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τ² Serpentis
Observation data; Epoch J2000.0 Equinox J2000.0 (ICRS)
Constellation	Serpens
Right ascension	15h 32m 09.67495s
Declination	+16° 03′ 22.2056″
Apparent magnitude (V)	6.22
Characteristics
Spectral type	B9V
U−B color index	−0.23
B−V color index	−0.038±0.005
Astrometry
Radial velocity (Rv)	−19.3±2.7 km/s
Proper motion (μ)	RA: −2.92 mas/yr ; Dec.: +6.48 mas/yr
Parallax (π)	6.7936 ± 0.0928 mas
Distance	480 ± 7 ly ; (147 ± 2 pc)
Absolute magnitude (MV)	+0.44
Details
Mass	2.89±0.08 M☉
Radius	2.7 R☉
Luminosity	96.4+15.3; −12.6 L☉
Temperature	10,839+60; −50 K
Rotational velocity (v sin i)	154 km/s
Age	278 Myr
Other designations
	τ2 Ser, 12 Serpentis, BD+16°2797, GC 20880, HD 138527, HIP 76069, HR 5770, SAO 101600, PPM 131484
Database references
SIMBAD	data

Tau² Serpentis, Latinized from τ² Serpentis, is a star in the constellation of Serpens, located approximately 480 light-years from the Sun.^[1] It is a challenge to view with the naked eye, having an apparent visual magnitude of 6.22.^[2] The star is drifting closer with a radial velocity of −19 km/s.^[2]

This object is a late B-type main-sequence star with a stellar classification of B9V.^[3] It is a probable Lambda Boötis star.^[2]^[10] The star is 278^[8] million years old and is spinning with a projected rotational velocity of 154 km/s.^[6] It has nearly three times the mass and radius of the Sun.^[6]^[7] Tau² Serpentis is radiating 96^[6] times the Sun's luminosity from its photosphere at an effective temperature of 10,839 K.^[6]

There is evidence of a possible companion, which is contributing about 15% to the total emission of the system.^[11]

References

^ ^a ^b ^c ^d Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
^ ^a ^b ^c ^d ^e ^f ^g 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.
^ ^a ^b Cowley, A.; et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal, 74: 375–406, Bibcode:1969AJ.....74..375C, doi:10.1086/110819.
^ Hoffleit, D.; Warren, Jr., W. H., The Bright Star Catalogue (5th Revised ed.), CDS. HR 5770. Accessed on line September 19, 2008.
^ ^a ^b van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
^ ^a ^b ^c ^d ^e ^f ^g ^h Zorec, J.; Royer, F. (2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy & Astrophysics, 537: A120, arXiv:1201.2052, Bibcode:2012A&A...537A.120Z, doi:10.1051/0004-6361/201117691, S2CID 55586789.
^ ^a ^b Pasinetti Fracassini, L. E.; et al. (2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)", Astronomy & Astrophysics, 367 (2) (Third ed.): 521–24, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451, S2CID 425754. HD 138527 Accessed on line September 19, 2008.
^ ^a ^b Gontcharov, G. A. (November 2012), "Spatial distribution and kinematics of OB stars", Astronomy Letters, 38 (11): 694–706, arXiv:1606.09028, Bibcode:2012AstL...38..694G, doi:10.1134/S1063773712110035, S2CID 119108982.
^ "tau02 Ser". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-10-18.
^ Murphy, Simon J.; et al. (October 2015), "An Evaluation of the Membership Probability of 212 λ Boo Stars. I. A Catalogue", Publications of the Astronomical Society of Australia, 32: 43, arXiv:1508.03633, Bibcode:2015PASA...32...36M, doi:10.1017/pasa.2015.34, S2CID 59405545, e036
^ Zverko, J.; et al. (January 2013), "Stars with discrepant v sin i as derived from Ca II λ 3933 Å and Mg II λ 4481 Å lines. III. Stars with v sin i ( λ 3933 Å) < v sin i ( λ 4481 Å)", Astrophysical Bulletin, 68 (1): 57–77, Bibcode:2013AstBu..68...57Z, doi:10.1134/S1990341313010069, S2CID 121236297.