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HD 49798

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HD 49798

A light curve for HD 49798, plotted from TESS data[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Puppis
Right ascension 06h 48m 04.69996s[2]
Declination −44° 18′ 58.4377″[2]
Apparent magnitude (V) 8.287[3]
Characteristics
Spectral type sdO6p
U−B color index −1.259[3]
B−V color index −0.270[3]
Variable type HMXB[4]
Astrometry
Radial velocity (Rv)12.10[5] km/s
Proper motion (μ) RA: −4.73[2] mas/yr
Dec.: 5.39[2] mas/yr
Parallax (π)1.20 ± 0.50 mas[2]
Distance521 ± 14[6] pc
Orbit[6]
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[7]
Mass1.41 ± 0.02[6] M☉
Radius1.08 ± 0.06[6] R☉
Luminosity3,943[8] L☉
Surface gravity (log g)4.25[8] cgs
Temperature47,500[8] K
WD
Mass1.220 ± 0.008[6] M☉
Radius1,604+207
−212[9] km
Temperature225,000[9] K
Rotation13.184246634(7) s[6]
Other designations
HD 49798, CD-44°2920, SAO 218207, HIP 32602, AAVSO 0645-44
Database references
SIMBADdata

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.[10]

HD 49798 was discovered in 1964 to be a rare hydrogen-deficient O class subdwarf, and was the brightest known at the time.[11] This was identified as a binary star, but the companion could not be detected visually or spectroscopically.[12]

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;[13] this rotation is speeding up by 72.0±0.6 ns per year.[6] This is detected from the 13-second X-ray pulse, which results from the stellar wind accreting onto the compact object.[10] 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.[10] This system is considered a likely candidate to explode as a type Ia supernova within a few thousand years.[14][15]

References

[edit]
  1. ^ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 27 December 2024.
  2. ^ 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.
  3. ^ 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.
  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. arXiv:1304.1653. Bibcode:2013A&A...553A..46M. doi:10.1051/0004-6361/201321271. S2CID 56402049.
  5. ^ 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.
  6. ^ a b c d e f g 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.
  7. ^ 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.
  8. ^ a b c 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.
  9. ^ a b 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.
  10. ^ 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.
  11. ^ 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.
  12. ^ 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.
  13. ^ 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.
  14. ^ 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.
  15. ^ 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.
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