HD 49798
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| 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 | |
| Radial velocity (Rv) | 12.10[4] km/s |
| Proper motion (μ) | RA: −4.73[1] mas/yr Dec.: 5.39[1] mas/yr |
| Parallax (π) | 1.20 ± 0.50 mas[1] |
| Distance | 650[3] pc |
| Orbit[3] | |
| Period (P) | 1.55 days |
| Eccentricity (e) | 0.0 |
| Inclination (i) | 82° |
| Details | |
| sdO5.5[5] | |
| Mass | 1.50[3] M☉ |
| Radius | 1.45[6] R☉ |
| Luminosity | 3,943[6] L☉ |
| Surface gravity (log g) | 4.25[6] cgs |
| Temperature | 47,500[6] K |
| WD | |
| Mass | 1.28[3] M☉ |
| Radius | 1,600[7] km |
| Temperature | 225,000[7] K |
| Other designations | |
| 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.[8]
HD 49798 was discovered in 1964 to be a rare hydrogen-deficient O class subdwarf, and was the brightest known at the time.[9] This was identified as a binary star, but the companion could not be detected visually or spectroscopically.[10]
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.[11] This is detected from the 13-second X-ray pulse, which results from the stellar wind accreting onto the compact object.[8] 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.[8] This system is considered a likely candidate to explode as a type Ia supernova within a few thousand years.[12][13]
References[edit]
- ^ a b c d e Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
- ^ a b c Landolt, Arlo U.; Uomoto, Alan K. (2007). "Optical Multicolor Photometry of Spectrophotometric Standard Stars". The Astronomical Journal. 133 (3): 768–790. arXiv:0704.3030. Bibcode:2007AJ....133..768L. doi:10.1086/510485. S2CID 119672730.
- ^ a b c d e 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. arXiv:1304.1653. Bibcode:2013A&A...553A..46M. doi:10.1051/0004-6361/201321271. S2CID 56402049.
- ^ Pourbaix, D.; Tokovinin, A. A.; Batten, A. H.; Fekel, F. C.; Hartkopf, W. I.; Levato, H.; Morrell, N. I.; Torres, G.; Udry, S. (2004). "SB9: The ninth catalogue of spectroscopic binary orbits". Astronomy and Astrophysics. 424 (2): 727–732. arXiv:astro-ph/0406573. Bibcode:2004A&A...424..727P. doi:10.1051/0004-6361:20041213. S2CID 119387088.
- ^ 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. arXiv:1003.0997. Bibcode:2009Sci...325.1222M. doi:10.1126/science.1176252. PMID 19729650. S2CID 206521141.
- ^ a b c d 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.
- ^ a b New X-ray observations of the hot subdwarf binary HD 49798/RX J0648.0–4418, 2021, arXiv:3104.03867
- ^ a b c Chen, Wen-Cong (2022). "X-ray pulsar HD 49798: A contracting white dwarf with a debris disk?". Astronomy & Astrophysics. 662: A79. arXiv:2205.09982. Bibcode:2022A&A...662A..79C. doi:10.1051/0004-6361/202243536. S2CID 248965211.
- ^ Jaschek, Mercedes; Jaschek, Carlos (1963). "HD 49798, a New O-Type Subdwarf". Publications of the Astronomical Society of the Pacific. 75 (445): 365. Bibcode:1963PASP...75..365J. doi:10.1086/127968.
- ^ 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. Bibcode:1970MNRAS.150..215T. doi:10.1093/mnras/150.2.215.
- ^ 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. arXiv:1204.1155. Bibcode:2012NewAR..56..122W. doi:10.1016/j.newar.2012.04.001. S2CID 118740933.
- ^ 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. arXiv:1504.01461. Bibcode:2015RAA....15.1813L. doi:10.1088/1674-4527/15/11/004. S2CID 118683249.
