The Mid-IR SOFIA FORCAST Spectrum of Nova V1405 Cassiopeia
ATel #14794; R. D. Gehrz (U. Minnesota), D. P. K. Banerjee (PRL, India), A. Evans (Keele U., UK), N. Karnath (USRA SOFIA), S. Starrfield (Arizona State U.), W. D. Vacca (USRA SOFIA), R. M. Wagner (Ohio State U.), C. E. Woodward (U. Minnesota)
on 17 Jul 2021; 21:48 UT
Credential Certification: Robert Gehrz (gehrz@astro.umn.edu)
Subjects: Infra-Red, Nova
We report 4.9 to 27.7 micron grism spectroscopy of the very slow, bright nova V1405 Cas (ATel #14471, #14472, #14478, #14482, #14530, #14614) obtained on 2021 July 01, 02, and 07 UT with the FORCAST (Herter, T. L., et al. 2012, ApJ, 749, L18) science instrument on the NASA Stratospheric Observatory for Infrared Astronomy (SOFIA; Young, E. T., et al., 2012, ApJ, 749, L17) 2.5-m telescope. The observations were made with a 4.7â wide slit using FORCAST grisms G063 covering 4.9 - 8.0 microns with a resolution R = delta lambda/lambda = 120, G111 covering 8.4 - 13.7 microns with R = 130, and G227 covering 17.6 - 27.7 microns with R = 110. The spectrum shows a rich array of H I lines including Pf alpha (6 to 5), lines of the series n to 6 (Humphreys), n to 7 and n to 8, and the line H I 11 to 9. The strongest line is a blend of Pf alpha, 11 to 7, Hu delta (11 to 6), and possibly He I at 7.46 microns (peak intensity ~ 11 Jy) and the second strongest is a blend of Hu alpha (7 to 6) and H I 10 to 8 at 12.37 microns (peak intensity ~ 6 Jy). The spectrum (in terms of relative line strengths and shape) looks very similar to that of nova V339 Del (Gehrz, R. D., et al. 2018, ApJ, 812, 132). The complete absence of forbidden metallic emission lines suggests that, even ~ 105 days after commencement of the outburst and ~ 55 days after maximum light, the density of the ejecta remains sufficiently high to quench these lines. The nova remains bright and continued optical and infrared observations are warranted and encouraged. These observations were conducted under SOFIA Cycle 8 Program 08_0006.
