학술논문
XMM-Newton-discovered Fast X-ray Transients: Host galaxies and limits on contemporaneous detections of optical counterparts
Document Type
Working Paper
Author
Eappachen, D.; Jonker, P. G.; Quirola-Vásquez, J.; Sánchez, D. Mata; 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.
Source
Subject
Language
Abstract
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 7 XMM-Newton-discovered FXTs. The candidate hosts lie at redshifts 0.0928 $< z <$ 0.645 implying peak X-ray luminosities of 10$^{43}$ erg s$^{-1}$ $< L_X <$ 10$^{45}$ erg s$^{-1}$,and physical offsets of 1 kpc < $r_\mathrm{proj}$ < 22 kpc. These observations increase the number of FXTs with a spectroscopic redshift measurement by a factor of 2, although we note that one event is re-identified as a Galactic flare star. We infer host star formation rates and stellar masses by fitting the combined spectroscopic and archival photometric data. We also report on a contemporaneous optical counterpart search to the FXTs in Pan-STARRS and ATLAS by performing forced photometry at the position of the FXTs. We do not find any counterpart in our search. Given our constraints, including peak X-ray luminosities, optical limits, and host properties, we find that XRT 110621 is consistent with a SN SBO event. Spectroscopic redshifts of likely host galaxies for four events imply peak X-ray luminosities that are too high to be consistent with SN SBOs, but we are unable to discard either the BNS or WD-IMBH TDE scenarios for these FXTs.
Comment: 17 pages, 10 figures, 6 tables. Accepted for publication in MNRAS
Comment: 17 pages, 10 figures, 6 tables. Accepted for publication in MNRAS