5 Lacertae
Star in the constellation Lacerta
From Wikipedia, the free encyclopedia
5 Lacertae (5 Lac) is a spectroscopic binary in the constellation Lacerta. Its apparent magnitude is 4.36.
 | |
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Lacerta[1] |
| Right ascension | 22h 29m 31.823s[2] |
| Declination | +47° 42′ 24.79″[2] |
| Apparent magnitude (V) | 4.36[3] |
| Characteristics | |
| Spectral type | K6–M0I + B7/8V[4] |
| U−B color index | +1.11[3] |
| B−V color index | +1.68[3] |
| Variable type | LC[5] |
| Astrometry | |
| Radial velocity (Rv) | −3.4±0.2[6] km/s |
| Proper motion (μ) | RA: −2.554 mas/yr[7] Dec.: −5.372 mas/yr[7] |
| Parallax (π) | 1.4838±0.1383 mas[7] |
| Distance | 2,170+200 −180 ly (665+62 −54 pc)[8] |
| Absolute magnitude (MV) | −4.16[1] |
| Orbit[6] | |
| Period (P) | 41.95±0.20 yr |
| Eccentricity (e) | 0.49±0.01 |
| Periastron epoch (T) | 2427578.3±260 JD |
| Argument of periastron (ω) (secondary) | 323±5.0° |
| Semi-amplitude (K1) (primary) | 12.2±1.2 km/s |
| Semi-amplitude (K2) (secondary) | 112.0±8.2 km/s |
| Details | |
| 5 Lacertae A | |
| Mass | 5.11±0.18[9] M☉ |
| Radius | 427+36 −44[10] R☉ |
| Luminosity | 25,100[11][a] L☉ |
| Temperature | 3,790[11][b] K |
| Rotational velocity (v sin i) | 50[12] km/s |
| Age | 110±10[9] Myr |
| 5 Lacertae B | |
| Rotational velocity (v sin i) | 89[3] km/s |
| Other designations | |
| V412 Lac, BD+46°3719, FK5 3799, HD 213310/1, HIP 111022, HR 8572, SAO 52055[13] | |
| Database references | |
| SIMBAD | data |
Variability
5 Lacertae is a slow irregular variable star with a small amplitude. Photometry from the Hipparcos satellite showed brightness changes between Hipparcos magnitudes 4.39 and 4.56 with no clear periodicity.[5] It was given the variable star designation V412 Lacertae in 1999 in a special name-list dedicated to variables detected from Hipparcos.[15]
Characteristics
The spectrum of 5 Lacertae clearly indicates both a hot component and a cooler component, recognised even in early spectra. Published spectral types for the brighter cool component vary from K4 to M0, with a luminosity class of giant or supergiant. The hotter star is generally classed as a relatively unevolved late B or early A star, but an automated classification program gave it a spectral class of B2V.[16]
Radial velocity variations in the absorption lines from the two separate stars have been measured to determine the orbit. This has an unusually long period of almost 42 years. The two stars have an eccentric orbit with a projected axis of about 15 au.[6]