Browsing by Author "Jonker, P. G."

Now showing 1 - 13 of 13
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    AT 2022aedm and a New Class of Luminous, Fast-cooling Transients in Elliptical Galaxies
    (2023) Nicholl, M.; Srivastav, S.; Fulton, M. D.; Gomez, S.; Huber, M. E.; Oates, S. R.; Ramsden, P.; Rhodes, L.; Smartt, S. J.; Smith, K. W.; Aamer, A.; Anderson, J. P.; Bauer, F. E.; Berger, E.; de Boer, T.; Chambers, K. C.; Charalampopoulos, P.; Chen, T. -w.; Fender, R. P.; Fraser, M.; Gao, H.; Green, D. A.; Galbany, L.; Gompertz, B. P.; Gromadzki, M.; Gutierrez, C. P.; Howell, D. A.; Inserra, C.; Jonker, P. G.; Kopsacheili, M.; Lowe, T. B.; Magnier, E. A.; Mccully, C.; Mcgee, S. L.; Moore, T.; Mueller-Bravo, T. E.; Newsome, M.; Gonzalez, E. Padilla; Pellegrino, C.; Pessi, T.; Pursiainen, M.; Rest, A.; Ridley, E. J.; Shappee, B. J.; Sheng, X.; Smith, G. P.; Terreran, G.; Tucker, M. A.; Vinko, J.; Wainscoat, R. J.; Wiseman, P.; Young, D. R.
    We present the discovery and extensive follow-up of a remarkable fast-evolving optical transient, AT 2022aedm, detected by the Asteroid Terrestrial impact Last Alert Survey (ATLAS). In the ATLAS o band, AT 2022aedm exhibited a rise time of 9 & PLUSMN; 1 days, reaching a luminous peak with M g & AP; -22 mag. It faded by 2 mag in the g band during the next 15 days. These timescales are consistent with other rapidly evolving transients, though the luminosity is extreme. Most surprisingly, the host galaxy is a massive elliptical with negligible current star formation. Radio and X-ray observations rule out a relativistic AT 2018cow-like explosion. A spectrum in the first few days after explosion showed short-lived He ii emission resembling young core-collapse supernovae, but obvious broad supernova features never developed; later spectra showed only a fast-cooling continuum and narrow, blueshifted absorption lines, possibly arising in a wind with v & AP; 2700 km s-1. We identify two further transients in the literature (Dougie in particular, as well as AT 2020bot) that share similarities in their luminosities, timescales, color evolution, and largely featureless spectra and propose that these may constitute a new class of transients: luminous fast coolers. All three events occurred in passive galaxies at offsets of & SIM;4-10 kpc from the nucleus, posing a challenge for progenitor models involving massive stars or black holes. The light curves and spectra appear to be consistent with shock breakout emission, though this mechanism is usually associated with core-collapse supernovae. The encounter of a star with a stellar-mass black hole may provide a promising alternative explanation.
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    Delayed appearance and evolution of coronal lines in the TDE AT2019qiz
    (Oxford University Press, 2023) Short, P.; Lawrence, A.; Nicholl, M.; Ward, M.; Reynolds, T. M.; Mattila, S.; Yin, C.; Arcavi, I; Carnall, A.; Charalampopoulos, P.; Gromadzki, M.; Jonker, P. G.; Kim, Sam; Leloudas, G.; Mandel, I; Onori, F.; Pursiainen, M.; Schulze, S.; Villforth, C.; Wevers, T.
    Tidal disruption events (TDEs) occur when a star gets torn apart by a supermassive black hole as it crosses its tidal radius. We present late-time optical and X-ray observations of the nuclear transient AT2019qiz, which showed the typical signs of an optical-UV transient class commonly believed to be TDEs. Optical spectra were obtained 428, 481, and 828 rest-frame days after optical light-curve peak, and a UV/X-ray observation coincided with the later spectrum. The optical spectra show strong coronal emission lines, including [Fe vii], [Fe x], [Fe xi], and [Fe xiv]. The Fe lines rise and then fall, except [Fe xiv] that appears late and rises. We observe increasing flux of narrow H & alpha; and H & beta; and a decrease in broad H & alpha; flux. The coronal lines have full width at half-maximum ranging from & SIM;150-300 km s(-1), suggesting they originate from a region between the broad- and narrow-line emitting gas. Between the optical flare and late-time observation, the X-ray spectrum softens dramatically. The 0.3-1 keV X-ray flux increases by a factor of & SIM;50, while the hard X-ray flux decreases by a factor of & SIM;6. Wide-field Infrared Survey Explorer fluxes also rose over the same period, indicating the presence of an infrared echo. With AT2017gge, AT2019qiz is one of two examples of a spectroscopically confirmed optical-UV TDE showing delayed coronal line emission, supporting speculations that Extreme Coronal Line Emitters in quiescent galaxies can be echos of unobserved past TDEs. We argue that the coronal lines, narrow lines, and infrared emission arise from the illumination of pre-existing material likely related to either a previous TDE or active galactic nucleus activity.
