.1071/as09078.
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AbstractThe new 1 m f/4 fast-slew Zadko Telescope was installed in June 2008 about 70 km north of Perth, Western Australia. It is the only metre-class optical facility at this southern latitude between the east coast of Australia and South Africa, and can rapidly image optical transients at a longitude not monitored by other similar facilities. We report on first imaging tests of a pilot program of minor planet searches, and Target of Opportunity observations triggered by the Swift satellite. In 12 months, 6 gamma-ray burst afterglows were detected, with estimated magnitudes; two of them, GRB 090205 (z = 4.65) and GRB 090516 (z = 4.11), are among the most distant optical transients imaged by an Australian telescope. Many asteroids were observed in a systematic 3-month search. In September 2009, an automatic telescope control system was installed, which will be used to link the facility to a global robotic telescope network; future targets will include fast optical transients triggered by high-energy satellites, radio transient detections, and LIGO gravitational wave candidate events. We also outline the importance of the facility as a potential tool for education, training, and public outreach.
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Burhanudin, U. F., J. R. Maund, T. Killestein, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, et al. "Light-curve classification with recurrent neural networks for GOTO: dealing with imbalanced data." Monthly Notices of the Royal Astronomical Society 505, no. 3 (May 28, 2021): 4345–61. http://dx.doi.org/10.1093/mnras/stab1545.
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ABSTRACT The advent of wide-field sky surveys has led to the growth of transient and variable source discoveries. The data deluge produced by these surveys has necessitated the use of machine learning (ML) and deep learning (DL) algorithms to sift through the vast incoming data stream. A problem that arises in real-world applications of learning algorithms for classification is imbalanced data, where a class of objects within the data is underrepresented, leading to a bias for overrepresented classes in the ML and DL classifiers. We present a recurrent neural network (RNN) classifier that takes in photometric time-series data and additional contextual information (such as distance to nearby galaxies and on-sky position) to produce real-time classification of objects observed by the Gravitational-wave Optical Transient Observer, and use an algorithm-level approach for handling imbalance with a focal loss function. The classifier is able to achieve an Area Under the Curve (AUC) score of 0.972 when using all available photometric observations to classify variable stars, supernovae, and active galactic nuclei. The RNN architecture allows us to classify incomplete light curves, and measure how performance improves as more observations are included. We also investigate the role that contextual information plays in producing reliable object classification.
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Heinzel, J., M. W. Coughlin, T. Dietrich, M. Bulla, S. Antier, N. Christensen, D. A. Coulter, R. J. Foley, L. Issa, and N. Khetan. "Comparing inclination-dependent analyses of kilonova transients." Monthly Notices of the Royal Astronomical Society 502, no. 2 (January 28, 2021): 3057–65. http://dx.doi.org/10.1093/mnras/stab221.
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ABSTRACT The detection of the optical transient AT2017gfo proved that binary neutron star mergers are progenitors of kilonovae (KNe). Using a combination of numerical-relativity and radiative-transfer simulations, the community has developed sophisticated models for these transients for a wide portion of the expected parameter space. Using these simulations and surrogate models made from them, it has been possible to perform Bayesian inference of the observed signals to infer properties of the ejected matter. It has been pointed out that combining inclination constraints derived from the KN with gravitational-wave measurements increases the accuracy with which binary parameters can be estimated, in particular breaking the distance-inclination degeneracy from gravitational wave inference. To avoid bias from the unknown ejecta geometry, constraints on the inclination angle for AT2017gfo should be insensitive to the employed models. In this work, we compare different assumptions about the ejecta and radiative reprocesses used by the community and we investigate their impact on the parameter inference. While most inferred parameters agree, we find disagreement between posteriors for the inclination angle for different geometries that have been used in the current literature. According to our study, the inclusion of reprocessing of the photons between different ejecta types improves the modeling fits to AT2017gfo and, in some cases, affects the inferred constraints. Our study motivates the inclusion of large ∼ 1-mag uncertainties in the KN models employed for Bayesian analysis to capture yet unknown systematics, especially when inferring inclination angles, although smaller uncertainties seem appropriate to capture model systematics for other intrinsic parameters. We can use this method to impose soft constraints on the ejecta geometry of the KN AT2017gfo.
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Frostig, Danielle, Sylvia Biscoveanu, Geoffrey Mo, Viraj Karambelkar, Tito Dal Canton, Hsin-Yu Chen, Mansi Kasliwal, et al. "An Infrared Search for Kilonovae with the WINTER Telescope. I. Binary Neutron Star Mergers." Astrophysical Journal 926, no. 2 (February 1, 2022): 152. http://dx.doi.org/10.3847/1538-4357/ac4508.
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Abstract The Wide-Field Infrared Transient Explorer (WINTER) is a new 1 deg2 seeing-limited time-domain survey instrument designed for dedicated near-infrared follow-up of kilonovae from binary neutron star (BNS) and neutron star–black hole mergers. WINTER will observe in the near-infrared Y, J, and short-H bands (0.9–1.7 μm, to J AB = 21 mag) on a dedicated 1 m telescope at Palomar Observatory. To date, most prompt kilonova follow-up has been in optical wavelengths; however, near-infrared emission fades more slowly and depends less on geometry and viewing angle than optical emission. We present an end-to-end simulation of a follow-up campaign during the fourth observing run (O4) of the LIGO, Virgo, and KAGRA interferometers, including simulating 625 BNS mergers, their detection in gravitational waves, low-latency and full parameter estimation skymaps, and a suite of kilonova lightcurves from two different model grids. We predict up to five new kilonovae independently discovered by WINTER during O4, given a realistic BNS merger rate. Using a larger grid of kilonova parameters, we find that kilonova emission is ≈2 times longer lived and red kilonovae are detected ≈1.5 times further in the infrared than in the optical. For 90% localization areas smaller than 150 (450) deg2, WINTER will be sensitive to more than 10% of the kilonova model grid out to 350 (200) Mpc. We develop a generalized toolkit to create an optimal BNS follow-up strategy with any electromagnetic telescope and present WINTER’s observing strategy with this framework. This toolkit, all simulated gravitational-wave events, and skymaps are made available for use by the community.
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Fragione, Giacomo, Rosalba Perna, and Abraham Loeb. "Calibrating the binary black hole population in nuclear star clusters through tidal disruption events." Monthly Notices of the Royal Astronomical Society 500, no. 4 (November 11, 2020): 4307–18. http://dx.doi.org/10.1093/mnras/staa3493.
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ABSTRACT As the sensitivity of gravitational wave (GW) instruments improves and new networks start operating, hundreds of merging stellar-mass black holes (SBHs) and intermediate-mass black holes (IMBHs) are expected to be observed in the next few years. The origin and distribution of SBH and IMBH binaries in various dynamical environments is a fundamental scientific question in GW astronomy. In this paper, we discuss ways tidal disruption events (TDEs) may provide a unique electromagnetic window into the assembly and merger of binary SBHs and IMBHs in nuclear star clusters (NSCs). We discuss how the host NSC mass and density and the slope of the BH mass function set the orbital properties and the masses of the binaries that undergo a TDE. For typical NSC properties, we predict a TDE rate of ∼10−6–10−7 yr−1 per galaxy. The light curve of TDEs in NSCs could be interrupted and modulated by the companion BH on the orbital period of the binary. These should be readily detectable by optical transient surveys such as the Zwicky Transient Facility and LSST.
