HW Virginis

HW Virginis, abbreviated HW Vir, is an eclipsing binary system (of the Algol type), approximately 563 light-years away based on the parallax measured by the Gaia spacecraft,[1] 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.[6]

HW Virginis

The HW Virginis system in Celestia.
Observation data
Epoch J2000      Equinox J2000
Constellation Virgo
Right ascension 12h 44m 20.2387s[1]
Declination −08° 40′ 16.8486″[1]
Apparent magnitude (V) 10.69[2]
Characteristics
Spectral type sdB / dM[3]
Variable type eclipsing binary
Astrometry
Proper motion (μ) RA: 8.969±0.175[1] mas/yr
Dec.: −15.677±0.107[1] mas/yr
Parallax (π)5.7972 ± 0.0849 mas[1]
Distance563 ± 8 ly
(172 ± 3 pc)
Absolute magnitude (MV)4.22 (sdB) + 15.59 (dM)[4]
Absolute bolometric
magnitude (Mbol)		1.46 (sdB) + 11.20 (dM)[4]
Orbit[4]
Period (P)0.11671967 d
Semi-major axis (a)0.860 ± 0.010 R☉
Eccentricity (e)<0.0003
Inclination (i)80.98 ± 0.10°
Details[4]
sdB
Mass0.485 ± 0.013 M☉
Radius0.183 ± 0.026 R☉
Luminosity19.7 ± 5.6 L☉
Temperature28488 ± 208 K
dM
Mass0.142 ± 0.004 M☉
Radius0.175 ± 0.026 R☉
Luminosity0.003 ± 0.001 L☉
Temperature3084 ± 889 K
Other designations
BD−07 3477, HIP 62157, 2MASS J12442024-0840168[5]
Database references
SIMBADdata

Eclipse timing variations
A light curve for HW Virginis, plotted from TESS data[7]

Based on variations in the timing of the system's eclipses, in 2008 it was claimed that two giant planets were in orbit around the binary, with masses of 8.47 and 19.2 times the mass of Jupiter orbiting with periods of 9.1 and 15.8 years respectively.[8] The proposed system was later shown to be extremely unstable, with mean lifetimes less than 1000 years in the parameter space allowed by the uncertainties in the data.[9] An alternate, dynamically-stable orbital solution was proposed with a 14.3 Jupiter mass object on a 12-year orbit and an outer companion of 65 Jupiter masses on a 55-year orbit,[10] however it has been noted that the outer companion's orbital parameters are highly unconstrained, again casting doubt on the reality of this model.[9] The problems with modelling this system and the proposed planets orbiting several other post-common envelope binaries has led to the suggestion that the eclipse timing variations used to infer the existence of planets has a non-planetary origin.[11] The eclipse timing variations of HW Virginis were shown to be incompatible with all previous planetary system models as of 2018,[12] and again in 2021.[4] However, eclipse timing variations cannot be explained by known stellar mechanisms either.[4] There is tentative evidence for the presence of a planet from astrometric measurements,[13] with future data releases of the Gaia spacecraft[1] being predicted to be able to fully confirm this.

See also

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27. Bibcode:2000A&A...355L..27H. doi:10.1888/0333750888/2862.
  3. Almeida, L. A.; Jablonski, F.; Tello, J.; Rodrigues, C. V. (2012). "A photometric and spectroscopic study of NSVS 14256825: The second sdOB+dM eclipsing binary". Monthly Notices of the Royal Astronomical Society. 423 (1): 478. arXiv:1203.1266. Bibcode:2012MNRAS.423..478A. doi:10.1111/j.1365-2966.2012.20891.x. S2CID 119177743.
  4. Brown-Sevilla, S. B.; Nascimbeni, V.; Borsato, L.; Tartaglia, L.; Nardiello, D.; Granata, V.; Libralato, M.; Damasso, M.; Piotto, G.; Pollacco, D.; West, R. G.; Colombo, L. S.; Cunial, A.; Piazza, G.; Scaggiante, F. (2021). "A new photometric and dynamical study of the eclipsing binary star HW Virginis". Monthly Notices of the Royal Astronomical Society. 506 (2): 2122–2135. arXiv:2106.15632. doi:10.1093/mnras/stab1843. ISSN 0035-8711.
  5. "HW Virginis". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-09-07.
  6. 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.
  7. "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 December 2021.
  8. 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. S2CID 14152006.
  9. Horner, J.; Hinse, T. C.; Wittenmyer, R. A.; Marshall, J. P.; Tinney, C. G. (2012). "A dynamical analysis of the proposed circumbinary HW Virginis planetary system". Monthly Notices of the Royal Astronomical Society. 427 (4): 2812–2823. arXiv:1209.0608. Bibcode:2012MNRAS.427.2812H. doi:10.1111/j.1365-2966.2012.22046.x. S2CID 53349383.
  10. Beuermann, K.; Dreizler, S.; Hessman, F. V.; Deller, J. (2012). "The quest for companions to post-common envelope binaries. III. A reexamination of HW Virginis". Astronomy & Astrophysics. 543: id.A138. arXiv:1206.3080. Bibcode:2012A&A...543A.138B. doi:10.1051/0004-6361/201219391. S2CID 53680945.
  11. Jonathan Horner; Robert Wittenmyer; Tobias Hinse; Jonathan Marshall; Alex Mustill (2014). "Wobbling Ancient Binaries - Here Be Planets?". arXiv:1401.6742 [astro-ph.EP].
  12. Baran, A. S.; Østensen, R. H.; Telting, J. H.; Vos, J.; Kilkenny, D.; Vučković, M.; Reed, M. D.; Silvotti, R.; Jeffery, C. S.; Parsons, S. G.; Dhillon, V. S.; Marsh, T. R. (2018). "Pulsations and eclipse-time analysis of HW Vir". Monthly Notices of the Royal Astronomical Society. 481 (2): 2721–2735. doi:10.1093/mnras/sty2473.
  13. Baycroft, Thomas A; Triaud, Amaury H M J; Kervella, Pierre (2023-09-13). "New evidence about HW Vir's circumbinary planets from Hipparcos-Gaia astrometry and a reanalysis of the eclipse timing variations using nested sampling". Monthly Notices of the Royal Astronomical Society. 526 (2): 2241–2250. doi:10.1093/mnras/stad2794. ISSN 0035-8711.
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