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Spectral confirmation of galactic nova ASASSN-17hx (=ASASSN-17ib)

ATel #10527; A. Kurtenkov (Institute of Astronomy and NAO, Bulgaria), T. Tomov (Nicolaus Copernicus University, Torun, Poland), P. Pessev (GTC, IAC, ULL, Spain)
on 24 Jun 2017; 12:07 UT
Credential Certification: Kiril Stoyanov (kstoyanov@astro.bas.bg)

Subjects: Optical, Cataclysmic Variable, Nova

Referred to by ATel #: 10542, 10552, 10558, 10572, 10613, 10636, 10641, 10725, 10737

ASASSN-17hx (=ASASSN-17ib, ATel #10523, #10524, RA = 18:31:45.918, Dec = -14:18:55.57, J2000) was recently identified as a galactic nova candidate prior to its optical maximum. On 2017 Jun 24.0 UT we obtained three low-resolution spectra of the object with a 15 min exposure each. The observations were made with the FoReRo2 focal reducer mounted at the 2mRCC telescope at the Rozhen observatory in Bulgaria. Preliminary wavelength and relative flux calibrations were applied. The strongest emissions in the nova spectrum are H-alpha and H-beta. Other strong emissions are HeI (7065A, 6678A, 5876A, 5048A, 5011A, 4922A, 4713A), NII (6482A, 6346A, 5679A). This indicates that the nova is of He/N type, according to the Williams (1992, AJ, 104, 725) classification. Also present are the NIII 4640A and HeII 4686A emissions, with the NIII line being stronger.

The FWHM of the Balmer emissions is 1180+/-10 km/s and 1130+/-20 km/s for H-alpha and H-beta respectively, not accounted for the low spectral resolution (R=500). The strongest HeI lines show P Cyg profiles from which absorption components an expanding velocity of the order of 990+/-80 km/s can be estimated.

A combined spectrum can be previewed at: https://www.dropbox.com/s/2235tx1fqscwbeo/ASASSN-17hx_Rozhen_20170623.png?dl=0

A search in the GTC Public Archive, Gemini Science Archive, ESO Archive Facility and the Mikulski Archive for Space Telescopes (HST and Kepler) has not returned any observations on the transient position. The only counterpart identified through an extensive search of the available catalogs is Gaia Source ID 4104113350446549888, located 0.59" away from the reported transient position (also noted by the ASAS-SN team). Taking into account the Gaia estimate of Gmag=19.102, a lower limit for the brightness increase since quiescence can be set at A > 6.6 mag.

Further photometric and spectroscopic observations are strongly encouraged.