• Source: SW Virginis

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, with a pulsation period of 153.8 days. The star is located at a distance of approximately 590 light years from the Sun based on parallax measurements, but is drifting closer with a radial velocity of −16 km/s. SW Vir is located near the ecliptic and is subject to lunar occultation, which has allowed its angular diameter to be directly measured.
The variability of this star was discovered by W. P. Fleming and announced in 1901. It was initially catalogued as an irregular variable but later was classed as a semi-regular variable of type SRb. The stellar classification of M7III: indicates this is an evolved red giant, with the trailing colon indicating some uncertainty about the classification. 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).
This is an oxygen-rich non-Mira AGB star that is shedding mass at a rate of 4×10−7 M☉·yr−1. An infrared excess indicates the star has a circumstellar dust envelope consisting of grains of matter that have condensed out of expelled gas. This dust shell displays an asymmetric appearance. Polarization of light from these dust grains indicate a typical size of less than a μm. 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. 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.




References

Kata Kunci Pencarian:

• Santa Maria degli Angeli e dei Martiri
• SW Virginis
• List of largest stars
• R Crateris
• BL Herculis variable
• Lambda Virginis
• Nu Virginis
• Kappa Virginis
• Xi Virginis
• Phi Virginis
• Theta Virginis