On the Short-period Eclipsing High-mass X-Ray Binary in NGC 4214
We present the results of our study of the luminous ( L _X ≈ 10 ^39 erg s ^−1 ) X-ray binary CXOU J121538.2+361921 in NGC 4214, the high-mass X-ray binary with the shortest known orbital period. Using Chandra data, we confirm the ≈13,000 s (3.6 hr) eclipse period, and an eclipse duration of ≈2000 s....
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| Format: | Article |
| Language: | English |
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IOP Publishing
2023-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/ace770 |
| _version_ | 1827828264434925568 |
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| author | Zikun Lin Roberto Soria Douglas A. Swartz |
| author_facet | Zikun Lin Roberto Soria Douglas A. Swartz |
| author_sort | Zikun Lin |
| collection | DOAJ |
| description | We present the results of our study of the luminous ( L _X ≈ 10 ^39 erg s ^−1 ) X-ray binary CXOU J121538.2+361921 in NGC 4214, the high-mass X-ray binary with the shortest known orbital period. Using Chandra data, we confirm the ≈13,000 s (3.6 hr) eclipse period, and an eclipse duration of ≈2000 s. From this, we estimate a mass ratio M _2 / M _1 ≳ 3 and a stellar density ρ ≈ 6 g cm ^−3 , which implies that the donor must be a Wolf–Rayet or a stripped helium star. The eclipse egress is consistently much slower than the ingress. This can be explained by denser gas located either in front of the compact object (as expected for a bow shock) or trailing the donor star (as expected for a shadow wind, launched from the shaded side of the donor). There is no change in X-ray spectral shape with changing flux during the egress, which suggests either variable partial covering of the X-ray source by opaque clumps or, more likely, a gray opacity dominated by electron scattering in a highly ionized medium. We identify the optical counterpart from Hubble images. Photometry blueward of ∼5500 Å indicates a bright ( M _B ≈ −3.6 ± 0.3 mag, for a range of plausible extinctions), hot ( T ≈ 90,000 ± 30,000 K) emitter, consistent with the Wolf–Rayet scenario. There is also a bright ( M _I ≈ −5.2 mag), cool ( T ≈ 2700 ± 300 K) component consistent with an irradiated circumbinary disk or with a chance projection of an unrelated asymptotic giant branch star along the same line of sight. |
| first_indexed | 2024-03-12T03:47:33Z |
| format | Article |
| id | doaj.art-74af0b92bd0842988b1dc2e309acfd02 |
| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-12T03:47:33Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-74af0b92bd0842988b1dc2e309acfd022023-09-03T12:38:50ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-0195414610.3847/1538-4357/ace770On the Short-period Eclipsing High-mass X-Ray Binary in NGC 4214Zikun Lin0https://orcid.org/0000-0001-9576-1870Roberto Soria1https://orcid.org/0000-0002-4622-796XDouglas A. Swartz2https://orcid.org/0000-0002-2954-4461Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences , Beijing 100101, People's Republic of China; School of Astronomy and Space Science, University of Chinese Academy of Sciences , Beijing 100049, People's Republic of ChinaSchool of Astronomy and Space Science, University of Chinese Academy of Sciences , Beijing 100049, People's Republic of China; INAF—Osservatorio Astrofisico di Torino , Strada Osservatorio 20, I-10025 Pino Torinese, Italy; Sydney Institute for Astronomy, School of Physics A28, The University of Sydney , Sydney, NSW 2006, AustraliaScience and Technology Institute, Universities Space Research Association , Huntsville, AL 35805, USAWe present the results of our study of the luminous ( L _X ≈ 10 ^39 erg s ^−1 ) X-ray binary CXOU J121538.2+361921 in NGC 4214, the high-mass X-ray binary with the shortest known orbital period. Using Chandra data, we confirm the ≈13,000 s (3.6 hr) eclipse period, and an eclipse duration of ≈2000 s. From this, we estimate a mass ratio M _2 / M _1 ≳ 3 and a stellar density ρ ≈ 6 g cm ^−3 , which implies that the donor must be a Wolf–Rayet or a stripped helium star. The eclipse egress is consistently much slower than the ingress. This can be explained by denser gas located either in front of the compact object (as expected for a bow shock) or trailing the donor star (as expected for a shadow wind, launched from the shaded side of the donor). There is no change in X-ray spectral shape with changing flux during the egress, which suggests either variable partial covering of the X-ray source by opaque clumps or, more likely, a gray opacity dominated by electron scattering in a highly ionized medium. We identify the optical counterpart from Hubble images. Photometry blueward of ∼5500 Å indicates a bright ( M _B ≈ −3.6 ± 0.3 mag, for a range of plausible extinctions), hot ( T ≈ 90,000 ± 30,000 K) emitter, consistent with the Wolf–Rayet scenario. There is also a bright ( M _I ≈ −5.2 mag), cool ( T ≈ 2700 ± 300 K) component consistent with an irradiated circumbinary disk or with a chance projection of an unrelated asymptotic giant branch star along the same line of sight.https://doi.org/10.3847/1538-4357/ace770High mass x-ray binary starsWolf-Rayet starsBlack holes |
| spellingShingle | Zikun Lin Roberto Soria Douglas A. Swartz On the Short-period Eclipsing High-mass X-Ray Binary in NGC 4214 The Astrophysical Journal High mass x-ray binary stars Wolf-Rayet stars Black holes |
| title | On the Short-period Eclipsing High-mass X-Ray Binary in NGC 4214 |
| title_full | On the Short-period Eclipsing High-mass X-Ray Binary in NGC 4214 |
| title_fullStr | On the Short-period Eclipsing High-mass X-Ray Binary in NGC 4214 |
| title_full_unstemmed | On the Short-period Eclipsing High-mass X-Ray Binary in NGC 4214 |
| title_short | On the Short-period Eclipsing High-mass X-Ray Binary in NGC 4214 |
| title_sort | on the short period eclipsing high mass x ray binary in ngc 4214 |
| topic | High mass x-ray binary stars Wolf-Rayet stars Black holes |
| url | https://doi.org/10.3847/1538-4357/ace770 |
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