Astronomy:HD 49798

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Short description: Binary star system in the constellation Puppis
HD 49798
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A light curve for HD 49798, plotted from TESS data[1]
Observation data
Equinox J2000.0]] (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
Proper motion (μ) RA: −4.162[2] mas/yr
Dec.: +5.926[2] mas/yr
Parallax (π)1.9196 ± 0.0501[2] mas
Distance1,700±46 ly
(521±14 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☉
Radius3,580[6] km
Temperature225,000[9] K
Rotation13.184246634(7) s[6]
Other designations
CD−44°2920, HD 49798, HIP 32602, SAO 218207
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 tens of thousands of years.[14][15]

References

  1. ↑ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 Brown, A. G. A. (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics 649: A1. doi:10.1051/0004-6361/202039657. Bibcode: 2021A&A...649A...1G.  Gaia EDR3 record for this source at VizieR.
  3. ↑ 3.0 3.1 3.2 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. 
  4. ↑ "HD 49798". AAVSO. https://vsx.aavso.org/index.php?view=detail.top&oid=235261. 
  5. ↑ 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. 
  6. ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 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. 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. doi:10.1126/science.1176252. PMID 19729650. Bibcode: 2009Sci...325.1222M. 
  8. ↑ 8.0 8.1 8.2 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. ↑ Mereghetti, S.; Pintore, F.; Rauch, T.; La Palombara, N.; Esposito, P.; Geier, S.; Pelisoli, I.; Rigoselli, M. et al. (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. doi:10.1093/mnras/stab1004. 
  10. ↑ 10.0 10.1 10.2 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. 
  11. ↑ 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. 
  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. doi:10.1093/mnras/150.2.215. Bibcode: 1970MNRAS.150..215T. 
  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. doi:10.1016/j.newar.2012.04.001. Bibcode: 2012NewAR..56..122W. 
  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. doi:10.1088/1674-4527/15/11/004. Bibcode: 2015RAA....15.1813L. 



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