Early detection of infrared coronal lines in the 2022 eruption of U Sco : a first for this recurrent nova
ATel #15451; D. P.K. Banerjee ( Physical Research Laboratory, India), T. R. Geballe (NOIRLab/Gemini Observatory), A. Evans (U. of. Keele), C. E. Woodward (U. of. Minnesota), R. D. Gehrz (U. of. Minnesota)
on 21 Jun 2022; 20:13 UT
Credential Certification: Dipankar P.K. Banerjee (dpkb12345@gmail.com)
Subjects: Infra-Red, Nova
We report on four epochs of 0.9-2.5um spectra at R =200-1000 of the recurrent nova U Sco,
first observed in outburst by Moriyama (VSNET Alert N0:26798), that were
obtained by the Flamingos 2 spectrograph at the Gemini South Telescope on
2022 June 12.11, 16.13, 17.04, and 19.12 (respectively 5.39, 9.41, 10.32 and
12.40 days after the outburst). Spectra at 2.0-2.3um with R = 1500-3000 were
also obtained for the last two epochs. The spectra show strong and broad HI and
HeI lines throughout superposed on a blue continuum, all weakening with time.
Weaker OI and NI lines are also present. The profile structures are time varying.
Line widths will be reported later, but as a representative example, hydrogen Paschen-beta
1.2818 mic has a FWZI of 10,400 km/s on June 12.11
A major find is the presence of forbidden coronal lines, the first time that such lines
are being reported in any eruption of U Sco. Coronal emission is first seen
on day 9.41, thus beating the record for the earliest detection of an
infrared coronal line in an erupting nova, set by V1674 Her at 11.51d (Woodward et al.
2021, ApJ, 922, 10L). We detect [S IX] 1.25 mic, [Si IX] 1.43 mic, 1.56 mic,
[Si VI] 1.96mic (blended with Brackett delta 1.94 mic), [Al IX] 2.04mic (blended strongly with HeI 2.06mic) and
[Si VII] 2.48mic. Further observations are ongoing. We acknowledge the award of DDT time for this programme GS-2022A-DD-105.
