Echelle spectroscopy of RS Oph at day +0.87 from optical discovery

ATel #14840; U. Munari (INAF Padova) and P. Valisa (ANS Collaboration)
on 9 Aug 2021; 19:45 UT
Credential Certification: U. Munari (ulisse.munari@oapd.inaf.it)

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Spectroscopic observations of the symbiotic star and recurrent nova RS Oph have been obtained with Varese 0.84m + Echelle and Asiago 1.22 + BC on 2021 July 9.80 UT, about 0.87 days past the discovery of the 2021 outburst on July 8.93 UT by K. Geary (VSNET alert N.26131), and soon detected in gamma-rays by Fermi-LAT (Cheung et al. ATel #14834). Our Echelle spectrum covers the range 4250-8900 Ang at 20,000 resolving power, the BC spectrum extends from 3200 to 7800 Ang, at 2.3 Ang/pix dispersion, and are rather different from the spectrum described in ATel #14836.

The spectrum of RS Oph is characterized by very broad emissions lines with superimposed very narrow components. Overall there is an excellent match with a similar spectrum we obtained on RS Oph less than 1 day into the 2006 eruption.

The broad emission lines resemble He/N novae, with strong Balmer and HeI (4922, 5016, 5876, 6678, 7065) lines. NII (4651, 5176) is present too. The broad component is characterized by a FWHM=2900 km/s and FWZI=6400 km/s and the presence of deep P-Cyg absorption blue-shifted by -3700 and -2700 km/s. The narrow component is best visible in the Balmer, HeI, and FeII #42 lines, and has a FWHM=39 km/s. A narrow and sharp absorption (FWHM=35 km/s) is located 60 km/s to the blue of the narrow emission component, and could originate in the neutral, external part of the red giant wind.