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    Extragalactic fast X-ray transient candidates discovered by Chandra (2000-2014)
    (2022) Quirola-Vasquez, J.; Bauer, F. E.; Jonker, P. G.; Brandt, W. N.; Yang, G.; Levan, A. J.; Xue, Y. Q.; Eappachen, D.; Zheng, X. C.; Luo, B.
    Context. Extragalactic fast X-ray transients (FXRTs) are short flashes of X-ray photons of unknown origin that last a few seconds to hours.
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    Extragalactic fast X-ray transient candidates discovered by Chandra (2014-2022)
    (2023) Quirola-Vasquez, J.; Bauer, F. E.; Jonker, P. G.; Brandt, W. N.; Yang, G.; Levan, A. J.; Xue, Y. Q.; Eappachen, D.; Camacho, E.; Ravasio, M. E.; Zheng, X. C.; Luo, B.
    Context. Extragalactic fast X-ray transients (FXTs) are short flashes of X-ray photons of unknown origin that last a few minutes to hours.
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    Investigating the off-axis GRB afterglow scenario for extragalactic fast X-ray transients
    (2024) Wichern, H. C. I.; Ravasio, M. E.; Jonker, P. G.; Quirola-Vasquez, J. A.; Levan, A. J.; Bauer, F. E.; Kann, D. A.
    Context. Extragalactic fast X-ray transients (FXTs) are short-duration (similar to ks) X-ray flashes of unknown origin, potentially arising from binary neutron star (BNS) mergers, tidal disruption events, or supernova shock breakouts. Aims. In the context of the BNS scenario, we investigate the possible link between FXTs and the afterglows of off-axis merger-induced gamma-ray bursts (GRBs). Methods. By modelling well-sampled broadband afterglows of 13 merger-induced GRBs, we make predictions for their X-ray light curve behaviour had they been observed off-axis, considering both a uniform jet with core angle theta(C) and a Gaussian-structured jet whose edge lies at an angle theta(W) = 2 theta(C). We compare their peak X-ray luminosity, duration, and temporal indices alpha (where F proportional to t(alpha)) with those of the currently known extragalactic FXTs. Results. Our analysis reveals that a slightly off-axis observing angle of theta(obs) approximate to (2.2 - 3)theta(C) and a structured jet are required to explain the shallow (|alpha|less than or similar to 0.3) temporal indices of the FXT light curves, which cannot be reproduced in the uniform-jet case at any viewing angle. In the case of a structured jet with truncation angle theta(W) = 2 theta(C), the distributions of the duration of the FXTs are consistent with those of the off-axis afterglows for the same range of observing angles, theta obs approximate to (2.2 - 3)theta(C). While the distributions of the off-axis peak X-ray luminosity are consistent only for theta(obs) = 2.2 theta(C), focussing on individual events with different intrinsic luminosities reveals that the match of all three properties (peak X-ray luminosity, duration and temporal indices) of the FXTs at the same viewing angle is possible in the range theta(obs) similar to (2.2 - 2.6)theta(C). Despite the small sample of GRBs analysed, these results show that there is a region of the parameter space - although quite limited - where the observational properties of off-axis GRB afterglow can be consistent with those of the newly discovered FXTs. Future observations of FXTs discovered by the recently launched Einstein Probe mission and GRB population studies combined with more complex afterglow models will shed light on this possible GRB-FXT connection, and eventually unveil the progenitors of some FXTs.
