W Serpentis

W Serpentis

A visual band light curve for W Serpentis, adapted from Piirola et al. (2005)[1]
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Serpens
Right ascension 18h 09m 50.64856s[2]
Declination −15° 33′ 00.2634″[2]
Apparent magnitude (V) 8.42-10.2[3]
Characteristics
Spectral type F8/G2Iaep + AV[4][1]
Variable type W Ser[5]
Astrometry
Proper motion (μ) RA: 0.590 mas/yr
Dec.: 3.058 mas/yr
Parallax (π)1.1340 ± 0.0237 mas[2]
Distance2,880 ± 60 ly
(880 ± 20 pc)
Orbit
Period (P)14.16 days[6]
Semi-major axis (a)17.2 R☉[7]
Eccentricity (e)0[6][7]
Inclination (i)72.5[8]°
Details[7]
cool
Mass1.0 M☉
Radius1.00 R☉
Luminosity0.62 L☉
hot
Mass1.5 M☉
Radius1.34 R☉
Luminosity2.82 L☉
Other designations
BD−15°4842, HD 166126, HIP 88994, SAO 161128
Database references
SIMBADdata

W Serpentis is an eclipsing binary star in the constellation Serpens. It is always too faint to be seen with the naked eye,[9] varying between apparent magnitudes 8.42 and 10.2 with a period of just over 14 days.[3] This is mainly due to eclipses; however, variations in its period indicate there are some innate changes in luminosity of one or both component stars as they interact with each other, and it has been difficult to disentangle the light to determine their nature.[10] The period is increasing by 14 seconds a year, indicating that a massive amount of material is being transferred from the larger fainter star to the smaller brighter one.[1]

The system has been found to contain an accretion disk, and was one of the first discovered W Serpentids, which are eclipsing binaries containing exceptionally strong far-ultraviolet spectral lines.[10] These systems have a high rate of mass transfer between one star and the other, and are thought to evolve first into double periodic variables and then classical Algol variables.[11] In the late stages of mass transfer, such systems can develop an optically thick disc and are segregated as a separate class of W Serpentis stars.[5] The classes may also represent different types of system altogether, with the W Serpentis type being younger and more massive.[12]

The spectral types of the component stars are not known; the hotter brighter component appears spectrally similar to an F-type giant. However, the central star appears to be completely obscured by material and may be a B-type main sequence star. The spectrum of the cooler fainter star has not been identified. Examining the polarised light shows that a jet of material is probably coming from the primary star as well.[1] The properties of the two components are highly uncertain. Their orbital separation has been calculated to be 17.2 R☉[7] or 47.3 R☉.[1] The orbit is generally assumed to be circular,[6][7] although the 9th catalogue of spectroscopic binary orbits gives an eccentric orbit from a very old source.[13] The accretion disc has been calculated at 10.4 R☉ across,[7] The sizes of the two stars are disputed: different sources give masses of 5.5 M☉ and 1.6 M☉ or 1.5 M☉ and 1.0 M☉ for the hot and cool components respectively, and radii of 8.5 R☉ and 17.8 R☉ or 1.3 R☉ and 1.0 R☉ for the hot and cool components respectively.[6][7]

  1. ^ a b c d e Piirola, V.; Berdyugin, A.; Mikkola, S.; Coyne, G. V. (2005). "Polarimetric Study of the Massive Interacting Binary W Serpentis: Discovery of High-Latitude Scattering Spot/Jet". The Astrophysical Journal. 632 (1): 576–89. Bibcode:2005ApJ...632..576P. doi:10.1086/432902.
  2. ^ a b c Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  3. ^ a b VSX (4 January 2010). "W Serpentis". AAVSO Website. American Association of Variable Star Observers. Retrieved 7 July 2014.
  4. ^ Houk, N.; Smith-Moore, M. (1988). "Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars. Volume 4, Declinations -26°.0 to -12°.0". Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars. Volume 4. Bibcode:1988mcts.book.....H.
  5. ^ a b Wilson, R. E. (1989). "The Relation of Algols and W Serpentis Stars". Algols. pp. 191–203. doi:10.1007/978-94-009-2413-0_17. ISBN 978-94-010-7587-9.
  6. ^ a b c d Erdem, A.; Öztürk, O. (2014). "Non-conservative mass transfers in Algols". Monthly Notices of the Royal Astronomical Society. 441 (2): 1166. Bibcode:2014MNRAS.441.1166E. doi:10.1093/mnras/stu630.
  7. ^ a b c d e f g Mennickent, R. E.; Otero, S.; Kołaczkowski, Z. (2016). "Interacting binaries W Serpentids and double periodic variables". Monthly Notices of the Royal Astronomical Society. 455 (2): 1728. arXiv:1510.05628. Bibcode:2016MNRAS.455.1728M. doi:10.1093/mnras/stv2433.
  8. ^ Sanad, M. R.; Bobrowsky, M. (2013). "Similarities and differences in the spectral behavior of W Ser and UX Mon in the ultraviolet". Astrophysics and Space Science. 344 (2): 405. Bibcode:2013Ap&SS.344..405S. doi:10.1007/s10509-012-1343-8. S2CID 122761341.
  9. ^ Bortle, John E. (February 2001). "The Bortle Dark-Sky Scale". Sky & Telescope. Sky Publishing Corporation. Archived from the original on 31 March 2014. Retrieved 10 July 2014.
  10. ^ a b Weiland, J. L.; Shore, S. N.; Beaver, E. A.; Lyons, R. W.; Rosenblatt, E. I. (1995). "Goddard High-Resolution Spectrograph Observations of the Interacting Binary System W Serpentis". The Astrophysical Journal. 447: 401. Bibcode:1995ApJ...447..401W. doi:10.1086/175883.
  11. ^ Mennickent, R. E.; Kolaczkowski, Z. (2009). "Interacting Binary Star Environments and the W Ser - DPV - Algol Connection". arXiv:0904.1539 [astro-ph.SR].
  12. ^ Mennickent, R. E.; Kołaczkowski, Z. (2010). "Interacting Binary Stars Environments and the W Ser-DPV-Algol Connection". The Interferometric View on Hot Stars (Eds. Th. Rivinius & M. Curé) Revista Mexicana de Astronomía y Astrofísica, Serie de Conferencias. 38: 23. arXiv:0904.1539. Bibcode:2010RMxAC..38...23M.
  13. ^ 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: 727–732. arXiv:astro-ph/0406573. Bibcode:2004A&A...424..727P. doi:10.1051/0004-6361:20041213. S2CID 119387088.