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Dutton, Dylan A., Daniel E. Reichart, Joshua B. Haislip, Vladimir V. Kouprianov, Omar H. Shaban, and Alan Vasquez Soto. "Skynet’s New Observing Mode: The Campaign Manager." Publications of the Astronomical Society of the Pacific 134, no. 1031 (January 1, 2022): 015001. http://dx.doi.org/10.1088/1538-3873/ac3f7c.
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Abstract Built in 2004, the Skynet robotic telescope network originally consisted of six 0.4 m telescopes located at the Cerro-Tololo Inter-American Observatory in the Chilean Andes. The network was designed to carry out simultaneous multi-wavelength observations of gamma-ray bursts (GRBs) when they are only tens of seconds old. To date, the network has been expanded to ≈20 telescopes, including a 20 m radio telescope, that span four continents and five countries. The Campaign Manager (CM) is a new observing mode that has been developed for Skynet. Available to all Skynet observers, the CM semi-autonomously and indefinitely scales and schedules exposures on the observer’s behalf while allowing for modification to scaling parameters in real time. The CM is useful for follow up to various transient phenomena including gravitational-wave events, GRB localizations, young supernovae, and eventually, sufficiently bright Argus Optical Array and Large Synoptic Survey Telescope events.
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Almualla, Mouza, Shreya Anand, Michael W. Coughlin, Tim Dietrich, Nidhal Guessoum, Ana Sagués Carracedo, Tomás Ahumada, et al. "Optimizing serendipitous detections of kilonovae: cadence and filter selection." Monthly Notices of the Royal Astronomical Society 504, no. 2 (April 19, 2021): 2822–31. http://dx.doi.org/10.1093/mnras/stab1090.
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ABSTRACT The rise of multimessenger astronomy has brought with it the need to exploit all available data streams and learn more about the astrophysical objects that fall within its breadth. One possible avenue is the search for serendipitous optical/near-infrared counterparts of gamma-ray bursts (GRBs) and gravitational-wave (GW) signals, known as kilonovae. With surveys such as the Zwicky Transient Facility (ZTF), which observes the sky with a cadence of ∼3 d, the existing counterpart locations are likely to be observed; however, due to the significant amount of sky to explore, it is difficult to search for these fast-evolving candidates. Thus, it is beneficial to optimize the survey cadence for realtime kilonova identification and enable further photometric and spectroscopic observations. We explore how the cadence of wide field-of-view surveys like ZTF can be improved to facilitate such identifications. We show that with improved observational choices, e.g. the adoption of three epochs per night on a ∼ nightly basis, and the prioritization of redder photometric bands, detection efficiencies improve by about a factor of two relative to the nominal cadence. We also provide realistic hypothetical constraints on the kilonova rate as a form of comparison between strategies, assuming that no kilonovae are detected throughout the long-term execution of the respective observing plan. These results demonstrate how an optimal use of ZTF increases the likelihood of kilonova discovery independent of GWs or GRBs, thereby allowing for a sensitive search with less interruption of its nominal cadence through Target of Opportunity programs.
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Fargion, D., M. Yu Khlopov, and P. Oliva. "Could GRB170817A be really correlated to an NS–NS merging?" International Journal of Modern Physics D 27, no. 06 (April 2018): 1841001. http://dx.doi.org/10.1142/s0218271818410018.
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The exciting development of gravitational wave (GW) astronomy in the correlation of LIGO and VIRGO detection of GW signals makes possible to expect registration of effects of not only binary black hole (BH) coalescence but also binary neutron star (NS) merging accompanied by electromagnetic (gamma ray burst; GRB) signal. Here we consider the possibility that an NS, merging in an NS–NS or NS–BH system might be (soon) observed in correlation with any LIGO–VIRGO GWs detection. We analyze as an example the recent case of the short GRB170817A observed by Fermi and integral. The associated optical transient (OT) source in NGC4993 implies a rare near source, a consequent averaged large rate of such events (almost) compatible with expected NS–NS merging rate. However the expected beamed GRB (or short GRB) may be mostly aligned to a different direction than ours. Therefore, even soft GRB photons, spread more than hard ones, might be hardly able to shower to us. Nevertheless, a prompt spiraling electron turbine jet in largest magnetic fields, at the base of the NS–NS collapse, might shine by its tangential synchrotron radiation in spread way with its skimming photons shining in large open disk. The consequent solid angle for such soft disk gamma radiation may be large enough to be nevertheless often observed.
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Shrestha, M., I. A. Steele, S. Kobayashi, N. Jordana-Mitjans, R. J. Smith, H. Jermak, D. Arnold, C. G. Mundell, A. Gomboc, and C. Guidorzi. "GRB 191016A: a highly collimated gamma-ray burst jet with magnetized energy injection." Monthly Notices of the Royal Astronomical Society 509, no. 4 (November 24, 2021): 5964–73. http://dx.doi.org/10.1093/mnras/stab3368.
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ABSTRACT Long gamma-ray burst GRB 191016A was a bright and slow rising burst that was detected by the Swift satellite and followed up by ground based Liverpool Telescope (LT). LT follow up started 2411 s after the Swift Burst Alert Telescope (BAT) trigger using imager IO:O around the time of the late optical peak. From 3987–7687 s, we used the LT polarimeter RINGO3 to make polarimetric and photometric observations of the GRB simultaneously in the V, R, and I bands. The combined optical light curve shows an initial late peak followed by a decline until 6147 s, 6087 s, and 5247 s for I, R, and V filters respectively followed by a flattening phase. There is evidence of polarization at all phases including polarization ($P = 14.6 \pm 7.2 {{\ \rm per\ cent}}$) which is coincident with the start of the flattening phase. The combination of the light curve morphology and polarization measurement favours an energy injection scenario where slower magnetized ejecta from the central engine catches up with the decelerating blast wave. We calculate the minimum energy injection to be ΔE/E > 0.36. At a later time, combining the optical light curve from Burst Observer and Optical Transient Exploring System (BOOTES) (reported via GCN) and IO:O we see evidence of a jet break with jet opening angle 2°.
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Valeev, A. F., A. J. Castro-Tirado, Y. D. Hu, V. V. Sokolov, I. Agudo, M. D. Caballero-García, J. Cepa, et al. "OPTICAL SPECTROSCOPY OF CANDIDATES IN THE LIGO/VIRGO BINARY MERGER ERROR BOXES." Revista Mexicana de Astronomía y Astrofísica Serie de Conferencias 53 (September 1, 2021): 83–90. http://dx.doi.org/10.22201/ia.14052059p.2021.53.19.
