Optical Spectroscopy of V404 Cyg During the Recent X-ray and Optical Activity

ATel #7655; R. M. Wagner (LBTO/OSU), C. E. Woodward (Minnesota), S. Starrfield (ASU)
on 18 Jun 2015; 01:59 UT
Credential Certification: R. Mark Wagner (rmw@as.arizona.edu)

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After recent announcements of activity at both X-ray and optical wavelengths associated with the low mass X-ray binary and black hole V404 Cyg (GCN #17929, GCN #17931, GCN #17933, GCN #17938, ATEL #7646, ATEL #7647, GCN #17940, ATEL #7650, and GCN #17944), we obtained an optical spectrum (range 394-710 nm; resolution 0.38 nm) on 2015 June 17.414 UT with the 6.5 m MMT (+Blue Channel Spectrograph) on Mount Hopkins, Arizona. The spectrum exhibits strong emission lines of Hα, Hβ, Hγ, Hδ, and Hε; He I 706.5, 667.8, 587.5, 501.5, and 492.1 nm; He II 468.6 nm; and a broad but weaker feature centered at 463.4 nm associated with the C III/N III blend. The emission lines are superposed on a reddened continuum. The FWHM of Hα emission is 868 km/s. A comparison of this spectrum with one obtained on 1989 May 27 UT during the 1989 outburst are similar. However, we find that the observed He II/Hβ intensity ratio is ~0.33 now compared to ~1 in at the start of the 1989 outburst. The equivalent with of Hα emission in our MMT spectrum is about 7.3 nm compared to 2.2 nm measured in the 1989 May 27 UT spectrum. Further optical spectroscopy is encouraged.