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V404 Cygni near-infrared photometry and spectroscopy

ATel #7760; A. A. Arkharov (Pulkovo Observatory), V. M. Larionov (St. Petersburg University and Pulkovo Observatory), A. Di Paola (INAF-Rome)
on 3 Jul 2015; 15:21 UT
Credential Certification: V. Larionov (vlar@astro.spbu.ru)

Subjects: Infra-Red, Black Hole, Transient

Referred to by ATel #: 7959

We perform monitoring of V404 Cyg using 1.1-m AZT-24 telescope at Campo Imperatore, Italy (near-infrared SWIRCAM camera) starting from 2015 June 25, when it was as bright as J=8.30. In the night of July 1 we got low-resolution (R=300) spectra in the range 0.8-2.3 mkm, showing hydrogen emission in Pashen and Brackett series. Total exposure time is 1300 sec for both of ZJ and HK grisms. Flux-calibrated spectrum is shown here . During the night of July 2 we performed dense intranight monitoring of V404 Cyg in J, H, K bands. The results are plotted, together with the whole light curve, here . It may be noticed that the amplitude of NIR intranight variability is substantially less than previously reported in R band (see, e.g. ATel #7729). It is not yet clear whether V404 Cyg calms down when becoming fainter or this is a manifestation of wavelength-dependent behavior.