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We performed optical spectroscopy of the candidates inside the gravitational wave errorboxes (S190408an, S190425z, S190426c, S190510g, S190728q, S190814bv). The spectral classification of 34 transients observed with the 10.4m Gran Telescopio de Canarias prior to 1 Sep 2019 is presented. We ruled out the association of these candidates with gravitational wave events.
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Ni, Wei-Tou. "Gravitational wave detection in space." International Journal of Modern Physics D 25, no. 14 (December 2016): 1630001. http://dx.doi.org/10.1142/s0218271816300019.
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Gravitational Wave (GW) detection in space is aimed at low frequency band (100[Formula: see text]nHz–100[Formula: see text]mHz) and middle frequency band (100[Formula: see text]mHz–10[Formula: see text]Hz). The science goals are the detection of GWs from (i) Supermassive Black Holes; (ii) Extreme-Mass-Ratio Black Hole Inspirals; (iii) Intermediate-Mass Black Holes; (iv) Galactic Compact Binaries and (v) Relic GW Background. In this paper, we present an overview on the sensitivity, orbit design, basic orbit configuration, angular resolution, orbit optimization, deployment, time-delay interferometry (TDI) and payload concept of the current proposed GW detectors in space under study. The detector proposals under study have arm length ranging from 1000[Formula: see text]km to [Formula: see text][Formula: see text]km (8.6[Formula: see text]AU) including (a) Solar orbiting detectors — (ASTROD Astrodynamical Space Test of Relativity using Optical Devices (ASTROD-GW) optimized for GW detection), Big Bang Observer (BBO), DECi-hertz Interferometer GW Observatory (DECIGO), evolved LISA (e-LISA), Laser Interferometer Space Antenna (LISA), other LISA-type detectors such as ALIA, TAIJI etc. (in Earthlike solar orbits), and Super-ASTROD (in Jupiterlike solar orbits); and (b) Earth orbiting detectors — ASTROD-EM/LAGRANGE, GADFLI/GEOGRAWI/g-LISA, OMEGA and TIANQIN.
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Kasliwal, M. M., S. B. Cenko, L. P. Singer, A. Corsi, Y. Cao, T. Barlow, V. Bhalerao, et al. "iPTF SEARCH FOR AN OPTICAL COUNTERPART TO GRAVITATIONAL-WAVE TRANSIENT GW150914." Astrophysical Journal 824, no. 2 (June 16, 2016): L24. http://dx.doi.org/10.3847/2041-8205/824/2/l24.
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Mészáros, L., A. Pál, G. Csépány, K. Vida, L. Kriskovics, and K. Oláh. "EXPLORING THE TRANSIENT SKY WITH THE FLY'S EYE CAMERA SYSTEM." Revista Mexicana de Astronomía y Astrofísica Serie de Conferencias 51 (April 13, 2019): 116–23. http://dx.doi.org/10.22201/ia.14052059p.2019.51.19.
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To study astrophysical transit phenomena we follow an alternative strategy for getting high-cadence observations of the field. This can be achieved with our new Fly’s Eye Camera System that monitors the entire sky above 30◦ horizontal altitude. With this instrument one can observe all phenomena brighter than ∼ 15m in Sloan r-band (u’, g’,i’ and z’ filters are also available). If we stack together a few hour of images we canobserve ∼ 17 m faint sources. This small-sized instrument is designed for time-domain astronomy with its 150 sec cadence. Due to the hexapod-based motion control, the instrument can be installed anywhere without any modifications, it can accomplish sky tracking automatically. These parallel robots have 6 degrees of freedom (DoF), but since any kind of rotation can be done by using only 3 DoF, the tracking with hexapods is independent from the geographical coordinates. Even polar alignment is not required, because Fly’s Eye can calibrate itself based on its own observed data. The system is optimal for time-domain astronomy: detecting novae, supernovae, optical afterglows of gamma-ray bursts and other bright, fast transients, and, from the observation database such data can be obtained - even from before the discovery of the transient event. In the future when the direction of the gravitational waves will be defined precisely we will be able to detect their first multiwaveband counterparts. In addition the Fly’s Eye will support the “Transient Astrophysical Objects” project which will use two new 80 cm robotic telescopes for follow-up observations of transients.
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Stubbs, C. W. "Linking optical and infrared observations with gravitational wave sources through transient variability." Classical and Quantum Gravity 25, no. 18 (September 2, 2008): 184033. http://dx.doi.org/10.1088/0264-9381/25/18/184033.
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Soloviev, A. A., and Efim A. Khazanov. "Optical isolation in the LIGO gravitational wave laser detector in transient states." Quantum Electronics 42, no. 4 (April 27, 2012): 367–71. http://dx.doi.org/10.1070/qe2012v042n04abeh014817.
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Möller, A., B. E. Tucker, P. Armstrong, S. W. Chang, N. Lowson, C. A. Onken, F. Panther, et al. "First Results of the SkyMapper Transient Survey." Proceedings of the International Astronomical Union 14, S339 (November 2017): 3–6. http://dx.doi.org/10.1017/s1743921318002077.
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AbstractThe SkyMapper Transient survey (SMT) is exploring variability in the southern sky by performing (a) a rolling search to discover and study supernovæ, and (b) a Target of Opportunity programme that uses the robotic SkyMapper Telescope at Siding Spring Observatory. The supernova survey is obtaining a non-targeted sample of Type Ia supernovæ (SNe Ia) at low redshifts, z < 0.1, and studying other interesting transients found with the search strategy. We have a Target of Opportunity programme with an automatic response mechanism to search for optical counterparts to gravitational-wave and fast radio-burst events; it benefits from SkyMapper’s large field of view of 5.7 sq. deg. and a rapid data reduction pipeline.We present first results of the SMT survey. The SMT pipeline can process and obtain potential candidates within 12 hours of observation. It disentangles real transients from processing artefacts using a machine-learning algorithm. To date, SMT has discovered over 60 spectroscopically confirmed supernovæ, several peculiar objects, and over 40 SNe Ia including one (SNIa 2016hhd) which was found within the first few days of explosion. We have also participated in searches for optical counterparts of gravitational waves, fast radio bursts and other transients, and have published observations of the optical counterpart of the gravitational-wave event GW170817. We also participate in coordinated observations with the Deeper Wider Faster programme, and the Kepler K2 cosmology project.
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Chen, T. W. "The Electromagnetic Counterpart of the Gravitational Wave Source GW170817." Proceedings of the International Astronomical Union 14, S339 (November 2017): 56–60. http://dx.doi.org/10.1017/s1743921318002211.
