Betelgeuse's Buddy: X-Ray Constraints on the Nature of $α$ Ori B
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| Main Authors: | , , , , , , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866915523459022848 |
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| author | O'Grady, Anna J. G. O'Connor, Brendan Goldberg, Jared A. Joyce, Meridith Molnár, László Johnson, Christian I. Hare, Jeremy Breivik, Katelyn Drout, Maria R. Moe, Maxwell Calamida, Annalisa |
| author_facet | O'Grady, Anna J. G. O'Connor, Brendan Goldberg, Jared A. Joyce, Meridith Molnár, László Johnson, Christian I. Hare, Jeremy Breivik, Katelyn Drout, Maria R. Moe, Maxwell Calamida, Annalisa |
| contents | The $\sim$$2100$d Long Secondary Period of Betelgeuse's optical lightcurve and radial velocity motivated the prediction of a low-mass stellar companion, expected to be at maximal apparent separation from Betelgeuse around December 2024. We carried out Director's Discretionary Time observations with the Chandra X-ray Observatory to identify any X-ray emission from the companion and constrain its nature as either a compact object or young stellar object (YSO). Past X-ray observations occurred at the wrong phase of the companion's orbit for optimal detection prospects and/or lacked the deep exposure required to constrain the typical X-ray luminosities of YSOs. In our 41.85 ks exposure with Chandra, we do not detect an X-ray source at the position of Betelgeuse. For an estimated hydrogen column density $N_H$$=$$6\times10^{22}$ cm$^{-2}$, we place a limit on the X-ray luminosity of $L_X$$\lesssim$$2\times10^{30}$ erg s$^{-1}$ ($\lesssim$$4.7\times10^{-4}L_\odot$) in $0.5$$-$$8$ keV for a 10 MK plasma temperature spectral model, or $L_X$$\lesssim$$5\times10^{29}$ erg s$^{-1}$ ($\lesssim$$1.2\times10^{-4}L_\odot$) for an absorbed power law with photon index $Γ$$=$$2$. These limits robustly exclude an accreting compact object (white dwarf or neutron star) as the companion. Solar mass YSOs with an age similar to Betelgeuse ($\sim$10 Myr) display a range of X-ray luminosities ($10^{28-32}$ erg s$^{-1}$), and we can place upper bounds within this range for most absorbing columns. Based on these considerations, we conclude that the companion to Betelgeuse is likely a low-mass YSO. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2505_18376 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Betelgeuse's Buddy: X-Ray Constraints on the Nature of $α$ Ori B O'Grady, Anna J. G. O'Connor, Brendan Goldberg, Jared A. Joyce, Meridith Molnár, László Johnson, Christian I. Hare, Jeremy Breivik, Katelyn Drout, Maria R. Moe, Maxwell Calamida, Annalisa Solar and Stellar Astrophysics High Energy Astrophysical Phenomena The $\sim$$2100$d Long Secondary Period of Betelgeuse's optical lightcurve and radial velocity motivated the prediction of a low-mass stellar companion, expected to be at maximal apparent separation from Betelgeuse around December 2024. We carried out Director's Discretionary Time observations with the Chandra X-ray Observatory to identify any X-ray emission from the companion and constrain its nature as either a compact object or young stellar object (YSO). Past X-ray observations occurred at the wrong phase of the companion's orbit for optimal detection prospects and/or lacked the deep exposure required to constrain the typical X-ray luminosities of YSOs. In our 41.85 ks exposure with Chandra, we do not detect an X-ray source at the position of Betelgeuse. For an estimated hydrogen column density $N_H$$=$$6\times10^{22}$ cm$^{-2}$, we place a limit on the X-ray luminosity of $L_X$$\lesssim$$2\times10^{30}$ erg s$^{-1}$ ($\lesssim$$4.7\times10^{-4}L_\odot$) in $0.5$$-$$8$ keV for a 10 MK plasma temperature spectral model, or $L_X$$\lesssim$$5\times10^{29}$ erg s$^{-1}$ ($\lesssim$$1.2\times10^{-4}L_\odot$) for an absorbed power law with photon index $Γ$$=$$2$. These limits robustly exclude an accreting compact object (white dwarf or neutron star) as the companion. Solar mass YSOs with an age similar to Betelgeuse ($\sim$10 Myr) display a range of X-ray luminosities ($10^{28-32}$ erg s$^{-1}$), and we can place upper bounds within this range for most absorbing columns. Based on these considerations, we conclude that the companion to Betelgeuse is likely a low-mass YSO. |
| title | Betelgeuse's Buddy: X-Ray Constraints on the Nature of $α$ Ori B |
| topic | Solar and Stellar Astrophysics High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2505.18376 |