Tau4 Serpentis

Tau4 Serpentis, Latinized from τ4 Serpentis, is a variable M-type giant star in the constellation of Serpens, approximately 710 light-years from the Earth.[5]

For other stars with this Bayer designation, see Tau Serpentis.
τ4 Serpentis

A visual band light curve for Tau4 Serpentis, plotted from ASAS-SN data[1]
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Serpens
Right ascension 15h 36m 28.1827s[2]
Declination +15° 06′ 05.240″[2]
Apparent magnitude (V) 5.89 to 7.07[3]
Characteristics
Spectral type M5IIIa[4]
B−V color index 1.2[5]
Variable type SRB[3]
Astrometry
Radial velocity (Rv)−26±5[5] km/s
Proper motion (μ) RA: −3.623[2] mas/yr
Dec.: +4.476[2] mas/yr
Parallax (π)4.5628 ± 0.2728 mas[2]
Distance710 ± 40 ly
(220 ± 10 pc)
Absolute magnitude (MV)−0.03[6]
Details
Mass3.9[7] M☉
Radius239[8] R☉
Luminosity4,969[8] L☉
Surface gravity (log g)−0.14[7] cgs
Temperature3,178[7] K
Metallicity [Fe/H]+0.21[7] dex
Other designations
τ4 Ser, 17 Serpentis, BD+15° 2890, GC 20983, HD 139216, HIP 76423, SAO 101641, PPM 131543[5]
Database references
SIMBADdata

With a spectral classification M5IIIa, Tau4 Serpentis is a cool red giant star. The spectrum varies,[4] and some sources classify it between M4IIIe and M6IIIe.[9] Some of its spectral lines show an inverse P Cygni profile,[10] where cold infalling gas on to the star creates redshifted hydrogen absorption lines next to the normal emission lines.[11] It is classified as a semiregular late-type variable, and its magnitude varies between +5.89 and +7.07 with a period of approximately 100 days.[3]

τ4 is unique among the stars with the Bayer designation τ Serpentis as being the only one with no HR catalog number.

References
  1. "ASAS-SN Variable Stars Database". ASAS-SN Variable Stars Database. ASAS-SN. Retrieved 6 January 2022.
  2. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  3. tau 4 Ser, database entry, The combined table of GCVS Vols I-III and NL 67-78 with improved coordinates, General Catalogue of Variable Stars Archived 2017-06-20 at the Wayback Machine, Sternberg Astronomical Institute, Moscow, Russia. Accessed on line September 19, 2008.
  4. 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.
  5. V* tau04 Ser -- Pulsating variable Star, database entry, SIMBAD. Accessed on line September 19, 2008.
  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. Anders, F.; et al. (August 2019). "Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia DR2 stars brighter than G = 18". Astronomy & Astrophysics. 628: A94. arXiv:1904.11302. Bibcode:2019A&A...628A..94A. doi:10.1051/0004-6361/201935765. ISSN 0004-6361.
  8. McDonald, I.; Zijlstra, A. A.; Watson, R. A. (2017). "Fundamental parameters and infrared excesses of Tycho-Gaia stars". Monthly Notices of the Royal Astronomical Society. 471 (1): 770. arXiv:1706.02208. Bibcode:2017MNRAS.471..770M. doi:10.1093/mnras/stx1433. S2CID 73594365.
  9. Skiff, B. A. (2014). "VizieR Online Data Catalog: Catalogue of Stellar Spectral Classifications (Skiff, 2009-2016)". VizieR On-line Data Catalog: B/Mk. Originally Published in: Lowell Observatory (October 2014). 1. Bibcode:2014yCat....1.2023S.
  10. Kolotilov, E. A.; Russev, R. M. (January 1980). "Inverse P Cyg Profile of Halpha in the Spectrum of the Red Giant HD 139216 = tau4 Ser". Information Bulletin on Variable Stars. 1730: 1. Bibcode:1980IBVS.1730....1K.
  11. Galactic Star and Planet Formation Research Group. "Lecture 7: The Collapse of Cores and Infall" (PDF). Department of Physics and Astronomy, University of Toledo. Retrieved 17 July 2015.
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