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    Observational constraints on the optical and near-infrared emission from the neutron star-black hole binary merger candidate S190814bv
    (2020) Ackley, K.; Amati, L.; Barbieri, C.; Bauer, F. E.; Benetti, S.; Bernardini, M. G.; Bhirombhakdi, K.; Botticella, M. T.; Branchesi, M.; Brocato, E.; Bruun, S. H.; Bulla, M.; Campana, S.; Cappellaro, E.; Castro-Tirado, A. J.; Chambers, K. C.; Chaty, S.; Chen, T-W; Ciolfi, R.; Coleiro, A.; Copperwheat, C. M.; Covino, S.; Cutter, R.; D'Ammando, F.; D'Avanzo, P.; De Cesare, G.; D'Elia, V; Della Valle, M.; Denneau, L.; De Pasquale, M.; Dhillon, V. S.; Dyer, M. J.; Elias-Rosa, N.; Evans, P. A.; Eyles-Ferris, R. A. J.; Fiore, A.; Fraser, M.; Fruchter, A. S.; Fynbo, J. P. U.; Galbany, L.; Gall, C.; Galloway, D. K.; Getman, F., I; Ghirlanda, G.; Gillanders, J. H.; Gomboc, A.; Gompertz, B. P.; Gonzalez-Fernandez, C.; Gonzalez-Gaitan, S.; Grado, A.; Greco, G.; Gromadzki, M.; Groot, P. J.; Gutierrez, C. P.; Heikkila, T.; Heintz, K. E.; Hjorth, J.; Hu, Y-D; Huber, M. E.; Inserra, C.; Izzo, L.; Japelj, J.; Jerkstrand, A.; Jin, Z. P.; Jonker, P. G.; Kankare, E.; Kann, D. A.; Kennedy, M.; Kim, S.; Klose, S.; Kool, E. C.; Kotak, R.; Kuncarayakti, H.; Lamb, G. P.; Leloudas, G.; Levan, A. J.; Longo, F.; Lowe, T. B.; Lyman, J. D.; Magnier, E.; Maguire, K.; Maiorano, E.; Mandel, I; Mapelli, M.; Mattila, S.; McBrien, O. R.; Melandri, A.; Michalowski, M. J.; Milvang-Jensen, B.; Moran, S.; Nicastro, L.; Nicholl, M.; Guelbenzu, A. Nicuesa; Nuttal, L.; Oates, S. R.; O'Brien, P. T.; Onori, F.; Palazzi, E.; Patricelli, B.; Perego, A.; Torres, M. A. P.; Perley, D. A.; Pian, E.; Pignata, G.; Piranomonte, S.; Poshyachinda, S.; Possenti, A.; Pumo, M. L.; Quirola-Vasquez, J.; Ragosta, F.; Ramsay, G.; Rau, A.; Rest, A.; Reynolds, T. M.; Rosetti, S. S.; Rossi, A.; Rosswog, S.; Sabha, N. B.; Carracedo, A. Sagues; Salafia, O. S.; Salmon, L.; Salvaterra, R.; Savaglio, S.; Sbordone, L.; Schady, P.; Schipani, P.; Schultz, A. S. B.; Schweyer, T.; Smartt, S. J.; Smith, K. W.; Smith, M.; Sollerman, J.; Srivastav, S.; Stanway, E. R.; Starling, R. L. C.; Steeghs, D.; Stratta, G.; Stubbs, C. W.; Tanvir, N. R.; Testa, V; Thrane, E.; Tonry, J. L.; Turatto, M.; Ulaczyk, K.; van der Horst, A. J.; Vergani, S. D.; Walton, N. A.; Watson, D.; Wiersema, K.; Wiik, K.; Wyrzykowski, L.; Yang, S.; Yi, S-X; Young, D. R.
