Tau4 Serpentis

τ⁴ Serpentis

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Serpens
Right ascension	15^h 36^m 28.1873^s[1]
Declination	+15° 06′ 05.128″[1]
Apparent magnitude (V)	5.89 to 7.07[2]
Characteristics
Spectral type	M5II-III[1]
B−V color index	1.2[1]
Variable type	SRB[2]
Astrometry
Radial velocity (Rv)	−26 ± 5[1] km/s
Proper motion (μ)	RA: −3.41[1] mas/yr Dec.: 9.55[1] mas/yr
Parallax (π)	6.27 ± 1.00[1] mas
Distance	approx. 520 ly (approx. 160 pc)
Absolute magnitude (MV)	0.5[3]
Other designations
τ^4 Ser, Tau^4 Serpentis, Tau^4 Ser, 17 Serpentis, 17 Ser, τ^4 Serpentis, τ^4 Ser, Tau^4 Serpentis, Tau^4 Ser, BD+15 2890, GC 20983, HD 139216, HIP 76423, PPM 131543, SAO 101641.[1]
Database references
SIMBAD	data

Tau⁴ Serpentis (Tau⁴ Ser, τ⁴ Serpentis, τ⁴ Ser) is a M-type bright giant star in the constellation of Serpens, approximately 520 light-years from the Earth.^[1] It is classified as a semiregular late-type variable star, and its magnitude varies between +5.89 and +7.07 with a period of approximately 100 days.^[2] τ⁴ is unique among the stars with the Bayer designation τ Serpentis as being the only one with no HR catalog number.

References

1. V* tau04 Ser -- Pulsating variable Star, database entry, SIMBAD. Accessed on line September 19, 2008.
2. 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, Sternberg Astronomical Institute, Moscow, Russia. Accessed on line September 19, 2008.
3. From apparent magnitude and parallax.