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First overtone CO detected in emission in Galactic nova TCP J17394608-2457555

ATel #10369; Vishal Joshi and Dipankar P. K. Banerjee, (Physical Research Laboratory, Ahmedabad, India)
on 12 May 2017; 02:33 UT
Credential Certification: Vishal Joshi (vjoshi@prl.res.in)

Subjects: Infra-Red, Cataclysmic Variable, Nova

Referred to by ATel #: 10399, 10420, 10492, 10536

We report near-infrared spectroscopy on 2017 May 11.9375 UT of the Galactic nova TCP J17394608-2457555 (CBAT; ATel #10366, ATel #10367) from the Mount Abu 1.2m telescope using the Near-Infrared Camera/Spectrograph (NICS). Spectra were obtained in the 0.85 to 2.4 micron range at a resolution of ~1000. The spectra are typical of the Fe II class of novae, NIR templates of which are given for several novae in Banerjee & Ashok 2012, BASI, 40, 243. The observed emission lines include strong Hydrogen lines of the Paschen and Brackett series, several strong CI lines and prominent Lyman beta fluoresced OI 1.1287. The HeI 1.083 micron line is weak but clearly present. The Paschen beta 1.2818 micron line has an FWHM velocity of ~1600 km/s while the FWZI velocity is ~ 2500 km/s. However, the significant finding is the detection of strong first overtone CO emission bands in the K band. The first four bandheads from (2-0) to (5-3) are recorded in our spectrum (occuring at 2.2935, 2.3227, 2.3535 and 2.3829 microns respectively). The known instances of first overtone CO detection in novae are few (about 10) and all such novae have proceeded to produce significant dust. Dust formation in this nova is therefore very likely and further monitoring is desirable. NIR photometry gives the following magnitudes: J = 9.87 +- 0.03, H = 9.16 +- 0.03, Ks = 8.56 +- 0.05.