black hole

Alert Notice 625: ASASSN-18ey = MAXI J1820+070 coverage needed for VLT and XMM

March 21, 2018: Dr. Tom Maccarone (Texas Tech University) has requested AAVSO observers' assistance in monitoring the outbursting black hole X-ray binary ASASSN-18ey = MAXI J1820+070 in support of VLT and XMM observations scheduled for:

2018 22 March 08-09:30 UT  and  29 March 08-09:30 UT

V time series are requested, with as short a cadence as possible (ideally, a time resolution of 0.1 second or better).

Alert Notice 592: V404 Cyg observations needed tonight for Chandra observations

August 11, 2017: Dr. Gregory Sivakoff (University of Alberta) and colleagues have requested AAVSO observers' assistance in observing the black hole X-ray transient LMXB V404 Cyg in support of Chandra observations taking place TONIGHT. The Chandra schedule is

2017 Aug 11 23:49:04.072  - 2017 Aug 12 13:42:14.730 UTC

Alert Notice 523: Correction to AAVSO Alert Notice 522

July 1, 2015:  In AAVSO Alert Notice 522 on the upcoming observations of the black hole X-ray binary V404 Cyg by HST, the date of the detection by the Swift satellite was incorrectly given as 2015 June 16.77197 UT (Barthelmy et al., GCN Circular 17929). The correct date is 2015 June 15.77197 UT.

Our sincere apologies for this error!

Alert Notice 397: Request for optical photometry of the bright X-ray binary V884 Sco (4U 1700-377)

June 30, 2009

Dr. Jerome Orosz (SDSU) has requested the assistance of southern bright star observers in observing the high-mass X-ray binary star V884 Sco (== 4U 1700-377). Orosz and collaborators are attempting to measure the mass of the compact object to clarify whether the object is a black hole or a neutron star. Optical photometry of the ellipsoidal variations of V884 Sco will be used in conjunction with optical spectroscopy to be performed at Las Campanas in mid-July and early August 2009 to measure the dynamical properties of the system.

Special Notice #253: Request for Observations of MAXI J1836-194

September 10, 2011: Dr. Gregory Sivakoff (U. of Alberta) requests observations of the X-ray binary star MAXI J1836-194 as part of the JACPOT collaboration studying stellar radio jets from compact binaries.  There is no predetermined duration for this campaign, but observations are requested now to coincide with ongoing X-ray and radio observations.