Observation of V404 Cyg in quiescence in 2015 November
ATel #8466; John A. Tomsick (SSL/UCB), Dom Walton (JPL/Caltech), Maica Clavel (SSL/UCB), George Lansbury (Univ. of Durham), and Daniel Stern (JPL)
on 27 Dec 2015; 01:06 UT
Credential Certification: John A. Tomsick (jtomsick@ssl.berkeley.edu)
Subjects: X-ray, Binary, Black Hole, Transient
As part of a program to follow-up serendipitous NuSTAR sources near primary NuSTAR targets (e.g., Aird et al. 2015), we obtained an observation of 3XMM J202421.7+335050 with the Chandra X-ray Observatory (ObsID 17245). The field of view included the black hole transient V404 Cyg, which was reported to have started a new outburst on 2015 December 23 (GCN Circ. 18716; ATEL#8455). The Chandra/ACIS observation had an exposure time of 14 ks and started on 2015 November 27, 3.26 h UT. The 0.3-10 keV spectrum is consistent with an absorbed power-law with nH = (1.1+/-0.3)e22 cm-2 (using Wilms et al. 2000 abundances), Gamma = 2.0+/-0.3 (90% confidence errors), and an absorbed 0.3-10 keV (3-10 keV) flux of 7.6e-13 (4.8e-13) erg/cm2/s. The Chandra/ACIS light curve shows strong variability with count rates ranging from <0.01 to 0.16+/-0.03 c/s in 200 sec time bins. The spectral and timing properties are typical for V404 Cyg in quiescence (see, e.g., Rana et al., arXiv:150704049), and show that the average flux increased by a factor of between 20 (based on the flux reported in ATEL#8462) and 50 (based on ATEL#8455) between November 27 and December 23.