The recurrent nova V3890 Sgr: a near-infrared and optical study of the red giant component and its environment

We present an analysis of the red giant component of the recurrent nova V3890 Sgr, using data obtained before and after its 2019 eruption. Its effective temperature is Teff = 3050 ± 200 K for log g = 0.7, although there are modest changes in Teff. There is an overabundance of both carbon (0.20 ± 0.05 dex) and sodium (1.0 ± 0.3 dex) relative to their solar values, possibly the result of ejecta from the 1990 nova eruption being entrained into the red giant photosphere. We find 12C/13C =25 ± 2, a value similar to that found in red giants in other recurrent novae. The spectrum in the region of the Na I D lines is complex, and includes at least six interstellar components, together with likely evidence for interaction between ejecta from the 2019 eruption and material accumulated in the plane of the binary.

PEPSI (R = 130, 000) observed velocity profiles of various strong emission lines in V3890 Sgr post the 2019 RN eruption at a phase of 0.709. Top: Hα and Hβ. Middle: Permitted lines of He I 5875Å, 6678Å, and the forbidden O III 5006Å line. Bottom: The region of the Na I D lines, for which the velocities are calculated with respect to the D2 line (5889.995Å air). The two narrow features marked by the blue circles are night sky sodium lines. Velocity components of various absorption features are indicated. Note that there are only three distinct Na I D absorption systems: the features at −110.21 km/s and −190.47 km/s are from the same systems as those at +112 km/s and +193 km/s, but for D1.

Read more: Kaminsky et al. 2022, MNRAS, in press