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AbstractOn 17th August 2017 a strong source of gravitational waves was detected by the LIGO-Virgo collaboration. The signal lasted for 60 seconds, and the event was followed just 2 seconds later by a short burst of gamma-rays that was detected by Fermi and INTEGRAL. The gravitational-wave and gamma-ray source had consistent sky positions to within about 30 square degrees. Within 10 hours of the gravitational-wave source event, a fast fading optical and near-infrared counterpart was discovered, which was subsequently followed-up and studied intensively for several weeks and months by numerous facilities. This talk presented the results from our optical and near-infrared imaging and spectroscopic follow-up campaign of this unprecedented discovery, which was the first electromagnetic counterpart of a gravitational-wave source, the first identification of a neutron star–neutron star merger, and the first direct evidence of the source of r-process elements. It focussed on the results of the GROND and ePESSTO teams, showing that this remarkable transient truly opened up the era of multi-messenger astronomy.
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Lewis, Geraint F. "Gravitational microlensing time delays at high optical depth: image parities and the temporal properties of fast radio bursts." Monthly Notices of the Royal Astronomical Society 497, no. 2 (July 13, 2020): 1583–89. http://dx.doi.org/10.1093/mnras/staa2044.
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ABSTRACT Due to differing gravitational potentials and path lengths, gravitational lensing induces time delays between multiple images of a source that, for solar mass objects, are of the order of ∼10−5 s. If an astrophysically compact source, such as a fast radio burst (FRB), is observed through a region with a high optical depth of such microlensing masses, this gravitational lensing time delay can be imprinted on short time-scale transient signals. In this paper, we consider the impact of the parity of the macroimage on the resultant microlensing time delays. It is found that this parity is directly imprinted on the microlensing signal, with macroimages formed at minima of the time arrival surface beginning with the most highly magnified microimages and then progressing to the fainter microimages. For macroimages at the maxima of the time arrival surface, this situation is reversed, with fainter images observed first and finishing with the brightest microimages. For macroimages at saddle points, the signal again begins with fainter images, followed by brighter images before again fading through the fainter microimages. The growing populations of cosmologically distant bursty transient sources will undoubtedly result in the discovery of strong lensed, multiply imaged FRBs, which will be susceptible to microlensing by compact masses. With the temporal resolution being offered by modern and future facilities, the detection of microlensing-induced time delays will reveal the parities of the gravitational lens macroimages, providing additional constraints on macrolensing mass models and improving the efficacy of these transient sources as cosmological probes.
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Tucker, D. L., M. P. Wiesner, S. S. Allam, M. Soares-Santos, C. R. Bom, M. Butner, A. Garcia, et al. "SOAR/Goodman Spectroscopic Assessment of Candidate Counterparts of the LIGO/Virgo Event GW190814*." Astrophysical Journal 929, no. 2 (April 1, 2022): 115. http://dx.doi.org/10.3847/1538-4357/ac5b60.
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Abstract On 2019 August 14 at 21:10:39 UTC, the LIGO/Virgo Collaboration (LVC) detected a possible neutron star–black hole merger (NSBH), the first ever identified. An extensive search for an optical counterpart of this event, designated GW190814, was undertaken using the Dark Energy Camera on the 4 m Victor M. Blanco Telescope at the Cerro Tololo Inter-American Observatory. Target of Opportunity interrupts were issued on eight separate nights to observe 11 candidates using the 4.1 m Southern Astrophysical Research (SOAR) telescope’s Goodman High Throughput Spectrograph in order to assess whether any of these transients was likely to be an optical counterpart of the possible NSBH merger. Here, we describe the process of observing with SOAR, the analysis of our spectra, our spectroscopic typing methodology, and our resultant conclusion that none of the candidates corresponded to the gravitational wave merger event but were all instead other transients. Finally, we describe the lessons learned from this effort. Application of these lessons will be critical for a successful community spectroscopic follow-up program for LVC observing run 4 (O4) and beyond.
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Melandri, A., A. Rossi, S. Benetti, V. D’Elia, S. Piranomonte, E. Palazzi, A. J. Levan, et al. "Unveiling the enigma of ATLAS17aeu." Astronomy & Astrophysics 621 (January 2019): A81. http://dx.doi.org/10.1051/0004-6361/201833814.
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Aims. The unusual transient ATLAS17aeu was serendipitously detected within the sky localisation of the gravitational wave trigger GW 170104. The importance of a possible association with gravitational waves coming from a binary black hole merger led to an extensive follow-up campaign, with the aim of assessing a possible connection with GW 170104. Methods. With several telescopes, we carried out both photometric and spectroscopic observations of ATLAS17aeu, for several epochs, between ∼3 and ∼230 days after the first detection. Results. We studied in detail the temporal and spectroscopic properties of ATLAS17aeu and its host galaxy. Although at low significance and not conclusive, we found similarities to the spectral features of a broad-line supernova superposed onto an otherwise typical long-GRB afterglow. Based on analysis of the optical light curve, spectrum, and host galaxy spectral energy distribution, we conclude that the redshift of the source is probably z ≃ 0.5 ± 0.2. Conclusions. While the redshift range we have determined is marginally compatible with that of the gravitational wave event, the presence of a supernova component and the consistency of this transient with the Ep–Eiso correlation support the conclusion that ATLAS17aeu was associated with the long gamma-ray burst GRB 170105A. This rules out the association of the GRB 170105A/ATLAS17aeu transient with the gravitational wave event GW 170104, which was due to a binary black hole merger.
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Agayeva, S., S. Alishov, S. Antier, V. R. Ayvazian, J. M. Bai, A. Baransky, K. Barynova, et al. "GRANDMA: A NETWORK TO COORDINATE THEM ALL." Revista Mexicana de Astronomía y Astrofísica Serie de Conferencias 53 (September 1, 2021): 198–205. http://dx.doi.org/10.22201/ia.14052059p.2021.53.39.
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GRANDMA is an international project that coordinates telescope observations of transient sources with large localization uncertainties. Such sources include gravitational wave events, gamma-ray bursts and neutrino events. GRANDMA currently coordinates 25 telescopes (70 scientists), with the aim of optimizing the imaging strategy to maximize the probability of identifying an optical counterpart of a transient source. This paper describes the motivation for the project, organizational structure, methodology and initial results.
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Suvorov, Arthur G. "Wave-optical Effects in the Microlensing of Continuous Gravitational Waves by Star Clusters." Astrophysical Journal 930, no. 1 (April 28, 2022): 13. http://dx.doi.org/10.3847/1538-4357/ac5f45.
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Abstract Rapidly rotating neutron stars are promising sources for existing and upcoming gravitational-wave interferometers. While relatively dim, these systems are expected to emit continuously, allowing for signal to be accumulated through persistent monitoring over year-long timescales. If, at some point during the observational window, the source comes to lie behind a dense collection of stars, transient gravitational lensing may occur. Such events, though rare, would modulate the waveform, induce phase drifts, and ultimately affect parameter inferences concerning the nuclear equation of state and/or magnetic field structure of the neutron star. Importantly, the radiation wavelength will typically exceed the Schwarzschild radius of the individual perturbers in this scenario, implying that (micro)lensing occurs in the diffractive regime, where geometric optics does not apply. In this paper, we make use of numerical tools that borrow from Picard–Lefschetz theory to efficiently evaluate the relevant Fresnel–Kirchhoff integrals for n ≳ 102 microlenses. Modulated strain profiles are constructed both in general and for particular neutron star trajectories relative to some simulated macrolenses.
