Infrared spectroscopy reveals coronal line emission in the galactic nova V659 Sct

ATel #13815; C. E. Woodward (University of Minnesota, USA), D. P.K. Banerjee (PRL, India), A. Evans (Keele University, UK)
on 18 Jun 2020; 14:19 UT
Credential Certification: C.E. Woodward (chickw024@gmail.com)

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V659 Scuti (equivalently Nova Scuti 2019 / AT2019tpb / ASASSN-19aad) was discovered on 2019 October 29.05 UT and was suggested to be a He/N-type galactic nova (ATel #13252) based possibly on Helium lines seen in its spectrum early after its eruption (ATel #13241, ATel #13245). The nova was marginally detected in x-rays shortly after discovery (ATel #13252). Here we report 0.7-2.5 micron spectroscopic observations obtained on 2020 June 06.44 UT (day 221.4) with the NASA IRTF 3.2-m telescope and infrared spectrograph SpeX (Rayner et al. 2003, PASP 115, 362) using a 0.5 arcsec x 15 arcsec slit in the SXD (short-cross dispersed) mode (R =1200).

The spectrum is rich with emission lines. The Hydrogen lines of the Paschen (Pa13 though Pa6) and Brackett (Br15 through Br4) are detected as well as several lines of He I, He II, Oxygen (OI 0.8446, 1.3164 micron) and other atomic species. P-Cygni features are not present. The He I 1.0830 micron line is the strongest line in the spectrum, with a peak-to-continuum ratio of ~70 and an integrated flux density of ~1.08e-11 ergs/s/cm2. Strong infrared coronal line emission (e.g., Greenhouse et al. 1990, ApJ 352, 307) is seen from [Si VI] 1.9634 micron, [Ca VII] 2.3205 micron and [Si VII] 2.4834. We tentatively identify a few other weaker coronal lines viz. [Ar IV] 0.7237 micron, [Fe IX] 0.7892 micron, [Ti VI] 1.7156 micron, [Al IX] 2.0440 micron and a feature at ~2.1 micron which could possibly be [Mn XIV] 2.092 micron (based on measured wavelength centroids). The Si and Ca coronal emission profiles are double-peaked, with a deep dip between the blue and red peaks which are separated by 1500 to 1600 km/s. Based on the spectral shape of the observed continuum, dust formation has not occurred. Further observations of this nova, now in the nebular phase, are encouraged.

These observations were conducted under the IRTF program 2020A010 and we acknowledge partial support from NASA grant 80NSSC19K0868.