Year: 2025
Type: article
Abstract: We present a 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 × 10 −11 M ⊙ 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 fluorescence is weak, being significantly detected only in the NuSTAR spectrum, but it 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 that were found to be marginally inconsistent. The H-like Mg line is consistent with instrumental broadening only but shows a 300 km s −1 blueshift. He-like Mg and H-like Si lines have no significant shift in velocity but are broadened by about 1000 km s −1 . This suggests either different physical origins or velocity structure differing with plasma temperature.
Source: The Astrophysical Journal
Institutions: Massachusetts Institute of Technology, East Tennessee State University, Center for Astrophysics Harvard & Smithsonian, University of Sheffield, Embry-Riddle Aeronautical University Prescott Arizona Campus, Embry–Riddle Aeronautical University, University of Iowa, University of Alicante
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
OpenAlex ID: W4415946833