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Mundell, Carole, and Mark Sullivan. "Workshop on Extreme Physics." Proceedings of the International Astronomical Union 7, S285 (September 2011): 270. http://dx.doi.org/10.1017/s1743921312000725.
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SummaryNever before has there been such a wealth of versatile ground- and space-based facilities with which to detect variable emission across the electromagnetic spectrum and beyond, to non-EM signals such as neutrinos and gravitational waves, to probe the most extreme phenomena in the Universe. The variable sky is already providing a wealth of new and surprising observations of phenomena such as GRBs, SNe and AGN that are pushing current theories beyond the state of the art. Multi-messenger follow-up will soon become de rigeur, and upcoming radio and optical all-sky transient surveys will revolutionise the study of the transient Universe. In addition to the technical and data challenges presented by such surveys, a major new challenge will be the interpretation of the wealth of available data and the identification of the underlying physics of new classes of variable (and potentially exotic) objects. Theoretical predictions will be vital for interpreting these future transient discoveries.The goal of this workshop was to bring together theorists and observers in order to identify unexplored synergies across three main research areas of extreme physics: gamma-ray bursts, supernovæ and, more generically, relativistic jets. It aimed to discuss key outstanding questions in these rapidly moving fields, such as the composition and acceleration of GRB and AGN jets, GRB progenitors and central engines, the origin of the wide range of observed variability time-scales in GRB prompt and after-glow light curves and related cosmological applications, the physics of the newly-discovered ultra-luminous SN-like optical transients—as well as to speculate on what we might hope to discover with future technology.The workshop absorbed two 90-minute sessions, selecting 3 main science topics (Relativistic Jets, GRBs and SNe) which it organised as structured discussions driven by a series of short but provocative questions. The final session featured a panel-led debate but with full audience participation.
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Grado, A., E. Cappellaro, S. Covino, F. Getman, G. Greco, L. Limatola, S. Yang, et al. "Search for the optical counterpart of the GW170814 gravitational wave event with the VLT Survey Telescope." Monthly Notices of the Royal Astronomical Society 492, no. 2 (December 24, 2019): 1731–54. http://dx.doi.org/10.1093/mnras/stz3536.
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ABSTRACT We report on the search for the optical counterpart of the gravitational event GW170814, which was carried out with the VLT Survey Telescope (VST) by the GRAvitational Wave Inaf TeAm. Observations started 17.5 h after the Laser Interferometer Gravitational-wave Observatory (LIGO) and Virgo alert and we covered an area of 99 deg2 that encloses $\sim 77{{\ \rm per\ cent}}$ and $\sim 59{{\ \rm per\ cent}}$ of the initial and refined localization probability regions, respectively. A total of six epochs were secured over nearly two months. The survey reached an average limiting magnitude of 22 AB mag in the r band. After assuming the model described in Perna, Lazzati & Farr, that derives as possible optical counterpart of a BBH (binary black hole) event a transient source declining in about one day, we have computed a survey efficiency of about $5{{\ \rm per\ cent}}$. This paper describes the VST observational strategy and the results obtained by our analysis pipelines developed to search for optical transients in multi-epoch images. We report the catalogue of the candidates with possible identifications based on light-curve fitting. We have identified two dozens of SNe, nine AGNs, and one QSO. Nineteen transients characterized by a single detection were not classified. We have restricted our analysis only to the candidates that fall into the refined localization map. None out of 39 left candidates could be positively associated with GW170814. This result implies that the possible emission of optical radiation from a BBH merger had to be fainter than r ∼ 22 (Loptical ∼ 1.4 × 1042 erg s−1) on a time interval ranging from a few hours up to two months after the gravitational wave event.
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Wong, Fu Mauh, Chee Keong Chong, and K. N. Seetharamu. "Transient Thermal Analysis of Wave Soldering Process for an Optical Encoder Module." Journal of Microelectronics and Electronic Packaging 1, no. 3 (July 1, 2004): 145–56. http://dx.doi.org/10.4071/1551-4897-1.3.145.
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Severe delamination at the interfaces of leadframe/mold compound and leadframe/die attach epoxy has been observed right after the wave soldering process for an optical encoder package. During wave soldering process, package is heated up by the hot ambient and the molten solder. As temperature increases, package is more prone to delamination due to degradation of adhesion strength. Finite Element Analysis (FEA) has been conducted to model the wave soldering process using the measured lead temperature as thermal boundary condition. Convective heating and cooling are considered. The dynamic temperature response of the package has been captured and analyzed. Several approaches inclusive of changing leadframe material, removing housing and altering mounting configuration, have been examined to obtain the best design that yield lowest package temperature. Experiment is conducted and the experimental results have been compared with the numerically predicted data and the agreement is good.
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Buckley, D. A. H. "The SALT Transient Programme." Proceedings of the International Astronomical Union 14, S339 (November 2017): 176–80. http://dx.doi.org/10.1017/s174392131800251x.
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AbstractThe SALT transient follow-up programme began in 2016 and will continue for 5 semesters (until 31 Oct 2018), with an expectation of renewal thereafter. It is currently the only SALT Large Science Programme, and was awarded ~250 ksec. per semester, with a significant fraction (60%) given for the highest priority target-of-opportunity time. The aim is to characterise and study transients across a wide range of classes, currently including (from closest to most distant) cataclysmic variables, novæ and other associated eruptive variables, low- and high-mass X-ray binaries, OGLE and Gaia transients (including tidal disruption events), super-luminous and unusual core-collapse supernovæ, kilonovæ and other candidate optical counterparts to gravitational-wave events, flaring blazars and AGN, and gamma-ray bursts. This programme currently involves four SALT partners, of which South Africa is the major contributor of time (74%) and resources and includes five institutions with over 30 co-investigators. This talk reviewed the nature of the programme and highlighted some of the results to date.
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Oates, S. R., F. E. Marshall, A. A. Breeveld, N. P. M. Kuin, P. J. Brown, M. De Pasquale, P. A. Evans, et al. "Swift/UVOT follow-up of gravitational wave alerts in the O3 era." Monthly Notices of the Royal Astronomical Society 507, no. 1 (August 5, 2021): 1296–317. http://dx.doi.org/10.1093/mnras/stab2189.
