Galactic center G objects as dust-enshrouded stars near the supermassive black hole
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| Format: | Preprint |
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2024
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| _version_ | 1866913576754610176 |
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| author | Zajaček, Michal Pikhartová, Monika Peissker, Florian |
| author_facet | Zajaček, Michal Pikhartová, Monika Peissker, Florian |
| contents | In this contribution, we revisit the model of a dust-enshrouded star orbiting a low-luminosity galactic nucleus (Zajaček et al. 2014, 2016, 2017). Although it is quite challenging for dust to survive in hot X-ray-emitting plasma surrounding supermassive black holes (SMBHs), we now have an observational evidence that compact dusty objects or ``G'' objects can approach the SMBH in the Galactic center (Sgr A*) on the scale of a few 1000 gravitational radii. Since there are about ten G objects in the Galactic center, it is more likely that they are dust-enshrouded stars whose gaseous-dusty envelopes are stable within the corresponding tidal (Hill) radii of the order of a few astronomical units. Such a length-scale is consistent with their infrared broad-band spectral energy distributions. Broad emission lines, in particular Br$γ$ recombination line, can be interpreted to arise within the accretion stream from the circumstellar envelopes forming a compact disc that is truncated by the stellar magnetic field. Alternatively, they could also be associated with circumstellar accretion-disc outflows as well as the material within a denser bow shock ahead of the star. In comparison with the line origin in the photoionized envelopes that can generally be tidally stretched, the scenario involving the circumstellar accretion-disc inflow or outflow can ensure that the line luminosity is rather stable, except for the viewing-angle effects. We speculate about the origin of dust-enshrouded stars that could be young stellar objects or binary-merger products. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2410_00304 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Galactic center G objects as dust-enshrouded stars near the supermassive black hole Zajaček, Michal Pikhartová, Monika Peissker, Florian Astrophysics of Galaxies High Energy Astrophysical Phenomena In this contribution, we revisit the model of a dust-enshrouded star orbiting a low-luminosity galactic nucleus (Zajaček et al. 2014, 2016, 2017). Although it is quite challenging for dust to survive in hot X-ray-emitting plasma surrounding supermassive black holes (SMBHs), we now have an observational evidence that compact dusty objects or ``G'' objects can approach the SMBH in the Galactic center (Sgr A*) on the scale of a few 1000 gravitational radii. Since there are about ten G objects in the Galactic center, it is more likely that they are dust-enshrouded stars whose gaseous-dusty envelopes are stable within the corresponding tidal (Hill) radii of the order of a few astronomical units. Such a length-scale is consistent with their infrared broad-band spectral energy distributions. Broad emission lines, in particular Br$γ$ recombination line, can be interpreted to arise within the accretion stream from the circumstellar envelopes forming a compact disc that is truncated by the stellar magnetic field. Alternatively, they could also be associated with circumstellar accretion-disc outflows as well as the material within a denser bow shock ahead of the star. In comparison with the line origin in the photoionized envelopes that can generally be tidally stretched, the scenario involving the circumstellar accretion-disc inflow or outflow can ensure that the line luminosity is rather stable, except for the viewing-angle effects. We speculate about the origin of dust-enshrouded stars that could be young stellar objects or binary-merger products. |
| title | Galactic center G objects as dust-enshrouded stars near the supermassive black hole |
| topic | Astrophysics of Galaxies High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2410.00304 |