The Suite of Strong Near Infrared Coronal Line Emission in nova V1674 Herculis
ATel #14765; C. E. Woodward (U. Minnesota), D. P.K. Banerjee (PRL, India), A. Evans (Keele U., UK), R. M. Wagner (Ohio State U.), S. Starrfield (Arizona State U.)
on 8 Jul 2021; 16:14 UT
Credential Certification: C.E. Woodward (chickw024@gmail.com)
Subjects: Infra-Red, Nova
We report 0.75 to 4.2 micron observations of the very fast nova V1674 Her (ATel #14740, #14737, #14736) obtained on 2021 July 7.279 UT with the 3.2-m NASA IRTF telescope using SpeX (Rayner et al. 2003, PASP 115, 362) in cross-dispersed mode (SXD and LXD) with an 0.5 arcsec slit (R = 1200) under photometric conditions and good seeing (0.7 arcsec in the K-band). The spectra show a marked evolution from our earlier observation on 2021 June 24.423 UT (ATel #14741) with coronal emission now dominating the near-infrared (NIR) region. HeI 1.083 micron continues to be the strongest line in the NIR, but lines of hydrogen and oxygen (OI 0.8446 and 1.1287 micron) are now considerably fainter than the coronal lines. Strong emission is seen in the lines of [Si X] 1.4305, [Si VI] 1.9650, [Al IX] 2.0400, [Si VII] 2.4833, [Al V] 2.911, [Mg VIII] 3.0325, [Al VI] 3.6597 + [Al VIII] 3.6900 (blended) and [Si IX] 3.9357 micron. Possibly also detected are [S IX] 1.2523, [Si IX] 1.5599, and [P VIII] 1.7361; the last two of these are blended with Brackett lines. The coronal lines show a flat top structure with sub-peaks, the most prominent of which is a sharp spike at the extreme blue edge of the profile top. The FWHM and FWZI of the [Si VII] 2.4833 and [Si IX] 3.9357 micron lines are in the range 6000 to 6150 km/s and 10500 to 11000 km/s respectively. Their measured fluxes are (single Gaussian-fit) are 1.5e-11 ergs/s/cm2 and 3.9e-12 erg/s/cm2 respectively in comparison with Br-alpha 4.052 micron which has a flux of 6.3e-13 erg/s/cm2. The nova has progressed rapidly to higher stages of ionization and further optical and infrared observations are warranted and encouraged.
These observations were conducted in part under IRTF program 2021A012, and the authors thank the NASA IRTF staff for their assistance.
