Epoch J2000.0 Equinox J2000.0 (ICRS)
|Right ascension||12h 44m 20.2367s|
|Declination||−08° 40′ 16.837″|
|Apparent magnitude (V)||10.9|
|Distance||590 ± 65 ly
(181 ± 20 pc)
|Spectral type||sdB / M V|
HW Virginis, abbreviated HW Vir, is an eclipsing binary system (of the Algol type) approximately 590 light-years away (based on the stellar properties and magnitudes: the Hipparcos trigonometric parallax measurement has too high an error value to be useful) in the constellation of Virgo. The system comprises an eclipsing B-type subdwarf star and red dwarf star. The two stars orbit each other every 0.116795 days.
|This section's factual accuracy may be compromised due to out-of-date information. (April 2013)|
In addition, the system has two substellar companions in orbit around the binary: the inner companion HW Virginis c has a mass at least 8.47 times the mass of Jupiter and takes just over 9 years to complete an orbit. The outer companion HW virginis b takes 15.8 years to complete an orbit and has a mass at least 19.2 times Jupiter's mass. According to the definition used by the International Astronomical Union's Working Group on Extrasolar Planets, the inner companion would be classified as a planet, while the outer companion would be classified as a brown dwarf. However the discoverers note that the orbital configuration suggests that the objects formed as planets in a disc, and the formation of planets above the deuterium fusion limit has been predicted by computer models of giant planet formation.
(in order from star)
|c||>8.47 ± 0.42 MJ||3.62 ± 0.52||9.08 ± 0.22||0.31 ± 0.15||—||—|
|b||>19.23 ± 0.24 MJ||5.30 ± 0.23||15.84 ± 0.14||0.46 ± 0.05||—||—|
- Lee, Jae Woo; Kim, Seung-Lee; Kim, Chun-Hwey; Koch, Robert H.; Lee, Chung-Uk; Kim, Ho-Il; Park, Jang-Ho (2009). "The sdB+M Eclipsing System HW Virginis and its Circumbinary Planets". The Astronomical Journal 137 (2): 3181–3190. arXiv:0811.3807. Bibcode:2009AJ....137.3181L. doi:10.1088/0004-6256/137/2/3181.
- Kiss, L. L.; Csák, B.; Szatmáry, K.; Furész, G.; Sziládi, K. (2000). "Spectrophotometry and period analysis of the sdB eclipsing binary HW Virginis". Astronomy and Astrophysics 364: 199–204. arXiv:astro-ph/0010446. Bibcode:2000A&A...364..199K.
- "Definition of a "Planet"". Working Group on Extrasolar Planets (WGESP) of the International Astronomical Union. Retrieved 2009-07-04.
- Mordasini, C. et al. (2007). "Giant Planet Formation by Core Accretion". arXiv:0710.5667v1 [astro-ph].
- Schneider, J. "Notes for star HW Vir". The Extrasolar Planets Encyclopaedia. Retrieved 2008-11-25.
- "Notes for star HW Vir". The Extrasolar Planets Encyclopaedia. Retrieved 25 November 2008.
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