Interstellar polarization and extinction toward the Recurrent Nova T CrB

TL;DR

This study presents spectropolarimetric observations of the recurrent nova T CrB, estimating interstellar polarization and extinction, and concludes that the observed polarization is due to interstellar dust within 400 pc, with no intrinsic polarization detected.

Contribution

First spectropolarimetric analysis of T CrB during quiescence estimating interstellar polarization and extinction using field stars method.

Findings

Maximum polarization of 0.46% at 5200 Å

Interstellar extinction E_{B-V} ≈ 0.07

Polarization due to dust within 400 pc

Abstract

Spectropolarimetry is a powerful tool for diagnostic of interstellar matter and gives information on the geometry of the ejected material after the novae outbursts. In this paper are presented spectropolarimetric observations of the recurrent nova T CrB at quiescence obtained with FoReRo2 attached to the Cassegrain focus of the 2.0m RCC telescope of the Bulgarian Rozhen National Astronomical Observatory. The interstellar polarization toward T CrB was estimated using the field stars method. The spectropolarimetric observations were obtained from February 2018 to August 2021. In the wavelength range from 4800~\AA~ to 8200~\AA~the maximum of the degree of linear polarization is $P_{max}(obs)(\%) = 0.46 \pm 0.01$ at $\lambda \approx 5200$ \AA. The position angle is $P.A._{obs}=100^{\circ}.8 \pm 0^{\circ}.9$. During the observations, there is no intrinsic polarization in T CrB, and the derived values represent interstellar polarization. The polarization toward T CrB is due to the foreground interstellar dust located at the distance up to $\approx$ 400 pc. Based on the degree of polarization the interstellar extinction toward the T CrB is $E_{B-V} \approx 0.07$.