IRTF SpeX Near-infrared Spectroscopy of the galactic nova N Sgr 2020 No. 2
ATel #13801; C. E. Woodward (University of Minnesota), D. P.K. Banerjee (PRL, India), A. Evans (Keele University), S. Starrfield (Arizona State University), R. M. Wagner (The Ohio State University)
on 12 Jun 2020; 13:08 UT
Credential Certification: C.E. Woodward (chickw024@gmail.com)
Subjects: Infra-Red, Nova
We report 0.7-4.2 micron near-infrared spectroscopic observations of the reddened
galactic nova N Sgr 2020 No. 2 (equivalently ASASSN-20ga/PGIR20dsv/ZTF20abdpwst/
AT 2020lrv; ATel #13790) obtained on 2020 June 11.4 UT with the infrared spectrograph
SpeX (Rayner et al. 2003, PASP 115, 362) using a 0.5 arcsec x 15 arcsec slit in both
SXD (short-cross dispersed) and LXD (long-short cross-dispersed) modes (R = 1200) on
the NASA IRTF 3.2-m telescope under good seeing conditions (0.67 arcsec in the K-band).
The spectrum resembles that of a nova close to maximum or possibly still on the
rise to maximum as the AAVSO light curve suggests (the unfiltered w/V zero point
data has shown a steady brightening from 14.3 to 13.2 magnitudes between 8 to 11 June 2020).
The numerous lines seen in the infrared are all either in absorption or more commonly
exhibit P-Cygni type line profiles. The Hydrogen lines of the Paschen, Brackett, Pfund,
and Humphreys series are dominant. Numerous neutral Carbon lines are seen which
clearly establish that this is a Fe II nova (Banerjee and Ashok 2012, BASI 40, 243). The
other standard lines of O and N that are expected in the spectra of the Fe II class of
novae are all present (e.g., O I 0.8446, 1.1287 and 1.3164 microns, N I 1.2461 and 1.2469
micron). He I lines are not seen.
The P-Cygni absorption minima are typically separated by ~ 370 km/s from the emission
for the H lines. The FWHMs of the Paschen and Brackett lines ranges from 400 to 450 km/s.
The emission line flux density of hydrogen Paschen-beta (1.282 micron) is ~ 5.6e-13 ergs/s/cm2,
while that of the Brackett-alpha (4.052 micron) line is ~ 1.3e-15 ergs/s/cm2.
We do not think that CO is present in emission though the region of the first overtone
bandheads (2.29 to 2.5 microns) is contaminated with two carbon lines and also Pfund series
lines, some of which are closely coincident in wavelength with the CO bandhead positions.
Further monitoring of this spectral region is desirable. No evidence for dust condensation at
this epoch was apparent given the spectral shape of the thermal continuum at wavelengths
greater than 3.0 micron. Further observations are encouraged.
These observations were conducted under IRTF program 2020A001, and we thank
Dave Griep (U. Hawaii, IFA) for the assistance with these remote observations. CEW acknowledges
partial support from NASA grant 80NSSC19K0868.