    Context. Gravitational wave (GW) astronomy has rapidly reached maturity, becoming a fundamental observing window for modern astrophysics. The coalescences of a few tens of black hole (BH) binaries have been detected, while the number of events possibly including a neutron star (NS) is still limited to a few. On 2019 August 14, the LIGO and Virgo interferometers detected a high-significance event labelled S190814bv. A preliminary analysis of the GW data suggests that the event was likely due to the merger of a compact binary system formed by a BH and a NS.Aims. In this paper, we present our extensive search campaign aimed at uncovering the potential optical and near infrared electromagnetic counterpart of S190814bv. We found no convincing electromagnetic counterpart in our data. We therefore use our non-detection to place limits on the properties of the putative outflows that could have been produced by the binary during and after the merger.Methods. Thanks to the three-detector observation of S190814bv, and given the characteristics of the signal, the LIGO and Virgo Collaborations delivered a relatively narrow localisation in low latency - a 50% (90%) credible area of 5 deg(2) (23 deg(2)) - despite the relatively large distance of 26752 Mpc. ElectromagNetic counterparts of GRAvitational wave sources at the VEry Large Telescope collaboration members carried out an intensive multi-epoch, multi-instrument observational campaign to identify the possible optical and near infrared counterpart of the event. In addition, the ATLAS, GOTO, GRAWITA-VST, Pan-STARRS, and VINROUGE projects also carried out a search on this event. In this paper, we describe the combined observational campaign of these groups.Results. Our observations allow us to place limits on the presence of any counterpart and discuss the implications for the kilonova (KN), which was possibly generated by this NS-BH merger, and for the strategy of future searches. The typical depth of our wide-field observations, which cover most of the projected sky localisation probability (up to 99.8%, depending on the night and filter considered), is r similar to 22 (resp. K similar to 21) in the optical (resp. near infrared). We reach deeper limits in a subset of our galaxy-targeted observations, which cover a total similar to 50% of the galaxy-mass-weighted localisation probability. Altogether, our observations allow us to exclude a KN with large ejecta mass M greater than or similar to 0.1 M-circle dot to a high (> 90%) confidence, and we can exclude much smaller masses in a sub-sample of our observations. This disfavours the tidal disruption of the neutron star during the merger.Conclusions. Despite the sensitive instruments involved in the campaign, given the distance of S190814bv, we could not reach sufficiently deep limits to constrain a KN comparable in luminosity to AT 2017gfo on a large fraction of the localisation probability. This suggests that future (likely common) events at a few hundred megaparsecs will be detected only by large facilities with both a high sensitivity and large field of view. Galaxy-targeted observations can reach the needed depth over a relevant portion of the localisation probability with a smaller investment of resources, but the number of galaxies to be targeted in order to get a fairly complete coverage is large, even in the case of a localisation as good as that of this event.
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    Panning for gold, but finding helium: Discovery of the ultra-stripped supernova SN 2019wxt from gravitational-wave follow-up observations
    (2023) Agudo, I.; Amati, L.; An, T.; Bauer, F. E.; Benetti, S.; Bernardini, M. G.; Beswick, R.; Bhirombhakdi, K.; de Boer, T.; Branchesi, M.; Brennan, S. J.; Brocato, E.; Caballero-Garcia, M. D.; Cappellaro, E.; Castro Rodriguez, N.; Castro-Tirado, A. J.; Chambers, K. C.; Chassande-Mottin, E.; Chaty, S.; Chen, T. -W.; Coleiro, A.; Covino, S.; D'Ammando, F.; D'Avanzo, P.; D'Elia, V.; Fiore, A.; Floers, A.; Fraser, M.; Frey, S.; Frohmaier, C.; Fulton, M.; Galbany, L.; Gall, C.; Gao, H.; Garcia-Rojas, J.; Ghirlanda, G.; Giarratana, S.; Gillanders, J. H.; Giroletti, M.; Gompertz, B. P.; Gromadzki, M.; Heintz, K. E.; Hjorth, J.; Hu, Y. -D.; Huber, M. E.; Inkenhaag, A.; Izzo, L.; Jin, Z. P.; Jonker, P. G.; Kann, D. A.; Kool, E. C.; Kotak, R.; Leloudas, G.; Levan, A. J.; Lin, C. -C.; Lyman, J. D.; Magnier, E. A.; Maguire, K.; Mandel, I.; Marcote, B.; Sanchez, D. Mata; Mattila, S.; Melandri, A.; Michalowski, M. J.; Moldon, J.; Nicholl, M.; Guelbenzu, A. Nicuesa; Oates, S. R.; Onori, F.; Orienti, M.; Paladino, R.; Paragi, Z.; Perez-Torres, M.; Pian, E.; Pignata, G.; Piranomonte, S.; Quirola-Vasquez, J.; Ragosta, F.; Rau, A.; Ronchini, S.; Rossi, A.; Sanchez-Ramirez, R.; Salafia, O. S.; Schulze, S.; Smartt, S. J.; Smith, K. W.; Sollerman, J.; Srivastav, S.; Starling, R. L. C.; Steeghs, D.; Stevance, H. F.; Tanvir, N. R.; Testa, V.; Torres, M. A. P.; Valeev, A.; Vergani, S. D.; Vescovi, D.; Wainscost, R.; Watson, D.; Wiersema, K.; Wyrzykowski, L.; Yang, J.; Yang, S.; Young, D. R.
