Cygnus X-1 has returned to soft state
ATel #6344; V. Grinberg (MIT), J. Wilms (Remeis/ECAP/FAU), K. Pottschmidt (CRESST/GSFC, UMBC), M. Nowak (MIT), G. G. Pooley (MRAO), N. Hell (Remeis/ECAP/FAU, LLNL), J. Tomsick (SSL/UCB), P. Uttley (UvA), J. Rodriguez (CEA)
on 25 Jul 2014; 21:51 UT
Credential Certification: Victoria Grinberg (grinberg@space.mit.edu)
Subjects: Radio, X-ray, Binary, Black Hole
After the hardening of Cyg X-1 earlier this year (ATels #5995, #6021, #6115, #6119) and the recent softening (Atel #6244), both MAXI and Swift-BAT show that the source is now back in the soft state based on the criteria of Grinberg et al. 2013 (A&A 554, A88). Note that MAXI coverage resumed ~10 dayes ago and the source has been continually in a soft state since then.
The AMI-measured radio (15GHz) flux has been low (<5mJy) for the last ~7 days, confirming the soft state.
We recommend further monitoring of the source.
MAXI HIDs and BAT lightcurve plots used in this analysis are available at:
http://www.sternwarte.uni-erlangen.de/~grinberg/perm/201407_atel_maxi_hid.pdf
http://www.sternwarte.uni-erlangen.de/~grinberg/perm/201407_atel_bat_lc.pdf