RT Virginis

RT Virginis is a variable star in the equatorial constellation of Virgo, abbreviated RT Vir. It ranges in brightness from an apparent visual magnitude of 7.7 down to 9.7,[3] which is too faint to be visible to the naked eye. Based on parallax measurements made with the VLBI, the distance to this star is approximately 740 light years.[3] It is receding from the Sun with a radial velocity of 17 km/s.[4]

RT Virginis

A visual band light curve for RT Virginis, plotted from ASAS data[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Virgo
Right ascension 13h 02m 37.981s[2]
Declination +05° 11′ 08.36″[2]
Apparent magnitude (V) 7.7 to 9.7[3]
Characteristics
Evolutionary stage AGB[4]
Spectral type M8III[5]
B−V color index 1.352±0.031[6]
Variable type SRb[7]
Astrometry
Radial velocity (Rv)17.3±0.2[4] km/s
Proper motion (μ) RA: +37.037 mas/yr[2]
Dec.: −17.714 mas/yr[2]
Parallax (π)4.417 ± 0.134 mas[3]
Distance740 ± 20 ly
(226 ± 7 pc)
Absolute magnitude (MV)2.94[6]
Details
Mass1.5[8] M☉
Radius390[9] R☉
Luminosity (bolometric)5,012+1,154
−938[4] L☉
Surface gravity (log g)+0.21[10] cgs
Temperature2,902[10] K
Metallicity [Fe/H]−0.33[10] dex
Other designations
RT Vir, BD+05°2708, HD 113285, HIP 63642, SAO 119734, PPM 159423[11]
Database references
SIMBADdata

The long period variability of this star was discovered by W. P. Fleming in 1896, based on photographic plates taken between 1886 and 1895.[12] A. H. Joy in 1942 categorized it as an irregular variable with a stellar classification of M8III.[5] In 1969 it was classified as a semiregular variable star of the SRb type.[13] The period was determined to be 155 days by P. N. Kholopov and associates in 1985, then re-evaluated as 375 days based on AAVSO light curves in 1997. This is an oxygen-rich red giant star on the asymptotic giant branch of its evolution, and is undergoing mass loss due to thermal pulsation.[9]

Water vapor emission in the vicinity of the star was detected in the microwave band by D. F. Dickinson in 1973.[14] This is originating from strong maser emission in a circumstellar gas-dust shell.[15] The flux density of these water masers is over 100 Jy.[9] The star is losing mass at a rate of 3×10−6 M☉·yr−1;[8] the equivalent of the Sun's mass in 3.3 million years. The velocity of the spherically expanding gas is as high as 11 km/s in the water maser region, at a radius of 5 to 25 AU. In a SiO emitting region located ~400 AU from the star, the gas velocity is 7.8 km/s.[16] This outflow appears clumpy and asymmetrical[17] with a strong temporal variation.[15]

References
  1. ASAS All Star Catalogue, The All Sky Automated Survey, retrieved 16 September 2022.
  2. 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. Zhang, Bo; et al. (November 2017), "VLBA Trigonometric Parallax Measurement of the Semi-regular Variable RT Vir", The Astrophysical Journal, 849 (2): 99, Bibcode:2017ApJ...849...99Z, doi:10.3847/1538-4357/aa8ee9, S2CID 125975009, 99.
  4. Brand, J.; et al. (December 2020), "Water vapour masers in long-period variable stars. II. The semi-regular variables R Crt and RT Vir", Astronomy and Astrophysics, 644: A45, arXiv:2011.00294, Bibcode:2020A&A...644A..45B, doi:10.1051/0004-6361/202039157, A45.
  5. Joy, Alfred H. (November 1942), "A Survey of the Spectra and Radial Velocities of the Less Regular M-Type Variable Stars", Astrophysical Journal, 96: 344, Bibcode:1942ApJ....96..344J, doi:10.1086/144469.
  6. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
  7. 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.
  8. Yates, J. A.; et al. (2002), Mineese, Victor; Reid, Mark (eds.), "The H2O maser proper motions of RT Vir and VX Sgr", Cosmic Masers: From Proto-Stars to Black Holes, IAU Symposium, San Francisco: Astronomical Society of the Pacific, 206: 298, Bibcode:2002IAUS..206..298Y.
  9. Imai, H.; et al. (March 1997), "Measurement of shifts in line-of-sight velocities of stellar water masers using VLBI.", Astronomy and Astrophysics, 319: L1–L4, Bibcode:1997A&A...319L...1I.
  10. Sharma, Kaushal; et al. (2016), "New atmospheric parameters and spectral interpolator for the MILES cool stars", Astronomy and Astrophysics, 585: A64, arXiv:1512.04882, Bibcode:2016A&A...585A..64S, doi:10.1051/0004-6361/201526111, S2CID 118576178.
  11. "RT Vir", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2022-09-07
  12. Pickering, E. C.; Fleming, W. P. (April 1896), "Harvard College Observatory, circular no. 6. New variable stars", Astrophysical Journal, 3: 296–302, Bibcode:1896ApJ.....3..296P, doi:10.1086/140219.
  13. 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.
  14. Dickinson, D. F. (March 1976), "Water emission from infrared stars", Astrophysical Journal Supplement Series, 30: 259–271, Bibcode:1976ApJS...30..259D, doi:10.1086/190362.
  15. Mendoza-Torres, J. E.; et al. (December 1997), "Evolution of H2O maser emission in the direction of the semiregular variable RT Virginis during 1985-1996", Astronomy and Astrophysics Supplement Series, 126 (2): 257–266, Bibcode:1997A&AS..126..257M, doi:10.1051/aas:1997263.
  16. Sacuto, S.; et al. (March 2013), "The wind of the M-type AGB star RT Virginis probed by VLTI/MIDI", Astronomy and Astrophysics, 551: A72, arXiv:1301.5872, Bibcode:2013A&A...551A..72S, doi:10.1051/0004-6361/201220524, S2CID 18675130, A72.
  17. Yates, J. A.; et al. (2000), Kastner, J. H.; et al. (eds.), "Is the Outflow from RT Vir Bipolar or Rotating?", Asymmetrical Planetary Nebulae II: From Origins to Microstructures, ASP Conference Series, 199: 79, Bibcode:2000ASPC..199...79Y, ISBN 1-58381-026-9.

Further reading


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