Astronomy:SW Virginis

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Short description: Star in the constellation Virgo
SW Virginis
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A visual band light curve for SW Virginis, adapted from Percy et al. (2001)[1]
Observation data
Equinox J2000.0]] (ICRS)
Constellation Virgo[2]
Right ascension  13h 14m 04.383s[3]
Declination −02° 48′ 25.13″[3]
Apparent magnitude (V) 6.65 to 7.95[4]
Characteristics
Evolutionary stage AGB[5]
Spectral type M7III:[6]
U−B color index 0.72[7]
B−V color index 1.67[7]
Variable type SRb[8]
Astrometry
Radial velocity (Rv)−15.78±3.51[9] km/s
Proper motion (μ) RA: −35.131[3] mas/yr
Dec.: −2.769[3] mas/yr
Parallax (π)5.5526 ± 0.4437[3] mas
Distance590 ± 50 ly
(180 ± 10 pc)
Details
Mass1–1.25[10] M☉
Radius244±42[11] R☉
Luminosity4,500±1,100[10] L☉
Surface gravity (log g)−0.3±0.1[10] cgs
Temperature3,060±130[11] K
Metallicity [Fe/H]~0.0[10] dex
Other designations
SW Vir, BD−02°3653, HD 114961, HIP 64569, SAO 139236, PPM 179000[12]
Database references
SIMBADdata

SW Virginis is a variable star in the equatorial constellation of Virgo, abbreviated SW Vir. It ranges in brightness from an apparent visual magnitude of 6.65 down to 7.95,[4] with a pulsation period of 153.8 days.[13] The star is located at a distance of approximately 590 light years from the Sun based on parallax measurements,[3] but is drifting closer with a radial velocity of −16 km/s.[9] SW Vir is located near the ecliptic and is subject to lunar occultation, which has allowed its angular diameter to be directly measured.[14][15][11]

The variability of this star was discovered by W. P. Fleming and announced in 1901, when it was known as BD−02°3653.[16] It was given its variable star designation, SW Virginis, in 1912.[17] The star 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.[6] 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 the third dredge-up during the thermally pulsating phase of the asymptotic giant branch (AGB).[5]

This is an oxygen-rich non-Mira AGB star[18][19] that is shedding mass at a rate of 4×10−7 M☉·yr−1.[20] An infrared excess indicates the star has a circumstellar dust envelope consisting of grains of matter that have condensed out of expelled gas.[21] This dust shell displays an asymmetric appearance.[18][19] Polarization of light from these dust grains indicate a typical size of less than a μm.[19] 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.[22] 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.[23]

References

  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 (786): 983–996. doi:10.1086/322153. Bibcode: 2001PASP..113..983P. 
  2. ↑ Roman, Nancy G. (1987). "Identification of a constellation from a position". Publications of the Astronomical Society of the Pacific 99 (617): 695. doi:10.1086/132034. Bibcode: 1987PASP...99..695R  Constellation record for this object at VizieR.
  3. ↑ 3.0 3.1 3.2 3.3 3.4 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.
  4. ↑ 4.0 4.1 4.2 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. ↑ 5.0 5.1 Lebzelter, T.; Hron, J. (December 2003), "Technetium and the third dredge up in AGB stars. I. Field stars", Astronomy and Astrophysics 411 (3): 533–542, doi:10.1051/0004-6361:20031458, Bibcode: 2003A&A...411..533L. 
  6. ↑ 6.0 6.1 Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series 71: 245, doi:10.1086/191373, Bibcode: 1989ApJS...71..245K. 
  7. ↑ 7.0 7.1 Ducati, J. R. (2002), "Catalogue of Stellar Photometry in Johnson's 11-color system.", VizieR Online Data Catalog, CDS/ADC Collection of Electronic Catalogues 2237, Bibcode: 2002yCat.2237....0D. 
  8. ↑ Samus, N. N. et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1 61 (1): 80–88, doi:10.1134/S1063772917010085, Bibcode: 2017ARep...61...80S. 
  9. ↑ 9.0 9.1 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, doi:10.1051/0004-6361/200810698, Bibcode: 2009A&A...498..627F. 
  10. ↑ 10.0 10.1 10.2 10.3 Hadjara, M.; Cruzalèbes, P.; Nitschelm, C.; Chen, X.; Michael, E. A.; Moreno, E. (2019-10-01). "A CO-multilayer outer atmosphere for eight evolved stars revealed with VLTI/AMBER". Monthly Notices of the Royal Astronomical Society 489 (2): 2595–2614. doi:10.1093/mnras/stz2240. ISSN 0035-8711. Bibcode: 2019MNRAS.489.2595H. 
  11. ↑ 11.0 11.1 11.2 Mondal, Soumen; Chandrasekhar, T. (2005-08-01). "Angular Diameter Measurements of Evolved Variables by Lunar Occultations at 2.2 and 3.8 Microns". The Astronomical Journal 130 (2): 842–852. doi:10.1086/430457. ISSN 0004-6256. Bibcode: 2005AJ....130..842M. 
  12. ↑ "SW Vir". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=SW+Vir. 
  13. ↑ 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, doi:10.1086/588612, Bibcode: 2008PASP..120..523P. 
  14. ↑ Schmidtke, P. C. et al. (April 1986), "Angular diameters by the lunar occultation technique. VII", Astronomical Journal 91: 961–970, doi:10.1086/114072, Bibcode: 1986AJ.....91..961S. 
  15. ↑ 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. 
  16. ↑ Pickering, E. C. et al. (April 1901), "Sixty-four new variable stars", Astrophysical Journal 13: 226–230, doi:10.1086/140808, Bibcode: 1901ApJ....13..226P. 
  17. ↑ Dunér, Nils Christofer; Hartwig, Ernst; Müller, G. (June 1912). "Benennung von neu entdeckten veränderlichen Sternen". Astronomische Nachrichten 191 (19): 341–358. doi:10.1002/asna.19121911902. Bibcode: 1912AN....191..341.. 
  18. ↑ 18.0 18.1 Guha Niyogi, Suklima et al. (October 2011), "Investigating spatial distribution of dust around SW Vir", Astronomical Review 6 (8): 27–38, doi:10.1080/21672857.2011.11519689, Bibcode: 2011AstRv...6h..27G. 
  19. ↑ 19.0 19.1 19.2 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, doi:10.1051/0004-6361/201834618, Bibcode: 2020A&A...635A.200K. 
  20. ↑ Olofsson, H. et al. (September 2002), "Mass loss rates of a sample of irregular and semiregular M-type AGB-variables", Astronomy and Astrophysics 391 (3): 1053–1067, doi:10.1051/0004-6361:20020841, Bibcode: 2002A&A...391.1053O. 
  21. ↑ 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. 
  22. ↑ 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. doi:10.1086/164173. Bibcode: 1986ApJ...304..394Z. 
  23. ↑ 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, doi:10.1051/0004-6361/201834171, Bibcode: 2019A&A...621A...6O. 



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