Chandra/HETG and NuSTAR Observations of V750 Ara, a $γ\,$Cas-type Star
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| Format: | Preprint |
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2025
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| _version_ | 1866912642528968704 |
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| author | 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. |
| author_facet | 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. |
| contents | 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. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2510_10007 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Chandra/HETG and NuSTAR Observations of V750 Ara, a $γ\,$Cas-type Star 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. Solar and Stellar Astrophysics 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. |
| title | Chandra/HETG and NuSTAR Observations of V750 Ara, a $γ\,$Cas-type Star |
| topic | Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2510.10007 |