X-ray nova and LMXB V404 Cyg in rare outburst
AAVSO Alert Notice 520June 18, 2015X-ray nova and LMXB V404 Cyg in rare outburst
V404 Cyg, an X-ray nova and a low mass X-ray binary(LMXB) with black hole component, is undergoing its first reported X-ray andoptical outburst since 1989. Large scale, rapid variations are being reportedin wavelengths from X-ray to radio by professional and amateur astronomersworldwide.
Satellite and ground-based observations have been and arecontinuing to be made by the professional community, including:S. D. Barthelmy et al. (GCN Circular 17929, 15 June 2015,Swift BAT initial detection); H. Negoro et al. (ATel #7646, 17 Jun 2015); E.Kuulkers et al. (ATel #7647, 17 June 2015, Swift observations); K. Gazeas etal. (ATel #7650, 17 June 2015, optical photometry); R. M. Wagner et al. (ATel#7655, 18 June, optical spectroscopy); K. Mooley et al. (ATel #7658,18 June, radio observations); T. Munoz-Dariaset al. (ATel #7659, 18 Jun 2015, P Cyg profiles seen). They note that P-Cygprofiles were also observed during the1989 outburst (Casares et al. 1991, MNRAS, 250, 712), andthat V404 Cyg is so far the only black hole X-ray transient that has shown thisphenomenology.
Observations in all bands are requested. Filteredobservations are preferred. Please use a cadence as high as possible whileobtaining a suitable s/n. If spectroscopy is possible with your equipment, itis requested.
In the AAVSO International Database (AID), V-band datafrom D. Barrett (St. Leger Bridereix, France) on June 16.91-17.12(JD2457190.416111-.617176) show increasingly faintervariations V=12.95- 16.308. Rc-band data from C. Littlefield (Middletown, CT)on June17.13-.31 (JD 2457190.62715-.81017) show rapid variationsRc=13.534- 15.705. Ic-band data from Barrett on June 17.92-18.12 (JD2457191.420822-.623507) show rapid variationsIc=11.702-14.418. Other AID data include June 15.94787 UT, <14.1 visual (E.Muyllaert, Oostende, Belgium); 16.16875 UT, 16.18 V +/-0.035 (Muyllaert, CCD);16.978 UT, 13.8 visual (P. Schmeer, Bischmisheim,Germany); 17.02653,14.98 V +/-0.06 (S. O'Connor, St. George, Bermuda).
In the 1989 outburst, which was detected by Ginga on May22 (F. Makino et al. IAUC. #4782), V404 Cyg remained brighterthan visual magnitude 15.3 for at least 37 days. The AID shows a maximum visualmagnitude of 14.0 on 1989 June 3.021 UT (JD 2447680.521; S. Korth, Germany);the last positive observation was 15.3 on 1989 July 10.2 (2447717.7; C. Scovil,Stamford, CT).
Coordinates: 20 24 03.83 +33 52 02.2 (J2000.0)
Charts with comparison star sequence for V404 Cyg may becreated using the AAVSO Variable Star Plotter (VSP, http::www.aavso.org/vsp).A photometry table containing multicolor magnitudes ofcomparison stars may also be obtained via VSP.
Please report observations to the AAVSO InternationalDatabase using the name V404 CYG. Be sure to include error values andcomparison star information.
This AAVSO Alert Notice was compiled by Elizabeth O.Waagen.
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