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ABSTRACT In this paper, we report on the observational performance of the Swift Ultra-violet/Optical Telescope (UVOT) in response to the gravitational wave (GW) alerts announced by the Advanced Laser Interferometer Gravitational Wave Observatory and the Advanced Virgo detector during the O3 period. We provide the observational strategy for follow-up of GW alerts and provide an overview of the processing and analysis of candidate optical/UV sources. For the O3 period, we also provide a statistical overview and report on serendipitous sources discovered by Swift/UVOT. Swift followed 18 GW candidate alerts, with UVOT observing a total of 424 deg2. We found 27 sources that changed in magnitude at the 3σ level compared with archival u- or g-band catalogued values. Swift/UVOT also followed up a further 13 sources reported by other facilities during the O3 period. Using catalogue information, we divided these 40 sources into five initial classifications: 11 candidate active galactic nuclei (AGNs)/quasars, three cataclysmic variables (CVs), nine supernovae, 11 unidentified sources that had archival photometry, and six uncatalogued sources for which no archival photometry was available. We have no strong evidence to identify any of these transients as counterparts to the GW events. The 17 unclassified sources are likely a mix of AGN and a class of fast-evolving transient, and one source may be a CV.
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Andreoni, Igor, Michael W. Coughlin, Mouza Almualla, Eric C. Bellm, Federica B. Bianco, Mattia Bulla, Antonino Cucchiara, et al. "Optimizing Cadences with Realistic Light-curve Filtering for Serendipitous Kilonova Discovery with Vera Rubin Observatory." Astrophysical Journal Supplement Series 258, no. 1 (December 22, 2021): 5. http://dx.doi.org/10.3847/1538-4365/ac3bae.
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Abstract Current and future optical and near-infrared wide-field surveys have the potential to find kilonovae, the optical and infrared counterparts to neutron star mergers, independently of gravitational-wave or high-energy gamma-ray burst triggers. The ability to discover fast and faint transients such as kilonovae largely depends on the area observed, the depth of those observations, the number of revisits per field in a given time frame, and the filters adopted by the survey; it also depends on the ability to perform rapid follow-up observations to confirm the nature of the transients. In this work, we assess kilonova detectability in existing simulations of the Legacy Survey of Space and Time strategy for the Vera C. Rubin Wide Fast Deep survey, with focus on comparing rolling to baseline cadences. Although currently available cadences can enable the detection of >300 kilonovae out to ∼1400 Mpc over the 10 year survey, we can expect only 3–32 kilonovae similar to GW170817 to be recognizable as fast-evolving transients. We also explore the detectability of kilonovae over the plausible parameter space, focusing on viewing angle and ejecta masses. We find that observations in redder izy bands are crucial for identification of nearby (within 300 Mpc) kilonovae that could be spectroscopically classified more easily than more distant sources. Rubin’s potential for serendipitous kilonova discovery could be increased by gain of efficiency with the employment of individual 30 s exposures (as opposed to 2 × 15 s snap pairs), with the addition of red-band observations coupled with same-night observations in g or r bands, and possibly with further development of a new rolling-cadence strategy.
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Luo, Zeyuan, Zanhao Fu, and Qiwei Xu. "An Adaptive Multi-Dimensional Vehicle Driving State Observer Based on Modified Sage–Husa UKF Algorithm." Sensors 20, no. 23 (December 2, 2020): 6889. http://dx.doi.org/10.3390/s20236889.
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An accurate vehicle driving state observer is a necessary condition for a safe automotive electronic control system. Vehicle driving state observer is challenged by unknown measurement noise and transient disturbances caused by complex working conditions and sensor failure. For the classical adaptive unscented Kalman filter (AUKF) algorithm, transient disturbances will cause the failure of state estimation and affect the subsequent process. This paper proposes an AUKF based on a modified Sage–Husa filter and divergence calculation technique for multi-dimensional vehicle driving state observation. Based on the seven-degrees-of-freedom vehicle model and the Dugoff tire model, the proposed algorithm corrects the measurement noise by using modified Sage–Husa maximum posteriori. To reduce the influence of transient disturbance on the subsequent process, covariance matrix is updated after divergence is detected. The effectiveness of the algorithm is tested on the double lane change and Sine Wave road conditions. The robustness of the algorithm is tested under severe transient disturbance. The results demonstrate that the modified Sage–Husa UKF algorithm can accurately detect transient disturbance and effectively reduce the resulted accumulated error. Compared to classical AUKF, our algorithm significantly improves the accuracy and robustness of vehicle driving state estimation. The research in this paper provides a reference for multi-dimensional data processing under changeable vehicle driving states.
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Artola, Rodolfo, Martin Beroiz, Juan Cabral, Richard Camuccio, Moises Castillo, Vahram Chavushyan, Carlos Colazo, et al. "TOROS optical follow-up of the advanced LIGO–VIRGO O2 second observational campaign." Monthly Notices of the Royal Astronomical Society 493, no. 2 (January 3, 2020): 2207–14. http://dx.doi.org/10.1093/mnras/stz3634.
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ABSTRACT We present the methods and results of the optical follow-up, conducted by the Transient Optical Robotic Observatory of the South Collaboration, of gravitational wave events detected during the Advanced LIGO–Virgo second observing run (2016 November–2017 August). Given the limited field of view (∼100 arcmin) of our observational instrumentation, we targeted galaxies within the area of high localization probability that were observable from our sites. We analysed the observations using difference imaging, followed by a random forest algorithm to discriminate between real and spurious transients. Our observations were conducted using telescopes at Estación Astrofísica de Bosque Alegre, Cerro Tololo Inter-American Observatory, the Dr. Cristina V. Torres Memorial Astronomical Observatory, and an observing station in Salta, Argentina.
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Rafiee-Dehkharghani, R., Dipanshu Bansal, Amjad J. Aref, and Gary F. Dargush. "Analysis and Optimal Design of Stress Wave Intensity Attenuation in Layered Structures." International Journal of Structural Stability and Dynamics 18, no. 01 (January 2018): 1850015. http://dx.doi.org/10.1142/s0219455418500153.
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Within the framework of linear two-dimensional elastodynamics, stress wave intensity attenuators are studied under material and boundary condition discontinuities collectively. The influence of various parameters on the efficiency of stress wave attenuators is investigated thoroughly and a comprehensive understanding of the response is developed under dynamic loadings for a wide range of frequencies. In particular, the effect of in-plane and out-of-plane dimensions, incident wave frequencies (wavelength), rigidity of the host structure, and impedance mismatch between different layers have been examined. The dependence of stress wave attenuator efficiency and robustness are found to be a complex function of all relevant parameters, and performance is observed to vary significantly for various combinations. To illustrate the significance of combined effects of various parameters on the potential efficiency of the stress wave intensity attenuators, an optimization problem is solved. An optimal material set-up of a 12-layered structure, subjected to transient loadings with varying durations and wide range of frequency contents, is presented. A coupled genetic algorithm-finite element methodology is developed specifically for the optimal design of layered structures. This methodology is highly suitable for investigating the solution space that is too large to be explored by an exhaustive parametric study. The results of the optimal designs evidently show that the efficiency of the stress wave attenuators depends significantly on the duration of transient loading, and high efficiency can be attained for short durations.
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ZHAO, MING, and MOHAMED S. GHIDAOUI. "TRANSIENT DYNAMICS OF STREAK AND LONGITUDINAL VORTICES IN SHEAR FLOW WITH WAVE." International Journal of Modern Physics: Conference Series 19 (January 2012): 139–53. http://dx.doi.org/10.1142/s2010194512008689.
