HD 49798

HD 49798 is binary star in the constellation Puppis about 650 parsecs from Earth. It has an apparent magnitude of 8.3.

HD 49798

Observation data Epoch J2000      Equinox J2000
Constellation	Puppis
Right ascension	06^h 48^m 04.69996^s[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[1] mas
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☉
Other designations
HD 49798, CD-44°2920, SAO 218207, HIP 32602, AAVSO 0645-44
Database references
SIMBAD	data

HD 49798 was discovered in 1964 to be a rare hydrogen-deficient O class subdwarf.[7] This was identified as a binary star, but the companion could not be detected visually or spectrscopically.[8]

In its vicinity, scientists discovered an X-ray source with the label RX J0648.0-4418. Only the space telescope XMM-Newton was able to identify the radiation causing object. It is a white dwarf with about 1.3 solar masses, in orbit about HD 49798 and rotating once every 13 seconds.[9] This system is considered a likely candidate to explode as a type Ia supernova within a few thousand years.[10][11]

References

1. Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
2. Landolt, Arlo U.; Uomoto, Alan K. (2007). "Optical Multicolor Photometry of Spectrophotometric Standard Stars". The Astronomical Journal. 133 (3): 768. arXiv:0704.3030. Bibcode:2007AJ....133..768L. doi:10.1086/510485.
3. 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.
4. 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. arXiv:astro-ph/0406573. Bibcode:2004A&A...424..727P. doi:10.1051/0004-6361:20041213.
5. 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. arXiv:1003.0997. Bibcode:2009Sci...325.1222M. doi:10.1126/science.1176252. PMID 19729650.
6. 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.
7. Jaschek, Mercedes; Jaschek, Carlos (1963). "HD 49798, a New O-Type Subdwarf". Publications of the Astronomical Society of the Pacific. 75: 365. Bibcode:1963PASP...75..365J. doi:10.1086/127968.
8. Thackeray, A. D. (1970). "The spectroscopic orbit of the O-type subdwarf HD 49798". Monthly Notices of the Royal Astronomical Society. 150 (2): 215. Bibcode:1970MNRAS.150..215T. doi:10.1093/mnras/150.2.215.
9. 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.
10. 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.
11. 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.