SW Virginis

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
Mass1–1.25[8] M☉
Radius244±42[9] R☉
Luminosity4,500±1,100[8] L☉
Surface gravity (log g)−0.3±0.1[8] cgs
Temperature3,060±130[9] K
Metallicity [Fe/H]~0.0[8] dex
Other designations
SW Vir, BD−02° 3653, HD 114961, HIP 64569, SAO 139236, PPM 179000[10]
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.[11] 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.[12][13][9]

The variability of this star was discovered by W. P. Fleming and announced in 1901.[14] 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 the third dredge-up during the thermally pulsating phase of the asymptotic giant branch (AGB).[15]

This is an oxygen-rich non-Mira AGB star[16][17] that is shedding mass at a rate of 4×10−7 M☉·yr−1.[18] An infrared excess indicates the star has a circumstellar dust envelope consisting of grains of matter that have condensed out of expelled gas.[19] This dust shell displays an asymmetric appearance.[16][17] Polarization of light from these dust grains indicate a typical size of less than a μm.[17] 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.[20] 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.[21]

  1. ^ Cite error: The named reference percy_et_al_2001 was invoked but never defined (see the help page).
  2. ^ a b c d e Cite error: The named reference GaiaEDR3 was invoked but never defined (see the help page).
  3. ^ a b c Cite error: The named reference Ducati_2002 was invoked but never defined (see the help page).
  4. ^ a b c Cite error: The named reference Armour_et_al_1990 was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference Keenan_McNeil_1989 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference Samus_et_al_2017 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference Famaey_et_al_2009 was invoked but never defined (see the help page).
  8. ^ a b c d Cite error: The named reference Hadjara was invoked but never defined (see the help page).
  9. ^ a b c Cite error: The named reference Mondal was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Percy_et_al_2008 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Schmidtke_et_al_1986 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference Bogdanov_Cherepashchuk_1990 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference Pickering_et_al_1901 was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference Lebzelter_Hron_2003 was invoked but never defined (see the help page).
  16. ^ a b Cite error: The named reference Guha_Niyogi_et_al_2011 was invoked but never defined (see the help page).
  17. ^ a b c Cite error: The named reference Khouri_et_al_2020 was invoked but never defined (see the help page).
  18. ^ Cite error: The named reference Olofsson_et_al_2002 was invoked but never defined (see the help page).
  19. ^ Cite error: The named reference van_der_Veen_et_al_1995 was invoked but never defined (see the help page).
  20. ^ Cite error: The named reference Zuckerman_Dyck_1986 was invoked but never defined (see the help page).
  21. ^ Cite error: The named reference Ohnaka_et_al_2019 was invoked but never defined (see the help page).