RR Pic (1925): A Chandra X-ray View

TL;DR

This study presents Chandra X-ray observations of RR Pic, revealing its orbital period, spectral features, and plasma properties, including variable hydrogen absorption and emission lines from multiple elements, indicating complex accretion and shock processes.

Contribution

First detailed X-ray spectral analysis of RR Pic revealing orbital modulation, spectral lines, and plasma characteristics of this classical nova remnant.

Findings

Detected orbital period in X-ray wavelengths.

Measured variable hydrogen column density between orbital phases.

Identified emission lines from S, N, O, C, Ne, and Fe.

Abstract

We present the Chandra ACIS-S3 data of the old classical nova RR Pic (1925). The source has a count rate of 0.067+/-0.002 c/s in the 0.3-5.0 keV energy range. We detect the orbital period of the underlying binary system in the X-ray wavelengths. We also find that the neutral Hydrogen column density differs for orbital minimum and orbital maximum spectra with values 0.25(+0.23-0.18)x10^22 cm^-2 and 0.64(+0.13-0.14)x10^22 cm^-2 at 3sigma confidence level. The X-ray spectrum of RR Pic can be represented by a composite model of bremsstrahlung with a photoelectric absorption, two absorption lines centered around 1.1-1.4 keV and 5 Gaussian lines centered at emission lines around 0.3-1.1 keV corresponding to various transitions of S, N, O, C, Ne and Fe . The bremsstrahlung temperature derived from the fits range from 0.99 to 1.60 keV and the unabsorbed X-ray flux is found to be 2.5(+0.4-1.2)x10^-13 erg cm^-2 s^-1 in the 0.3-5.0 keV range with a luminosity of (1.1\pm0.2)x10^31 erg s^-1 at 600 pc. We also detect excess emission in the spectrum possibly originating from the reverse shock in the ejecta.