    We present the results from multi-wavelength observations of a transient discovered during an intensive follow-up campaign of S191213g, a gravitational wave (GW) event reported by the LIGO-Virgo Collaboration as a possible binary neutron star merger in a low latency search. This search yielded SN 2019wxt, a young transient in a galaxy whose sky position (in the 80% GW contour) and distance (similar to SIM;150 Mpc) were plausibly compatible with the localisation uncertainty of the GW event. Initially, the transient's tightly constrained age, its relatively faint peak magnitude (M-i similar to -16.7 mag), and the r-band decline rate of similar to 1 mag per 5 days appeared suggestive of a compact binary merger. However, SN 2019wxt spectroscopically resembled a type Ib supernova, and analysis of the optical-near-infrared evolution rapidly led to the conclusion that while it could not be associated with S191213g, it nevertheless represented an extreme outcome of stellar evolution. By modelling the light curve, we estimated an ejecta mass of only similar to 0.1 M circle dot, with Ni-56 comprising similar to 20% of this. We were broadly able to reproduce its spectral evolution with a composition dominated by helium and oxygen, with trace amounts of calcium. We considered various progenitor channels that could give rise to the observed properties of SN 2019wxt and concluded that an ultra-stripped origin in a binary system is the most likely explanation. Disentangling genuine electromagnetic counterparts to GW events from transients such as SN 2019wxt soon after discovery is challenging: in a bid to characterise this level of contamination, we estimated the rate of events with a volumetric rate density comparable to that of SN 2019wxt and found that around one such event per week can occur within the typical GW localisation area of O4 alerts out to a luminosity distance of 500 Mpc, beyond which it would become fainter than the typical depth of current electromagnetic follow-up campaigns.
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    Probing a magnetar origin for the population of extragalactic fast X-ray transients detected by Chandra
    (2024) Quirola-Vasquez, J.; Bauer, F. E.; Jonker, P. G.; Brandt, W. N.; Eappachen, D.; Levan, A. J.; Lopez, E.; Luo, B.; Ravasio, M. E.; Sun, H.; Xue, Y. Q.; Yang, G.; Zheng, X. C.
    Context. Twenty-two extragalactic fast X-ray transients (FXTs) have now been discovered from two decades of Chandra data (analyzing similar to 259 Ms of data), with 17 associated with distant galaxies (greater than or similar to 100 Mpc). Different mechanisms and progenitors have been proposed to explain their properties; nevertheless, after analyzing their timing, spectral parameters, host -galaxy properties, luminosity function, and volumetric rates, their nature remains uncertain. Aims. We interpret a sub -sample of nine FXTs that show a plateau or a fast -rise light curve within the framework of a binary neutron star (BNS) merger magnetar model. Methods. We fit their light curves and derive magnetar (magnetic field and initial rotational period) and ejecta (ejecta mass and opacity) parameters. This model predicts two zones: an orientation -dependent free zone (where the magnetar spin -down X-ray photons escape freely to the observer) and a trapped zone (where the X-ray photons are initially obscured and only escape freely once the ejecta material becomes optically thin). We argue that six FXTs show properties consistent with the free zone and three FXTs with the trapped zone. Results. This sub -sample of FXTs has a similar distribution of magnetic fields and initial rotation periods to those inferred for short gamma -ray bursts, suggesting a possible association. We compare the predicted ejecta emission fed by the magnetar emission (called merger -nova) to the optical and near -infrared upper limits of two FXTs, XRT 141001 and XRT 210423 where contemporaneous optical observations are available. The non -detections place lower limits on the redshifts of XRT 141001 and XRT 210423 of z greater than or similar to 1.5 and greater than or similar to 0.1, respectively. Conclusions. If the magnetar remnants lose energy via gravitational waves (GWs), it should be possible to detect similar objects with the current advanced LIGO detectors out to a redshift z less than or similar to 0.03, while future GW detectors will be able to detect them out to z approximate to 0.5.
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    Probing for the host galaxies of the fast X-ray transients XRT 000519 and XRT 110103
    (2022) Eappachen, D.; Jonker, P. G.; Fraser, M.; Torres, M. A. P.; Dhillon, V. S.; Marsh, T.; Littlefair, S. P.; Quirola-Vasquez, J.; Maguire, K.; Mata Sanchez, D.; Cannizzaro, G.; Kostrzewa-Rutkowska, Z.; Wevers, T.; Onori, F.; Inkenhaag, Anne; Brennan, S. J.
