Chandra High Energy Transmission Gratings Spectra of V3890 Sgr

Abstract

The recurrent nova (RN) V3890 Sgr was observed during the seventh day after the onset of its most recent outburst, with the Chandra ACIS-S camera and High Energy Transmission Gratings. A rich emission line spectrum was detected, due to transitions of Fe-L and K-shell ions ranging from neon to iron. The measured absorbed flux is ≈10 −10 erg cm −2 s −1 in the 1.4-15 Årange (0.77-8.86 keV). The line profiles are asymmetric, blueshifted, and skewed toward the blue side, as if the ejecta moving toward us are less absorbed than the receding ejecta. The full width at half-maximum of most emission lines is 1000-1200 km s −1 , with some extended blue wings. The spectrum is thermal and consistent with a plasma in collisional ionization equilibrium with column density 1.3×10 22 cm −2 and at least two components at temperatures of about 1 and 4 keV, possibly a forward and a reverse shock, or regions with differently mixed ejecta and a red giant wind. The spectrum is remarkably similar to the symbiotic RNe V745 Sco and RS Oph, but we cannot distinguish whether the shocks occurred at a distance of a few au from the red giant, or near the giant's photosphere, in a high-density medium containing only a low mass. The ratios of the flux in lines of aluminum, magnesium, and neon relative to the flux in lines of silicon and iron probably indicate a carbon-oxygen white dwarf.

The Super-Soft Source Phase of the recurrent nova V3890 Sgr

“…5). Emission lines arising from ions formed at lower temperatures (such as O vii) can thus be expected to be stronger than in the Chandra observation on day 6.3 (Orio et al 2020). These 'cooler' lines arise longwards of 18 Å where the bright SSS emission is observed.…”

“…The early shock emission before the SSS phase started was observed with Chandra on day 6.3 and has been analysed by Orio et al (2020). In Fig.…”

“…These datasets are described in detail by Page et al (2020) and Singh et al (2021). A deep Chandra observation of the early shock emission was taken on day 6 and is described by Orio et al (2020). We focus here on a deep XMM-Newton observation of V3890 Sgr taken on 2019 September 15 that contains both, shock emission and SSS emission.…”

AT 2019qyl in NGC 300: Internal Collisions in the Early Outflow from a Very Fast Nova in a Symbiotic Binary* †

“…These external interactions also generate non-thermal synchrotron as well as high-energy emission from hot plasma, observed in radio and X-rays for RS Oph for its 1985 and 2006 eruptions (e.g., Hjellming et al 1986;O'Brien et al 2006;Sokoloski et al 2006), and more recently for other embedded novae (e.g., Nelson et al 2012;Delgado & Hernanz 2019;Orio et al 2020). V407 Cyg, in fact, was the first gamma-ray detected nova (e.g., Abdo et al 2010).…”

Galactic and Extragalactic Novae – A Multiwavelenght Review

“…During the recent years, recurrent novae T Pyx, V745 Sco and V3890 Sgr underwent outbursts and were monitored at all wavelengths (see e.g. [73], [52], [113], [109]).…”