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SW Virginis

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SW Virginis

A visual band light curve for SW Virginis, adapted from Percy et al. (2001)[1]
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Virgo
Right ascension 13h 14m 04.383s[2]
Declination −02° 48′ 25.13″[2]
Apparent magnitude (V) 6.85[3] (6.65 to 7.95)[4]
Characteristics
Evolutionary stage Asymptotic giant branch
Spectral type M7III:[5]
U−B color index 0.72[3]
B−V color index 1.67[3]
Variable type SRb[6]
Astrometry
Radial velocity (Rv)−15.78±3.51[7] km/s
Proper motion (μ) RA: −35.131 mas/yr[2]
Dec.: −2.769 mas/yr[2]
Parallax (π)5.5526 ± 0.4437 mas[2]
Distance590 ± 50 ly
(180 ± 10 pc)
Details[8]
Radius430 R☉
Luminosity13,000 L☉
Surface gravity (log g)−0.70 cgs
Temperature2,350 K
Other designations
SW Vir, BD−02° 3653, HD 114961, HIP 64569, SAO 139236, PPM 179000[9]
Database references
SIMBADdata

SW Virginis is a star in the equatorial constellation of Virgo, abbreviated SW Vir. It is a variable star that ranges in brightness from an apparent visual magnitude of 6.65 down to 7.95,[4] with a pulsation period of 153.8 days.[10] The star is located at a distance of approximately 590 light years from the Sun based on parallax measurements,[2] but is drifting closer with a radial velocity of −16 km/s.[7] SW Vir is located near the ecliptic and is subject to lunar occultation, which has allowed its angular diameter to be directly measured.[11][12]

The variability of this star was discovered by W. P. Fleming and announced in 1901.[13] It was initially catalogued as an irregular variable but later was classed as a semi-regular variable of type SRb.[4] The stellar classification of M7III: indicates this is an evolved red giant, with the trailing colon indicating some uncertainty about the classification.[5] In 2003, the isotope 99Tc was detected in the atmosphere of SW Vir. The short lifespan of this element is an indicator that the star is undergoing third dredge-up during the thermally pulsating phase of the asymptotic giant branch (AGB).[14]

This is an oxygen-rich non-Mira AGB star[15][16] that is shedding mass at a rate of 4×10−7 M☉·yr−1.[17] An infrared excess indicates the star has a circumstellar dust envelope consisting of grains of matter that have condensed out of expelled gas.[8] This dust shell displays an asymmetric appearance.[15][16] Polarization of light from these dust grains indicate a typical size of less than a μm.[16] The shell's thermal (non-maser) mm-wave spectral line emission from carbon monoxide was detected in 1986, and showed that the circumstellar envelope is expanding at 8.6 km/sec.[18] The spectrum of molecular water has been detected in the star's extended outer atmosphere – out to twice the stellar radius – with a column density of 1019–1020 cm–2.[19]

References

[edit]
  1. ^ Percy, John R.; Wilson, Joseph B.; Henry, Gregory W. (August 2001). "Long-Term VRI Photometry of Small-Amplitude Red Variables. I. Light Curves and Periods". Publications of the Astronomical Society of the Pacific. 113: 983–996. Bibcode:2001PASP..113..983P. doi:10.1086/322153. Retrieved 5 October 2024.
  2. ^ a b c d e 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 c Ducati, J. R. (2002), "Catalogue of Stellar Photometry in Johnson's 11-color system.", VizieR Online Data Catalog, CDS/ADC Collection of Electronic Catalogues, vol. 2237, Bibcode:2002yCat.2237....0D.
  4. ^ a b c Armour, J. E.; et al. (October 1990), "A Period Analysis of the Semi-Regular Variable SW Vir", Information Bulletin on Variable Stars, 3521: 1, Bibcode:1990IBVS.3521....1A.
  5. ^ a b Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245, Bibcode:1989ApJS...71..245K, doi:10.1086/191373.
  6. ^ Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
  7. ^ a b Famaey, B.; et al. (May 2009), "Spectroscopic binaries among Hipparcos M giants. I. Data, orbits, and intrinsic variations", Astronomy and Astrophysics, 498 (2): 627–640, arXiv:0901.0934, Bibcode:2009A&A...498..627F, doi:10.1051/0004-6361/200810698, S2CID 18739721.
  8. ^ a b van der Veen, W. E. C. J.; et al. (March 1995), "The distribution of dust around Asymptotic Giant Branch stars", Astronomy and Astrophysics, 295: 445–458, Bibcode:1995A&A...295..445V.
  9. ^ "SW Vir". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2024-10-03.
  10. ^ Percy, John R.; et al. (May 2008), "Further Studies of the Photometric Variability of Bright Pulsating Red Giants", Publications of the Astronomical Society of the Pacific, 120 (867): 523, Bibcode:2008PASP..120..523P, doi:10.1086/588612.
  11. ^ Schmidtke, P. C.; et al. (April 1986), "Angular diameters by the lunar occultation technique. VII", Astronomical Journal, 91: 961–970, Bibcode:1986AJ.....91..961S, doi:10.1086/114072.
  12. ^ Bogdanov, M. B.; Cherepashchuk, A. M. (August 1990), "Estimation of Brightness Distributions Over Stellar Disks from an Analysis of Infrared Observations of Lunar Occultations - the Red Giants SW-Virginis and FY-Librae", Soviet Astronomy, 34 (4): 393, Bibcode:1990SvA....34..393B.
  13. ^ Pickering, E. C.; et al. (April 1901), "Sixty-four new variable stars", Astrophysical Journal, 13: 226–230, Bibcode:1901ApJ....13..226P, doi:10.1086/140808.
  14. ^ Lebzelter, T.; Hron, J. (December 2003), "Technetium and the third dredge up in AGB stars. I. Field stars", Astronomy and Astrophysics, 411: 533–542, arXiv:astro-ph/0310018, Bibcode:2003A&A...411..533L, doi:10.1051/0004-6361:20031458.
  15. ^ a b Guha Niyogi, Suklima; et al. (October 2011), "Investigating spatial distribution of dust around SW Vir", Astronomical Review, 6 (8): 27–38, Bibcode:2011AstRv...6h..27G.
  16. ^ a b c Khouri, T.; et al. (March 2020), "Inner dusty envelope of the AGB stars W Hydrae, SW Virginis, and R Crateris using SPHERE/ZIMPOL", Astronomy & Astrophysics, 635, id. A200, arXiv:2003.06195, Bibcode:2020A&A...635A.200K, doi:10.1051/0004-6361/201834618.
  17. ^ Olofsson, H.; et al. (September 2002), "Mass loss rates of a sample of irregular and semiregular M-type AGB-variables", Astronomy and Astrophysics, 391: 1053–1067, arXiv:astro-ph/0206172, Bibcode:2002A&A...391.1053O, doi:10.1051/0004-6361:20020841.
  18. ^ Zuckerman, B.; Dyck, H. M. (May 1986). "Carbon Monoxide Emission from Stars in the IRAS and Revised AFGL Catalogs. I. Mass Loss Driven by Radiation Pressure on Dust Grains". Astrophysical Journal. 304: 394–400. Bibcode:1986ApJ...304..394Z. doi:10.1086/164173. Retrieved 5 October 2024.
  19. ^ Ohnaka, K.; et al. (January 2019), "Spatially resolving the atmosphere of the non-Mira-type AGB star SW Vir in near-infrared molecular and atomic lines with VLTI/AMBER", Astronomy & Astrophysics, 621, id. A6, arXiv:1811.05989, Bibcode:2019A&A...621A...6O, doi:10.1051/0004-6361/201834171.
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