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Langmuir circulations are alternating right and left helical vortices in the ocean having horizontal axes parallel to the wind. They are manifested by floating material on the ocean surface as streaks. The laboratory wind driven shear flow demonstrate streak feature with/without wave condition. When the wave is present the explanation of results with Craik-Leibovich instability mechanism, originally proposed for weak current shear in ocean, is not appropriate for some problem as in the laboratory the current shear is strong. The existing normal mode analysis based on the generalized Lagrangian mean formulation for wave with strong shear is not able to capture the fully dynamics of streak and longitudinal vortices. We extend Craik-Leibovich theory to strong shear in Eulerian framework but focusing on the fully perturbation evolution dynamics. Transient dynamics of perturbation is studied with an initial value problem. In this approach the effect of shear and wave and its interaction are made clear. The transient growth in the time period without wave is significant and is crucial to the initial preferred wave number observed in the experiments. The optimal longitudinal vortex form perturbation is searched and the preferred spanwise wave number predicted is well consistent with experimental data of wind shear and wave.
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Amati, L., P. T. O’Brien, D. Götz, E. Bozzo, A. Santangelo, N. Tanvir, F. Frontera, et al. "The THESEUS space mission: science goals, requirements and mission concept." Experimental Astronomy 52, no. 3 (November 9, 2021): 183–218. http://dx.doi.org/10.1007/s10686-021-09807-8.
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AbstractTHESEUS, one of the two space mission concepts being studied by ESA as candidates for next M5 mission within its Comsic Vision programme, aims at fully exploiting Gamma-Ray Bursts (GRB) to solve key questions about the early Universe, as well as becoming a cornerstone of multi-messenger and time-domain astrophysics. By investigating the first billion years of the Universe through high-redshift GRBs, THESEUS will shed light on the main open issues in modern cosmology, such as the population of primordial low mass and luminosity galaxies, sources and evolution of cosmic re-ionization, SFR and metallicity evolution up to the “cosmic dawn” and across Pop-III stars. At the same time, the mission will provide a substantial advancement of multi-messenger and time-domain astrophysics by enabling the identification, accurate localisation and study of electromagnetic counterparts to sources of gravitational waves and neutrinos, which will be routinely detected in the late ‘20s and early ‘30s by the second and third generation Gravitational Wave (GW) interferometers and future neutrino detectors, as well as of all kinds of GRBs and most classes of other X/gamma-ray transient sources. Under all these respects, THESEUS will provide great synergies with future large observing facilities in the multi-messenger domain. A Guest Observer programme, comprising Target of Opportunity (ToO) observations, will expand the science return of the mission, to include, e.g., solar system minor bodies, exoplanets, and AGN.
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Margutti, Raffaella, and Ryan Chornock. "First Multimessenger Observations of a Neutron Star Merger." Annual Review of Astronomy and Astrophysics 59, no. 1 (September 8, 2021): 155–202. http://dx.doi.org/10.1146/annurev-astro-112420-030742.
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We describe the first observations of the same celestial object with gravitational waves and light. ▪ GW170817 was the first detection of a neutron star merger with gravitational waves. ▪ The detection of a spatially coincident weak burst of gamma-rays (GRB 170817A) 1.7 s after the merger constituted the first electromagnetic detection of a gravitational wave source and established a connection between at least some cosmic short gamma-ray bursts (SGRBs) and binary neutron star mergers. ▪ A fast-evolving optical and near-infrared transient (AT 2017gfo) associated with the event can be interpreted as resulting from the ejection of ∼0.05 M⊙ of material enriched in r-process elements, finally establishing binary neutron star mergers as at least one source of r-process nucleosynthesis. ▪ Radio and X-ray observations revealed a long-rising source that peaked ∼160,d after the merger. Combined with the apparent superluminal motion of the associated very long baseline interferometry source, these observations show that the merger produced a relativistic structured jet whose core was oriented ≈20 deg from the line of sight and with properties similar to SGRBs. The jet structure likely results from interaction between the jet and the merger ejecta. ▪ The electromagnetic and gravitational wave information can be combined to produce constraints on the expansion rate of the Universe and the equation of state of dense nuclear matter. These multimessenger endeavors will be a major emphasis of future work.
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Petrov, Polina, Leo P. Singer, Michael W. Coughlin, Vishwesh Kumar, Mouza Almualla, Shreya Anand, Mattia Bulla, Tim Dietrich, Francois Foucart, and Nidhal Guessoum. "Data-driven Expectations for Electromagnetic Counterpart Searches Based on LIGO/Virgo Public Alerts." Astrophysical Journal 924, no. 2 (January 1, 2022): 54. http://dx.doi.org/10.3847/1538-4357/ac366d.
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Abstract Searches for electromagnetic counterparts of gravitational-wave signals have redoubled since the first detection in 2017 of a binary neutron star merger with a gamma-ray burst, optical/infrared kilonova, and panchromatic afterglow. Yet, one LIGO/Virgo observing run later, there has not yet been a second, secure identification of an electromagnetic counterpart. This is not surprising given that the localization uncertainties of events in LIGO and Virgo’s third observing run, O3, were much larger than predicted. We explain this by showing that improvements in data analysis that now allow LIGO/Virgo to detect weaker and hence more poorly localized events have increased the overall number of detections, of which well-localized, gold-plated events make up a smaller proportion overall. We present simulations of the next two LIGO/Virgo/KAGRA observing runs, O4 and O5, that are grounded in the statistics of O3 public alerts. To illustrate the significant impact that the updated predictions can have, we study the follow-up strategy for the Zwicky Transient Facility. Realistic and timely forecasting of gravitational-wave localization accuracy is paramount given the large commitments of telescope time and the need to prioritize which events are followed up. We include a data release of our simulated localizations as a public proposal planning resource for astronomers.
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Lozing, Natalia A., Maxim G. Gladush, Ivan Yu Eremchev, Eugeniy A. Ekimov, and Andrey V. Naumov. "Spontaneous transitions to enhanced fluorescence for GeV centers in a single microcrystalline diamond." EPJ Web of Conferences 190 (2018): 04012. http://dx.doi.org/10.1051/epjconf/201819004012.
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We propose a theoretical explanation of spontaneous transitions between dim and bright fluorescence intensity states observed experimentally in a microcrystal of diamond with germanium-vacancy colour centres driven by a continuous wave laser. We use a generalized system of optical Maxwell-Bloch equations derived for an emitter in an ensemble of motionless similar particles embedded in a dielectric medium, which is transparent for the incident light. A numerical analysis of transient regimes and several models of slow damping of the bright luminescence mode are reported.
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Lin, Eric, Calvin Craig, Marcel Lamothe, Marinko V. Sarunic, Mirza Faisal Beg, and Glen F. Tibbits. "Construction and use of a zebrafish heart voltage and calcium optical mapping system, with integrated electrocardiogram and programmable electrical stimulation." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 308, no. 9 (May 1, 2015): R755—R768. http://dx.doi.org/10.1152/ajpregu.00001.2015.
