Two X-ray transients in M51
ATel #14220; Murray Brightman (Caltech), Hannah Earnshaw (Caltech), Dominic Walton (University of Cambridge), Tim Roberts (University of Durham)
on 25 Nov 2020; 23:38 UT
Credential Certification: Murray Brightman (murray@srl.caltech.edu)
Subjects: X-ray, Black Hole, Cataclysmic Variable, Neutron Star, Transient
We report on the detection of two X-ray transients in the M51 galaxies. These sources were detected by Chandra on 2020-11-18 in a 35-ks observation, and were not detected in a similar observation one month prior, nor in any of the numerous previous Chandra, XMM-Newton, or Swift observations. Both sources exhibit 0.5--8 keV luminosities of ~10^38 erg/s at an assumed distance of 8.58 Mpc to M51, and soft spectra (Gamma~4 or kT~0.6 keV). The positions of the sources also place them in or near catalogued star clusters. Their properties are consistent with X-ray binaries in outburst. Details below:
Source 1:
RA=202.4487 deg, Dec=47.183141 deg
NH=1.2^+1.2_-0.8x10^22 cm^-2, Gamma=4.2^+2.2_-1.7 or kT=0.6^+0.4_-0.2 keV
FX=1.6+/-0.4x10^-14 ergs/cm^2/s, LX=1.4+/-0.3x10^38 ergs/s
Source 2:
RA=202.4796 deg, Dec=47.260531 deg
NH=1.6^+2.9_-1.4x10^22 cm^-2, Gamma=4.0^+4.2_-2.2 or kT=0.6^+1.1_-0.3 keV
FX=8.5+/-2.8x10^-15 ergs/cm^2/s, LX=7.5+/-2.5x10^37 ergs/s
The Chandra observation in which these sources were detected is part of a year-long monitoring program of the galaxies, with a cadence of ~1 month (PI. Earnshaw). We will continue to post potential sources of interest here.
