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Binary star in the constellation Lacerta From Wikipedia, the free encyclopedia
U Lacertae is a spectroscopic binary star in the constellation Lacerta.
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Lacerta |
Right ascension | 22h 47m 43.42677s[1] |
Declination | 55° 09′ 30.3036″[1] |
Apparent magnitude (V) | 9.40[2] |
Characteristics | |
Spectral type | M4epIab + B[3] |
U−B color index | +1.46[2] |
B−V color index | +2.34[2] |
Variable type | SRc[3] |
Astrometry | |
Radial velocity (Rv) | −68[4] km/s |
Proper motion (μ) | RA: −3.207 [5] mas/yr Dec.: −3.150 [5] mas/yr |
Parallax (π) | 0.3519 ± 0.0708 mas[5] |
Distance | 2,750[6] pc |
Absolute magnitude (MV) | −5.6[7] |
Details | |
Mass | 22[7] M☉ |
Radius | 1,013[8] R☉ |
Luminosity | 152,000[8] L☉ |
Temperature | 3,535[8] K |
Other designations | |
Database references | |
SIMBAD | data |
Despite being in the constellation of Lacerta, U Lacertae is considered to be a member of the Cepheus OB1 association.[9] It has been listed as a member of the open cluster ASCC 123.[10]
U Lacertae is a binary star consisting of a red supergiant and a small hot companion, similar to VV Cephei. The companion has been identified from a high excitation component in the spectrum and from radial velocity variations, but the orbit is unknown.[11]
U Lacertae is a variable star classified as a semiregular variable.[3] The periodicity is uncertain but a main period of 150 days and a long secondary period of 550 – 690 days have been suggested.[13] A study of Hipparcos satellite photometry found an amplitude of 0.77 magnitudes and found no periodicity.[14] The General Catalogue of Variable Stars lists an amplitude of 2.7 magnitudes.[3]
Water masers have been detected around U Lacertae, common in the extended atmospheres of very luminous cool stars.[15]
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