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Zebrafish are increasingly being used as a model of vertebrate cardiology due to mammalian-like cardiac properties in many respects. The size and fecundity of zebrafish make them suitable for large-scale genetic and pharmacological screening. In larger mammalian hearts, optical mapping is often used to investigate the interplay between voltage and calcium dynamics and to investigate their respective roles in arrhythmogenesis. This report outlines the construction of an optical mapping system for use with zebrafish hearts, using the voltage-sensitive dye RH 237 and the calcium indicator dye Rhod-2 using two industrial-level CCD cameras. With the use of economical cameras and a common 532-nm diode laser for excitation, the rate dependence of voltage and calcium dynamics within the atrial and ventricular compartments can be simultaneously determined. At 140 beats/min, the atrial action potential duration was 36 ms and the transient duration was 53 ms. With the use of a programmable electrical stimulator, a shallow rate dependence of 3 and 4 ms per 100 beats/min was observed, respectively. In the ventricle the action potential duration was 109 ms and the transient duration was 124 ms, with a steeper rate dependence of 12 and 16 ms per 100 beats/min. Synchronous electrocardiograms and optical mapping recordings were recorded, in which the P-wave aligns with the atrial voltage peak and R-wave aligns with the ventricular peak. A simple optical pathway and imaging chamber are detailed along with schematics for the in-house construction of the electrocardiogram amplifier and electrical stimulator. Laboratory procedures necessary for zebrafish heart isolation, cannulation, and loading are also presented.
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Shimotsuma, Yasuhiko, Masaaki Sakakura, Kiyotaka Miura, Jiarong Qiu, Peter G. Kazansky, Koji Fujita, and Andkazuyuki Hirao. "Application of Femtosecond-Laser Induced Nanostructures in Optical Memory." Journal of Nanoscience and Nanotechnology 7, no. 1 (January 1, 2007): 94–104. http://dx.doi.org/10.1166/jnn.2007.18008.
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The femtosecond laser induced micro- and nanostructures for the application to the three-dimensional optical data storage are investigated. We have observed the increase of refractive index due to local densification and atomic defect generation, and demonstrated the real time observation of photothermal effect after the femtosecond laser irradiation inside a glass by the transient lens (TrL) method. The TrL signal showed a damped oscillation with about an 800 ps period. The essential feature of the oscillation can be reproduced by the pressure wave creation and propagation to the outward direction from the irradiated region. The simulation based on elastodynamics has shown that a large thermoelastic stress is relaxed by the generation of the pressure wave. In the case of soda-lime glass, the velocity of the pressure wave is almost same as the longitudinal sound velocity at room temperature (5.8 μm/ns). We have also observed the localized photo-reduction of Sm3+ to Sm2+ inside a transparent and colorless Sm3+-doped borate glass. Photoluminescence spectra showed that some the Sm3+ ions in the focal spot within the glass sample were reduced to Sm2+ ions after femtosecond laser irradiation. A photo-reduction bit of 200 nm in three-dimensions can be recorded with a femtosecond laser and readout clearly by detecting the fluorescence excited by Ar+ laser (λ = 488 nm). A photo-reduction bit can be also erased by photo-oxidation with a cw Ar+ laser (λ = 514 5 nm). Since photo-reduction bits can be spaced 150 nm apart in a layer within glass, a memory capacity of as high as 1 Tbit can be achieved in a glass piece with dimensions of 10 mm × 10 mm × 1 mm. We have also demonstrated the first observation of the polarization-dependent periodic nanostructure formation by the interference between femtosecond laser light and electron acoustic waves. The observed nanostructures are the smallest embedded structures ever created by light. The period of self-organized nanostructures can be controlled from ∼140 to 320 nm by the pulse energy and the number of irradiated pulses. Furthermore, we have also observed the self-assembled sub-wavelength periodic structures created in silica glass by femtosecond pulses on the plane of the propagation of light.
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Bhayadia, Amit, Anthony Olivett, Tarunraj Singh, and M. Amin Karami. "Input shaping for travelling wave generation." Smart Materials and Structures 31, no. 5 (March 22, 2022): 055006. http://dx.doi.org/10.1088/1361-665x/ac5c89.
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Abstract Travelling wave patterns observed in the movement of certain aquatic animals has motivated research in the modification of flow behavior, especially to deal with boundary layer separation in airplane wings. Research has shown that inducing travelling waves on the top surface of the wing can generate sufficient momentum to prevent boundary layer separation without increasing the drag. Due to this effect of propagating waves on the aerodynamics, generation of travelling waves on solid surfaces is being widely studied. Recently, methods such as two-mode excitation, active sink and impedance matching have shown promise in generation of uniform travelling waves in solids with the help of piezo electric actuators. Unfortunately, there are some challenges involved in the experimental application of these methods. Although these techniques have shown to be adequate in laboratory settings, they require laborious tuning procedures which do not guarantee desired trajectories and are followed in light of interference from unwanted modes and their transients. Some methods rely on selective mode excitation, which can cause interference from unwanted modes if the transient behavior of the system is not accounted for. Feed-forward input shaping control methods are proposed that augment the open-loop piezo actuation method (two-mode excitation) and provide a more robust method for generating uniform travelling waves. The input shaping control alters the reference signal such that the parasitic behavior of unnecessary modes is cancelled out. The combination of the mode suppression and selective mode excitation through input shaping is verified experimentally for generation of a smooth travelling waves in finite structures.
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Hartmann, Dieter H. "Multi-wavelength Flashes from GRBs." International Astronomical Union Colloquium 151 (1995): 367–75. http://dx.doi.org/10.1017/s0252921100035375.
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The mystery of the nature and origin of gamma-ray bursts (GRBs) has persisted over two decades of intensive research, observational and theoretical. The basic problem is the absence of quiescent or transient counterparts at other wavelengths, resulting in distance scale uncertainties of more than 10 orders of magnitude. Searches for counterparts are hampered by the lack of sufficiently accurate localizations and by a lack of criteria that uniquely identify the expected appearance of counterparts (although see Meszaros &: Rees 1993, Meszaros et al. 1994). The detection of archival optical transients (OT’s) inside γ-ray burst error boxes suggested burst recurrence and generated hope for a breakthrough in the γ-ray burst counterpart search (e.g., Schaefer 1990). However, counterparts of these OT’s have never been identified, and the reality of several archival images was questioned (Zytkow 1990, but see Schaefer 1990). The search for multi-wavelengths transients has recently been extended to neutrino- and gravitational wave emission. The status of multiwavelength surveys for quiescent or transient counterparts prior to 1988 was reviewed by Hartmann & Woosley (1988). Here we update that review and discuss “optical” emission in view of the current debate on the burster distance scale. Other recent reviews are by Schaefer (1994) and Greiner (1995).