High resolution X-ray spectroscopy of V3890 Sgr

ATel #13083; Posted by Marina Orio (INAF Padova and U. Wisconsin), Jeremy Drake (CfA), Jan-Uwe Ness (CfA), Ehud Behar (Technion), Paul Kuin (MSSL/UCL), Juan Luna (CONICET/UBA), Kim L. Page (U. Leicester), Sumner Starrfield (ASU), Bob Williams (STScI), E. Aydi, Kirill Sokolovsky (MSU), Matt Darnley (John Moores U.), J. Osborne (U. Leicester), Bob Gehrz and Chick Woodward (U. Minnesota)
on 6 Sep 2019; 15:01 UT
Credential Certification: Marina Orio (orio@astro.wisc.edu)

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V3890 Sgr was observed on 2019-09-03 (day 8 since the onset of the optical outburst; see ATEL #13047, #13050, #13059, #13060, #13062, #13069, #13072, #13081) for 29086 s with the Chandra ACIS-S camera and High Energy Transmission Gratings. A rich emission line spectrum was observed in the 1.2-15 Angstrom range, with several prominent features due to transitions in Fe-L and K-shell ions ranging from neon to iron. Absorbed flux 9.5 x 10^-11 erg/cm²/s was measured with the High Energy Grating (HEG) and 1.06 x 10^-10 erg/cm²/s with the medium Energy Grating (MEG). The line profiles show that the ejecta moving towards us are less absorbed than the receding ejecta, because the red-shifted part of the line appears eroded by differential absorption. The full width at half maximum of most emission lines is 1000-1200 km/s, but some lines have blue wings extending to about 4000 km/s. The spectrum is thermal and is consistent with a plasma in collisional ionization equilibrium with two or multiple regions at different temperature. A very preliminary fit yields equivalent neutral hydrogen column density about 10²² cm^-2 and two plasma components, one at ~0.9 keV (contributing to about 70% of the flux) and a second one at ~4 keV (contributing to about 30% of the flux). The spectrum is very similar to that of another symbiotic recurrent nova, RS Oph, observed with the HETG and with XMM-Newton on the 14th day of the outburst (Nelson et al. 2008, ApJ, 673, 1067; Drake et al. 2009, ApJ, 691, 418; Ness et al. 2009, AJ, 137, 3414) and shares characteristics also with the symbiotic recurrent nova V745 Sco observed with the HETG on the 16th day of the outburst (Drake et al. 2016, ApJ, 825, 95).