Astronomy:HD 49798
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Puppis |
| Right ascension | 06h 48m 04.69996s[1] |
| Declination | −44° 18′ 58.4377″[1] |
| Apparent magnitude (V) | 8.287[2] |
| Characteristics | |
| Spectral type | sdO6p |
| U−B color index | −1.259[2] |
| B−V color index | −0.270[2] |
| Variable type | HMXB[3] |
| Astrometry | |
| Proper motion (μ) | RA: −4.73[1] mas/yr Dec.: 5.39[1] mas/yr |
| Parallax (π) | 1.20 ± 0.50[1] mas |
| Distance | 650[3] pc |
| Orbit[3] | |
| Period (P) | 1.55 days |
| Eccentricity (e) | 0.0 |
| Inclination (i) | 82° |
| Details | |
| sdO5.5[4] | |
| Mass | 1.50[3] M☉ |
| Radius | 1.45[5] R☉ |
| Luminosity | 3,943[5] L☉ |
| Surface gravity (log g) | 4.25[5] cgs |
| Temperature | 47,500[5] K |
| WD | |
| Mass | 1.28[3] M☉ |
| Radius | 1,600[6] km |
| Temperature | 225,000[6] K |
| Other designations | |
HD 49798, CD-44°2920, SAO 218207, HIP 32602, AAVSO 0645-44 | |
| Database references | |
| SIMBAD | data |
HD 49798 is a binary star in the constellation Puppis about 650 parsecs (circa 2119 light-years) from Earth. It has an apparent magnitude of 8.3, making it one of the brightest known O class subdwarf stars.[7]
HD 49798 was discovered in 1964 to be a rare hydrogen-deficient O class subdwarf, and was the brightest known at the time.[8] This was identified as a binary star, but the companion could not be detected visually or spectroscopically.[9]
The X-ray source RX J0648.0-4418 was discovered close to HD 49798's location in the sky. Only the space telescope XMM-Newton was able to identify the source. It is a white dwarf with about 1.3 solar masses, in orbit about HD 49798 and rotating once every 13 seconds.[10] This is detected from the 13-second X-ray pulse, which results from the stellar wind accreting onto the compact object.[7] It has been proposed that the white dwarf is surrounded by a debris disk. In this model, the material of the disk would be funneled onto the poles of the dwarf via the magnetic field, which would explain the observed X-ray pulses.[7] This system is considered a likely candidate to explode as a type Ia supernova within a few thousand years.[11][12]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. doi:10.1051/0004-6361:20078357. Bibcode: 2007A&A...474..653V.
- ↑ 2.0 2.1 2.2 Landolt, Arlo U.; Uomoto, Alan K. (2007). "Optical Multicolor Photometry of Spectrophotometric Standard Stars". The Astronomical Journal 133 (3): 768–790. doi:10.1086/510485. Bibcode: 2007AJ....133..768L.
- ↑ 3.0 3.1 3.2 3.3 3.4 Mereghetti, S.; La Palombara, N.; Tiengo, A.; Sartore, N.; Esposito, P.; Israel, G. L.; Stella, L. (2013). "X-ray emission from the luminous O-type subdwarf HD 49798 and its compact companion". Astronomy & Astrophysics 553: A46. doi:10.1051/0004-6361/201321271. Bibcode: 2013A&A...553A..46M.
- ↑ Mereghetti, S.; Tiengo, A.; Esposito, P.; La Palombara, N.; Israel, G. L.; Stella, L. (2009). "An Ultramassive, Fast-Spinning White Dwarf in a Peculiar Binary System". Science 325 (5945): 1222–1223. doi:10.1126/science.1176252. PMID 19729650. Bibcode: 2009Sci...325.1222M.
- ↑ 5.0 5.1 5.2 5.3 Kudritzki, R. P.; Simon, K. P. (1978). "Non-LTE analysis of subluminous O-star. The hydrogen-deficient subdwarf O-binary HD 49798". Astronomy and Astrophysics 70: 653. Bibcode: 1978A&A....70..653K.
- ↑ 6.0 6.1 New X-ray observations of the hot subdwarf binary HD 49798/RX J0648.0–4418, 2021
- ↑ 7.0 7.1 7.2 Chen, Wen-Cong (2022). "X-ray pulsar HD 49798: A contracting white dwarf with a debris disk?". Astronomy & Astrophysics 662: A79. doi:10.1051/0004-6361/202243536. Bibcode: 2022A&A...662A..79C.
- ↑ Jaschek, Mercedes; Jaschek, Carlos (1963). "HD 49798, a New O-Type Subdwarf". Publications of the Astronomical Society of the Pacific 75 (445): 365. doi:10.1086/127968. Bibcode: 1963PASP...75..365J.
- ↑ Thackeray, A. D. (1970). "The spectroscopic orbit of the O-type subdwarf HD 49798". Monthly Notices of the Royal Astronomical Society 150 (2): 215–225. doi:10.1093/mnras/150.2.215. Bibcode: 1970MNRAS.150..215T.
- ↑ Bisscheroux, B. C.; Pols, O. R.; Kahabka, P.; Belloni, T.; Van Den Heuvel, E. P. J. (1997). "The nature of the bright subdwarf HD 49798 and its X-ray pulsating companion". Astronomy and Astrophysics 317: 815. Bibcode: 1997A&A...317..815B.
- ↑ Wang, Bo; Han, Zhanwen (2012). "Progenitors of type Ia supernovae". New Astronomy Reviews 56 (4): 122. doi:10.1016/j.newar.2012.04.001. Bibcode: 2012NewAR..56..122W.
- ↑ Liu, Dong-Dong; Zhou, Wei-Hong; Wu, Cheng-Yuan; Wang, Bo (2015). "Is the X-ray pulsating companion of HD 49798 a possible type Ia supernova progenitor?". Research in Astronomy and Astrophysics 15 (11): 1813. doi:10.1088/1674-4527/15/11/004. Bibcode: 2015RAA....15.1813L.
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