The Swift Bulge Survey: Motivation, Strategy, and First X-ray Results
A. Bahramian, C. O. Heinke, J. A. Kennea, T. J. Maccarone, P. A., Evans, R. Wijnands, N. Degenaar, J. J. M. in't Zand, A. W. Shaw, L. E. Rivera, Sandoval, S. McClure, A. J. Tetarenko, J. Strader, E. Kuulkers, G. R., Sivakoff

TL;DR
This survey used Swift to observe the Galactic Bulge, detecting 91 X-ray sources, including new VFXT candidates and insights into their nature, especially the prominence of symbiotic systems among VFXTs.
Contribution
First large-scale Swift survey of the Galactic Bulge focusing on VFXTs, providing new detections, classifications, and population constraints.
Findings
Detected 91 X-ray sources, 25 varied significantly
Identified 7 new hard transient VFXT candidates
Provided evidence for symbiotic systems as a major VFXT class
Abstract
Very faint X-ray transients (VFXTs) are X-ray transients with peak X-ray luminosities () of erg/s, which are not well-understood. We carried out a survey of 16 square degrees of the Galactic Bulge with the Swift Observatory, using short (60 s) exposures, and returning every 2 weeks for 19 epochs in 2017-18 (with a gap from November 2017 to February 2018, when the Bulge was in sun-constraint). Our main goal was to detect and study VFXT behaviour in the Galactic Bulge across various classes of X-ray sources. In this work, we explain the observing strategy of the survey, compare our results with the expected number of source detections per class, and discuss the constraints from our survey on the Galactic VFXT population. We detected 91 X-ray sources, 25 of which have clearly varied by a factor of at least 10. 45 of these X-ray sources have known counterparts: 17…
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