TY - JOUR
T1 - Searching for fast extragalactic X-ray transients in Chandra surveys
AU - Yang, G.
AU - Brandt, W. N.
AU - Zhu, S. F.
AU - Bauer, F. E.
AU - Luo, B.
AU - Xue, Y. Q.
AU - Zheng, X. C.
N1 - Funding Information:
GY, WNB, and SFZ acknowledge support from CXC grant AR8-19016X, CXC grant AR8- 19011X, and NASA ADP grant 80NSSC18K0878. FEB acknowledges support from CONICYT-Chile (Basal AFB-170002, FONDO ALMA31160033) and the Ministry of Economy,Development, and Tourism's Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics, MAS. YQX acknowledges support from the 973 Program (2015CB857004), NSFC (11890693, 11421303), and the CAS Frontier Science Key Research Program (QYZDJ-SSW-SLH006).
Funding Information:
We thank the referee for helpful feedback that improved this work. We thank David Burrows, Qingling Ni, John Timlin, and Fabio Vito for helpful discussions. GY, WNB, and SFZ acknowledge support from CXC grant AR8-19016X, CXC grant AR8-19011X, and NASA ADP grant 80NSSC18K0878. FEB acknowledges support from CONICYT-Chile (Basal AFB-170002, FONDO ALMA 31160033) and the Ministry of Economy, Development, and Tourism’s Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics, MAS. YQX acknowledges support from the 973 Program (2015CB857004), NSFC (11890693, 11421303), and the CAS Frontier Science Key Research Program (QYZDJ-SSW-SLH006). The Guaranteed Time Observations (GTO) for the CDF-N included here were selected by the ACIS Instrument Principal Investigator, Gordon P. Garmire, currently of the Huntingdon Institute for X-ray Astronomy, LLC, which is under contract to the Smithsonian Astrophysical Observatory; Contract SV2-82024. This project uses Astropy (a Python package; see Astropy Collaboration 2018).
Publisher Copyright:
© 2019 The Author(s).
PY - 2019/6/25
Y1 - 2019/6/25
N2 - Recent works have discovered two fast (≈10 ks) extragalactic X-ray transients in the Chandra Deep Field-South (CDF-S XT1 and XT2). These findings suggest that a large population of similar extragalactic transients might exist in archival X-ray observations. We develop a method that can effectively detect such transients in a single Chandra exposure, and systematically apply it to Chandra surveys of CDF-S, CDF-N, DEEP2, UDS, COSMOS, and E-CDF-S, totaling 19 Ms of exposure. We find 13 transient candidates, including CDF-S XT1 and XT2. With the aid of available excellent multiwavelength observations, we identify the physical nature of all these candidates. Aside from CDF-S XT1 and XT2, the other 11 sources are all stellar objects, and all of them have z-band magnitudes brighter than 20. We estimate an event rate of {59+77-38} for CDF-S XT-like transients with 0.5-7 keV peak fluxes log Fpeak -12.6 (erg cm-2 s-1). This event rate translates to {15+20-10} transients existing among Chandra archival observations at Galactic latitudes |b| > 20°, which can be probed in future work. Future missions such as Athena and the Einstein Probe with large grasps (effective area × field of view) are needed to discover a large sample (∼thousands) of fast extragalactic X-ray transients.
AB - Recent works have discovered two fast (≈10 ks) extragalactic X-ray transients in the Chandra Deep Field-South (CDF-S XT1 and XT2). These findings suggest that a large population of similar extragalactic transients might exist in archival X-ray observations. We develop a method that can effectively detect such transients in a single Chandra exposure, and systematically apply it to Chandra surveys of CDF-S, CDF-N, DEEP2, UDS, COSMOS, and E-CDF-S, totaling 19 Ms of exposure. We find 13 transient candidates, including CDF-S XT1 and XT2. With the aid of available excellent multiwavelength observations, we identify the physical nature of all these candidates. Aside from CDF-S XT1 and XT2, the other 11 sources are all stellar objects, and all of them have z-band magnitudes brighter than 20. We estimate an event rate of {59+77-38} for CDF-S XT-like transients with 0.5-7 keV peak fluxes log Fpeak -12.6 (erg cm-2 s-1). This event rate translates to {15+20-10} transients existing among Chandra archival observations at Galactic latitudes |b| > 20°, which can be probed in future work. Future missions such as Athena and the Einstein Probe with large grasps (effective area × field of view) are needed to discover a large sample (∼thousands) of fast extragalactic X-ray transients.
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U2 - 10.1093/mnras/stz1605
DO - 10.1093/mnras/stz1605
M3 - Article
AN - SCOPUS:85070063076
VL - 487
SP - 4721
EP - 4736
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
SN - 0035-8711
IS - 4
ER -