    Over the past few years, similar to 30 extragalactic fast X-ray transients (FXRTs) have been discovered, mainly in Chandra and XMM-Newton data. Their nature remains unclear, with proposed origins, including a double neutron star merger, a tidal disruption event involving an intermediate-mass black hole and a white dwarf, or a supernova shock breakout. A decisive differentiation between these three promising mechanisms for their origin requires an understanding of the FXRT energetics, environments, and/or host properties. We present optical observations obtained with the Very Large Telescope for the FXRTs XRT 000519 and XRT 110103 and Gran Telescopio Canarias observations for XRT 000519 designed to search for host galaxies of these FXRTs. In the g(s), r(s), and R-band images, we detect an extended source on the north-west side of the similar to 1 '' (68 per cent confidence) error circle of the X-ray position of XRT 000519 with a Kron magnitude of g(s) = 26.29 +/- 0.09 (AB magnitude). We discuss the XRT 000519 association with the probable host candidate for various possible distances, and we conclude that if XRT 000519 is associated with the host candidate a supernova shock breakout scenario is likely excluded. No host galaxy is found near XRT 110103 down to a limiting magnitude of R > 25.8.
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    The Fast X-Ray Transient XRT 210423 and Its Host Galaxy
    (2023) Eappachen, D.; Jonker, P. G.; Levan, A. J.; Quirola-Vasquez, J.; Torres, M. A. P.; Bauer, F. E.; Dhillon, V. S.; Marsh, T.; Littlefair, S. P.; Ravasio, M. E.; Fraser, M.
    Fast X-ray Transients (FXTs) are X-ray flares with durations ranging from a few hundred seconds to a few hours. Possible origins include the tidal disruption of a white dwarf by an intermediate-mass black hole, a supernova shock breakout, or a binary neutron star merger. We present the X-ray light curve and spectrum as well as deep optical imaging of the FXT XRT 210423, which has been suggested to be powered by a magnetar produced in a binary neutron star merger. Our Very Large Telescope and Gran Telescopio Canarias (GTC) observations began on 2021 May 6, thirteen days after the onset of the flare. No transient optical counterpart is found in the 1 (3s) X-ray uncertainty region of the source to a depth g(s) = 27.0 AB mag. (We use the word "counterpart" for any transient light in a wave band other than the original X-ray detection wave band, whereas the word "host" refers to the host galaxy.) A candidate host lies within the 1 X-ray uncertainty region with a magnitude of 25.9 +/- 0.1 in the GTC/ HiPERCAM g(s) filter. Due to its faintness, it was not detected in other bands, precluding a photometric redshift determination. We detect two additional candidate host galaxies: one with zspec = 1.5082 +/- 0.0001 and an offset of 4 2 +/- 1 (37 +/- 9 kpc) from the FXT, and another one with = z 1.04+ (+0.22)(-0.14) and an offset of 3."6 +/- 1." (30 +/- 8 kpc). Based on the properties of all the prospective hosts, we favor a binary neutron star merger, as previously suggested in the literature, as the explanation for XRT 210423.
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    The superluminous transient ASASSN-15lh as a tidal disruption event from a Kerr black hole.
    (2016) Leloudas, G.; Kim, Sam; Fraser, M.; Stone, N. C.; Velzen, S. van; Jonker, P. G.; Arcavi, I.; Fremling, C.; Maund, J. R.; Smartt, S. J.; Krühler, Thomas
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    The supermassive black hole coincident with the luminous transient ASASSN-15lh.
    (2017) Krühler, Thomas; Kim, Sam; Fraser, M.; Leloudas, G.; Schulze, Steve; Stone, N. C.; Velzen, S. van; Amorin, R.; Hjorth, J.; Jonker, P. G.; Kann, D. A.
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    XMM-Newton-discovered Fast X-ray Transients: host galaxies and limits on contemporaneous detections of optical counterparts
    (2024) Eappachen, D.; Jonker, P. G.; Quirola-Vasquez, J.; Mata Sanchez, D.; Inkenhaag, A.; Levan, A. J.; Fraser, M.; Torres, M. A. P.; Bauer, F. E.; Chrimes, A. A.; Stern, D.; Graham, M. J.; Smartt, S. J.; Smith, K. W.; Ravasio, M. E.; Zabludoff, A. I.; Yue, M.; Stoppa, F.; Malesani, D. B.; Stone, N. C.; Wen, S.
    Extragalactic fast X-ray transients (FXTs) are a class of soft (0.3-10 keV) X-ray transients lasting a few hundred seconds to several hours. Several progenitor mechanisms have been suggested to produce FXTs, including supernova shock breakouts, binary neutron star mergers, or tidal disruptions involving an intermediate-mass black hole and a white dwarf. We present detailed host studies, including spectroscopic observations of the host galaxies of seven XMM-Newton-discovered FXTs. The candidate hosts lie at redshifts 0.0928