Location of 25 Serpentis (circled) | |
Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
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Constellation | Serpens |
Right ascension | 15h46m 05.63636s[1] |
Declination | −01° 48′ 15.0830″[1] |
Apparent magnitude (V) | 5.37 - 5.40[2] |
Characteristics | |
Spectral type | B8IV/V[3] |
U−B color index | −0.40[4] |
B−V color index | −0.05[4] |
Variable type | SPB[5] |
Astrometry | |
Radial velocity (Rv) | 9.50±0.3[6] km/s |
Proper motion (μ) | RA: −23.15[1] mas/yr Dec.: −30.50[1] mas/yr |
Parallax (π) | 7.25 ± 0.31 mas[1] |
Distance | 450 ± 20 ly (138 ± 6 pc) |
Orbit[7] | |
Period (P) | 38.927±0.004 |
Eccentricity (e) | 0.731±0.006 |
Periastron epoch (T) | 2450132.80±0.06 |
Argument of periastron (ω) (secondary) | 201.8±0.8° |
Semi-amplitude (K1) (primary) | 43.1±0.7 km/s |
Semi-amplitude (K2) (secondary) | 86±1 km/s |
Details[8] | |
Mass | 4.1 M☉ |
Luminosity | 383 L☉ |
Temperature | 13,932 K |
Rotational velocity (v sin i) | 80 km/s |
Other designations | |
A2 Ser,[9] 25 Ser, PT Ser, HD 140873, HIP 77227, HR 5863, SAO 140740, BD−01°3092 | |
Database references | |
SIMBAD | data |
25 Serpentis is a star system in the constellationofSerpens Caput. With an apparent magnitude of 5.37, it is just barely visible to the naked eye. The system is estimated to be some 450 light-years (138 parsecs) based on its parallax.[1]
25 Serpentis is a spectroscopic binary,[11] meaning that the individual components are too close to be resolved, but periodic Doppler shifts in their spectra indicate orbital motion. The system consists of a hot B-type giant and an A-type main-sequence star. The two stars orbit each other every 38.9 days, and have a very eccentric orbit, with an orbital eccentricity of 0.731.[7] The primary is a slowly pulsating B-type star, which causes the system to vary by 0.03 magnitudes;[2] for that reason it has been given the variable star designation PT Serpentis.
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