Year: 2025
Type: preprint
Abstract: We present 197 ks HETG and 95 ks NuSTAR spectra of the $γ\,$Cas-type object V750 Ara. The high-resolution X-ray spectra show that the target is similar to other objects of this class. Data are interpreted under the assumption that the X-rays come from an accreting white dwarf, and our analysis implies an accretion rate of about $3\times10^{-11}M_\odot\mathrm{yr}^{-1}$. Emission lines are weak, and predominantly from hydrogen-like ions: Mg XII, Si XIV, and S XVI. H-like and He-like Fe are both present, but Fe K$α$ fluorescence is weak, being significantly detected only in the NuSTAR spectrum, but was not obviously detected in the HETG dispersed or zeroth-order spectra. The flux was variable above a level expected by Poisson statistics. There were no significant changes in the spectral hardness, though we are limited by lack of soft signal below 1 keV. Emission lines of Mg and Si were strong enough to measure velocity offsets and widths which were found to be marginally inconsistent. The H-like Mg line is consistent with instrumental broadening only, but shows a 300 km/s blueshift. He-like Mg and H-like Si lines have no significant shift in velocity but are broadened by about 1000 km/s. This suggests either different physical origins or velocity structure differing with plasma temperature.
Source: arXiv (Cornell University)
Authors: Huenemoerder, David P., Gunderson, Sean J., Ignace, Richard, Nichols, Joy S., Pollock, A. M. T., Pradhan, Pragati, Schulz, Norbert S., Swarm, Dustin K., Torrejón, José M.
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7091186601
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