Hot thermal X-ray emission from the Be star HD119682

TL;DR

This study analyzes Chandra X-ray observations of the Be star HD119682, revealing stable thermal emission with brightness variability, no pulsations, and spectral features consistent with a thermal plasma model, classifying it as a gamma Cas analog.

Contribution

First detailed high-resolution X-ray spectral analysis of HD119682 confirming its thermal emission nature and classification as a gamma Cas analog.

Findings

Brightness varies on hour timescales.

Spectral distribution remains stable.

No coherent pulsations detected.

Abstract

We present an analysis of a series of four consecutive Chandra high resolution transmission gratings observations, amounting to a total of 150 ks, of the Be X-ray source HD119682 (= 1WGA J1346.5-6255), a member of the new class of gamma Cas analogs. The Chandra lightcurve shows significant brightness variations on timescales of hours. However, the spectral distribution appears rather stable within each observation and during the whole campaign. A detailed analysis is not able to detect any coherent pulsation up to a frequency of 0.05 Hz. The Chandra HETG spectrum seems to be devoid of any strong emission line, including Fe alpha fluorescence. The continuum is well described with the addition of two collisionally ionized plasmas of temperatures kT = 15 keV and 0.2 keV respectively, by the apec model. Models using photoionized plasma components (mekal) or non thermal components (powerlaw) give poorer fits, giving support to the pure thermal scenario. These two components are absorbed by a single column with N_H=(0.20^+0.15-0.03) x 10^22 cm^-2 compatible with the interstellar value. We conclude that HD119682 can be regarded as a pole-on gamma Cas analog.