HD 49798
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Puppis |
| Right ascension | 06h 48m 04.70015s[2] |
| Declination | −44° 18′ 58.4360″[2] |
| Apparent magnitude (V) | 8.287[3] |
| Characteristics | |
| Spectral type | sdO6p + WD[4] |
| U−B color index | −1.259[3] |
| B−V color index | −0.270[3] |
| Variable type | HMXB[5] |
| Astrometry | |
| Radial velocity (Rv) | +12.10[6] km/s |
| Proper motion (μ) | RA: −4.162[2] mas/yr Dec.: +5.926[2] mas/yr |
| Parallax (π) | 1.9196±0.0501 mas[2] |
| Distance | 1,700±46 ly (521±14 pc)[7] |
| Orbit[7] | |
| Period (P) | 1.547666(6) d |
| Semi-major axis (a) | 2,891,000 ± 15,000 kilometres (0.01933 ± 0.00010 AU) |
| Eccentricity (e) | 0.0 |
| Inclination (i) | 84.5±0.7° |
| Details | |
| sdO5.5[8] | |
| Mass | 1.41±0.02[7] M☉ |
| Radius | 1.08±0.06[7] R☉ |
| Luminosity | 3,943[9] L☉ |
| Surface gravity (log g) | 4.25[9] cgs |
| Temperature | 47,500[9] K |
| WD | |
| Mass | 1.220±0.008[7] M☉ |
| Radius | 3,580[7] km |
| Temperature | 225,000[10] K |
| Rotation | 13.184246634(7) s[7] |
| Other designations | |
| AAVSO 0645-44, CD−44°2920, HD 49798, HIP 32602, SAO 218207 | |
| Database references | |
| SIMBAD | data |
HD 49798 is a binary star in the constellation Puppis about 521 ± 14 parsecs (1,699 ± 46 ly) from Earth. It has an apparent magnitude of 8.3, making it one of the brightest known O class subdwarf stars.[11]
HD 49798 was discovered in 1964 to be a rare hydrogen-deficient O class subdwarf, and was the brightest known at the time.[12] This was identified as a binary star, but the companion could not be detected visually or spectroscopically.[13]
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;[14] this rotation is speeding up by 72.0±0.6 ns per year.[7] This is detected from the 13-second X-ray pulse, which results from the stellar wind accreting onto the compact object.[11] 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.[11] This system is considered a likely candidate to explode as a type Ia supernova within a few tens of thousands of years.[15][16]
References
[edit]- ↑ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 27 December 2024.
- 1 2 3 4 5 Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
- 1 2 3 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.
- ↑ "HD 49798". International Variable Star Index. AAVSO. Retrieved 2026-05-12.
- ↑ 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.
- 1 2 3 4 5 6 7 8 Rigoselli, Michela; De Grandis, Davide; Mereghetti, Sandro; Malacaria, Christian (30 May 2023). "Timing the X-ray pulsating companion of the hot subdwarf HD 49798 with NICER". Monthly Notices of the Royal Astronomical Society. 523 (2): 3043–3048. arXiv:2305.15845. doi:10.1093/mnras/stad1611.
- ↑ 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.
- 1 2 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.
- ↑ Mereghetti, S.; Pintore, F.; Rauch, T.; La Palombara, N.; Esposito, P.; Geier, S.; Pelisoli, I.; Rigoselli, M.; Schaffenroth, V.; Tiengo, A. (2021). "New X-ray observations of the hot subdwarf binary HD 49798/RX J0648.0–4418". Monthly Notices of the Royal Astronomical Society. 504: 920–925. arXiv:2104.03867. doi:10.1093/mnras/stab1004.
- 1 2 3 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.
