The changing-type Seyfert NGC 2617 remains in a high state

ATel #9015; V. L. Oknyansky (Sternberg Astronomical Institute, Moscow), N. A. Huseynov (Shamakhy Astrophysical Observatory, Azerbaijan), B. P. Artamonov, V. M. Lipunov, E. S. Gorbovskoy, A. S. Kuznetsov, P. V. Balanutza, A. M. Tatarnikov, V. I. Metlov, N. I. Shatsky, A. E. Nadzhip, M. A. Burlak (Sternberg Astronomical Institute, Moscow), Kh. M. Mikailov, I. R. Salmanov (Shamakhy Astrophysical Observatory, Azerbaijan), C. M. Gaskell (UCSC)
on 1 May 2016; 08:18 UT
Credential Certification: Martin Gaskell (mgaskell@ucsc.edu)

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NGC 2617 was observed to undergo a dramatic change from a largely obscured Seyfert 1.8 to an unobscured Seyfert 1 between 2003 to 2013 (Shappee et al. 2013, ATel #5010; Shappee et al. 2014). We have been carrying out spectroscopic and BVRIJHK photometric monitoring of NGC 2617 from Jan 2016. We find that it remains in high state and can still be classified as a Seyfert 1. We have observed further variations in the optical and IR continuum levels, and also in the intensities and profiles of the Balmer lines. An optical light curve for 2010 - 2016 from the MASTER Global Robotic Network suggests that the dramatic Seyfert type change was not connected with the brightening observed at 2013 but probably happened between Oct 2010 and Feb 2012.

We have obtained JHK photometry with the new 2.5-m telescope of the SAI Caucasus Mountain Observatory using the ASTRONIRCAM operating in the JHK bands during Jan to Apr 2016. The light curve for a 5-arcsecond aperture can be seen here. Cross-correlation analysis shows that K-band variations lag J-band variability by 18 +/- 2 days. This is twice what we find from the Shappee at al. (2014) IR data for 2013. If the change in lag is real, it could be explained by sublimation of the some of the dust over the past three years.

We also obtained optical spectra covering the range 4100-7000 Angs. at a resolution of 3 - 7 Angs. using the 2x2 prism spectrograph on the 2-m Zeiss telescope of Shamakhy Astrophysical Observatory (ShAO) on Feb 3 & 4, Mar 4, and Apr 9 2016. Examples of mean spectra in the Hβ region for two of these nights compared with a spectrum from Shappee et al. (2013) can be seen here. Our new spectra show an emission component in the red wing of Hβ (with a shift of about +2500 km/s) which was absent in spectra obtained at 2013. This component is also present in the profile of Hγ in our spectra.

We obtained BVRI CCD photometry with the 50-cm Maksutov AZT-5 telescope of SAI Crimean Station and the Zeiss-600 telescope of ShAO on 10 nights in Mar.-Apr. 2016. The B light curve can be seen here. Magnitudes were measured with a 10-arcsecond aperture. The ShAO points are shown as open circles. NGC 2617 has brightened from B = 15.1 to 14.8 during the month of March and then decreased to B = 14.99 over the next three weeks. The amplitude of variability in the V band was about half the variability in the B band.

We also present here an unfiltered CCD white light curve for 2010 - 2016 from the MASTER Global Robotic Network. Relative magnitudes are given compared with two nearby comparison stars. Magnitudes were measured with a 15-arcsecond aperture (8 pixels). There were about 100 observations over a total of 19 nights. Each point represents the mean of all observations per night. The variations are similar to those found by Shappee et al. (2013) for 2012-2013. The interesting thing is that NGC 2617 now has about the same brightness as in 2012 and now has the spectrum of a typical Seyfert 1. We therefore suggest that the dramatic change in Seyfert type of NGC 2617 was not connected with the brightening observed in 2013 but probably happened between October 2010 and February 2012.

We are grateful to B. Shappee for sending us data in digital form. This work has been supported in part by M. V. Lomonosov Moscow State University Development Program. We thank the SAI director, A.M. Cherepashchuk, and the ShAO director, N. S. Jalilov, for granting us directors’ discretionary time. We also wish to express our appreciation to the staffs of the observatories for their support.