Near-infrared observations of Nova Sco 2014; a likely symbiotic nova.

ATel #6032; Vishal Joshi, D. P.K. Banerjee, V, Venkataraman, N. M. Ashok (Physical Research Laboratory, Ahmedabad, India)
on 31 Mar 2014; 17:46 UT
Credential Certification: Dipankar P.K. Banerjee (orion@prl.res.in)

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Near-IR photometry and spectroscopy of TCP J17154683-3128303 = Nova Scorpius 2014 was obtained on 2014 March 31 with the Mount Abu 1.2 meter telescope and the Near-Infrared Imager/Spectrograph (NICS) at R ~ 1000 in the 0.85-2.4 micron region. TCP J17154683-3128303 was first detected as a transient source by Nishiyama & Kabashima (CBAT Transient Object Follow-up Reports). Follow up optical spectra obtained by K. Ayani & S. Maeno (CBAT Transient Object Follow-up Reports) and Jelinek et al (ATEL #6025) suggested this object to be nova in the early phase and designated as Nova Scorpius 2014.

The NIR spectra, which are dominated by broad Hydrogen lines of the Paschen and Brackett series and strong HeI lines at 1.083 and and 2.058 (HeI 1.7002 is also seen), are typical of the He/N class of novae (Banerjee & Ashok 2012, BASI, 40, 243). The Lyman beta fluoresced OI 1.1287 line is also seen with significant strength. However, the most striking feature is the presence of first overtone absorption bands of CO at 2.29 microns and beyond. Such bands are similarly seen in other symbiotic systems such as V407 Cyg, RS Oph and V745 Sco but much later after their respective outbursts when the contribution from the M giant secondary becomes significant relative to the fading nova emission. From the above it would thus appear that Nova Sco is also a symbiotic system. It is also to be noted that there is a good positional co-incidence (less than 0.5 arc seconds in both RA and Dec) of the nova with the bright source 2MASS 17154687-3128303 (J = 11.255, H = 10.049, K= 9.578) suggesting that the 2MASS source is the likely progenitor star.

All emission lines are broad. The H and He lines show a reasonably rectangular shape, often seen in He/N novae, but with the profile tops having considerable structures most pronounced of which is a sharp narrow central component in emission. This narrow component could likely emanate from the secondary giant's wind. The OI 1.1287 line lacks this narrow emission component. The FWZI's of Pa beta, Br Gamma, HeI (2.057micron) and OI (1.1287 micron) are 8900, 9500, 10100, 8800 km/s respectively. Photometry on 2014 March 29 shows the source to have NIR magnitudes of J = 8.80 +- 0.03, H = 8.31 +- 0.04 and K = 7.62 +- 0.02.

It is very desirable to follow this object at other wavelengths especially in hard X-rays and gamma-rays to detect and track the evolution of highly heated, shocked gas created as a consequence of the propagation of the nova's ejecta into an ambient red giant wind (in case the 2MASS source is indeed the secondary companion). X-ray emission from the Swift XRT-PC (0.3-10 keV) has been already detected from the source on March 27 (ATel #6015) and modeled to represent a temperature of kT ~ 6.4 keV.