A New Sample of Transient Ultraluminous X-Ray Sources Serendipitously Discovered by Swift/XRT
Journal
Date Issued
2023
Author(s)
Brightman, Murray
•
Hameury, Jean-Marie
•
Lasota, Jean-Pierre
•
•
•
Cann, Jenna M.
•
Earnshaw, Hannah
•
Fürst, Felix
•
Heida, Marianne
•
Jaodand, Amruta
•
Lazzarini, Margaret
•
Middleton, Matthew J.
•
Walton, Dominic J.
•
Weaver, Kimberly A.
Abstract
Ultraluminous X-ray sources (ULXs) are our best laboratories for studying extreme super-Eddington accretion. Most studies of these objects are of relatively persistent sources; however, there is growing evidence to suggest a large fraction of these sources are transient. Here we present a sample of five newly reported transient ULXs in the galaxies NGC 4945, NGC 7793, and M81 serendipitously discovered in Swift/XRT observations. Swift monitoring of these sources have provided well-sampled lightcurves, allowing for us to model the lightcurves with the disk-instability model of Hameury & Lasota, which implies durations of 60-400 days and that the mass-accretion rate through the disk is close to or greater than the Eddington rate. Of the three source regions with prior Hubble Space Telescope imaging, color-magnitude diagrams of the potential stellar counterparts show varying ages of the possible stellar counterparts. Our estimation of the rates of these sources in these three galaxies is 0.4-1.3 yr−1. We find that, while persistent ULXs dominate the high end of galaxy luminosity functions, the number of systems that produce ULX luminosities are likely dominated by transient sources.
Volume
951
Issue
1
Start page
51
Issn Identifier
0004-637X
Rights
open.access
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