Tau4 Serpentis
Star in the constellation Serpens / From Wikipedia, the free encyclopedia
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]
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] |
Distance | 710 ± 40 ly (220 ± 10 pc) |
Absolute magnitude (MV) | −0.03[6] |
Details | |
Mass | 3.9[7] M☉ |
Radius | 239[8] R☉ |
Luminosity | 4,969[8] L☉ |
Surface gravity (log g) | −0.14[7] cgs |
Temperature | 3,178[7] K |
Metallicity [Fe/H] | +0.21[7] dex |
Other designations | |
Database references | |
SIMBAD | data |
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.