U Lacertae
Binary star in the constellation Lacerta
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U Lacertae is a spectroscopic binary star in the constellation Lacerta.
 | |
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Lacerta |
| Right ascension | 22h 47m 43.42677s[1] |
| Declination | +55° 09′ 30.3036″[1] |
| Apparent magnitude (V) | 9.4 to 12.1[2] |
| Characteristics | |
| Spectral type | M4epIab + B[2] |
| U−B color index | +1.46[3] |
| B−V color index | +2.34[3] |
| Variable type | SRc[2] |
| 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 | |
| U Lac, HIP 112545, PPM 411, GSC 03988-01641, IRC+50446, TYC 3988-1641-1, BD+54°2863, HD 215924, 2MASS J22474341+5509303, AAVSO 2243+54 | |
| 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]
In 1894, T. H. E. C. Espin announced that the star, then called BD +54° 2863, might be a variable star.[13] T. W. Blackhouse confirmed its variability in 1897.[14] It was listed with its variable star designation, U Lacertae, in Annie Jump Cannon's 1907 work Second Catalog of Variable Stars.[15] U Lacertae is classified as a semiregular variable.[2] The periodicity is uncertain but a main period of 150 days and a long secondary period of 550 – 690 days have been suggested.[16] A study of Hipparcos satellite photometry found an amplitude of 0.77 magnitudes and found no periodicity.[17] The General Catalogue of Variable Stars lists an amplitude of 2.7 magnitudes.[2]
Water masers have been detected around U Lacertae, common in the extended atmospheres of very luminous cool stars.[18]