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THE ASTRONOMER Electronic Circular No 3131      2015 Dec 24 10.57UT
Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise,  Basingstoke,
Hants, RG22 4PP,England.Telephone/FAX(01256)471074Int:+441256471074
INTERNET: GUY@TAHQ.DEMON.CO.UK      Backup: gmh@wdcc1.bnsc.rl.ac.uk
WORLD WIDE WEB                         http://www.theastronomer.org
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V404 CYG OUTBURST
Mariko Kimura reports on VSNET that V404 Cyg, an X-ray transient, underwent
an outburst in 2015 June (see TA E-Circular 3084) but now in outburst again!

According to #ATel 8453, MASTER-Amur started observations of this object at
2015-12-23 09:14:02 UT.  At that stage its unfiltered magnitude was about
16.  This magnitude is almost the same as that on the initial stage of the
June outburst (BAAVSS alert 4101).

V404 Cyg was triggered by the Fermi Gamma Ray Burst Monitor (GBM) on
2015-Dec-21 at 17:30:50.36 (ATel #8457).  They reported that the current
activity of V404 Cyg was similar to the initial trigger on 2015-June-15.

On 2015-Dec-23 at 05:19:52 UT, the Swift Burst Alert Telescope (BAT) also
triggered it (ATel #8455). In addition, INTEGRAL IBIS/ISGRI confirmed its
renewed activity from the public observation between 2015-12-21 16:20 and
2015-12-23 04:21 UTC (ATel #8458).

It is well worth observing this outburst of V404 Cyg in optical bands
although development is uncertain. This object is highly reddened, and it
would be recommended to use filters (if possible) and multicolour
observations.

Guy M Hurst