Intermediate resolution spectroscopic follow-up observation around H-alpha of the 2021 outburst of the recurrent nova RS Oph

ATel #14909; M. Fajrin, Irfan Imaduddin, Hakim L. Malasan (Institut Teknologi Bandung), Akira Arai (Subaru Telescope, National Astronomical Observatory of Japan), Yoshiharu Shinnaka, Hideyo Kawakita (Koyama Astronomical Observatory, Kyoto Sangyo University)
on 11 Sep 2021; 19:55 UT
Credential Certification: Akira Arai (arai6a@cc.kyoto-su.ac.jp)

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We report a summary of our intermediate-resolution spectra of RS Oph taken firstly on 2021 Aug. 10.5690 UT and consecutively over 16 nights using the LHIRES III spectrograph (1200 grooves/mm grating) equipped with an ST402ME CCD camera. The units are attached to a 10-inch LX-200R Meade telescope (f/10) at Bosscha Observatory of Institut Teknologi Bandung. The standard star HR 7001 was observed to calibrate flux.

As had been predicted in ATel#13810, the first outburst since 2006 of the recurrent nova RS Oph has just occurred. It was discovered and reported to vsnet-alert by Keith Geary ([vsnet-alert 26131]). Also, the Large Area Telescope (LAT) on the Fermi Gamma-ray space telescope discovered it independently (ATel#14834). Follow-up low-resolution spectroscopy using the 3.8 m Seimei telescope was reported by Taguchi et al. (ATel#14838).

Our spectra (Δλ of 260 Å) taken with a resolution λ/Δλ ～ 5000 show broad emission upon which a blue-shifted absorption line (Δ v = -40.272 ± 2.202 km/s on Aug. 10.5690 UT) of H-alpha can be clearly seen. The velocity of the broad Hα emission line is estimated to be around 2800 km/s. The profile and velocity indicate that this outburst is indeed a nova eruption, as is expected. The broad emission line indicates the presence of another shell expanding with high velocity. We measured and determined expansion velocities either from broad emission line and P-Cygni profile, and present herewith the variation in expansion velocities. The expansion velocity smoothly decreased, which is consistent with the 2006 outburst (e.g. Mondal et al. 2018 MNRAS, 474, 4211 and references therein.)

The nova is thought to enter the nebular phase, as can be seen from the low-resolution spectra λ/Δλ ～ 1000 observed from ITERA Astronomical Observatory on 2021 Aug 16.746 UT by I. Hafizah and Aditya A. Yusuf using the Lisa Pack spectrograph equipped with an ATIK 314 L CCD camera. The units are attached to a 10-inch GCR Astrograph telescope (f/8).

Our spectra and measurement results can be seen from the Optional Link URL.

ITB spectra of RS Oph 2021