LY Aurigae
Binary star in the constellation Auriga
From Wikipedia, the free encyclopedia
LY Aurigae is a multiple star system in the constellation Auriga. It is an eclipsing binary variable star, dropping in brightness by 0.7 magnitudes every 4 days. The system is around 6,800 light years away in the Auriga OB1 stellar association.
LY Aurigae is the bright star, with the red arrow pointing at it, in the southeast corner of this picture of Messier 38 | |
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Auriga |
| Right ascension | 05h 29m 42.650s[1] |
| Declination | +35° 22′ 30.09″[1] |
| Apparent magnitude (V) | 6.85[2] (6.66 - 7.35[3]) |
| Characteristics | |
| Spectral type | O9II + O9III + B0.5III[4] |
| U−B color index | −0.78[5] |
| B−V color index | +0.20[5] |
| Variable type | β Lyr[2] |
| Astrometry | |
| Radial velocity (Rv) | 5.40[6] km/s |
| Proper motion (μ) | RA: −0.20±3.19[1] mas/yr Dec.: −1.17±2.07[1] mas/yr |
| Parallax (π) | 3.28±2.40 mas[1] |
| Distance | 6,800 ly (2,090 pc)[4][a] |
| Absolute magnitude (MV) | −5.62 + −5.11 + −4.43[4] |
| Orbit[4] | |
| Primary | Aa |
| Name | Ab |
| Period (P) | 4.0025 days |
| Semi-major axis (a) | 36.1 R☉ |
| Eccentricity (e) | 0.0 |
| Inclination (i) | 87.7° |
| Semi-amplitude (K1) (primary) | 161.9 km/s |
| Semi-amplitude (K2) (secondary) | 294.3 km/s |
| Orbit[4] | |
| Primary | Ba |
| Name | Bb |
| Period (P) | 20.4642 days |
| Eccentricity (e) | 0.246 |
| Semi-amplitude (K1) (primary) | 33.0 km/s |
| Details[4] | |
| Aa | |
| Mass | 25.5 M☉ |
| Radius | 16.1 R☉ |
| Luminosity | 214,000 L☉ |
| Surface gravity (log g) | 3.425 cgs |
| Temperature | 31,000 K |
| Rotational velocity (v sin i) | 194 km/s |
| Ab | |
| Mass | 14.0 M☉ |
| Radius | 12.6 R☉ |
| Luminosity | 135,000 L☉ |
| Surface gravity (log g) | 3.378 cgs |
| Temperature | 31,150 K |
| Rotational velocity (v sin i) | 152 km/s |
| B | |
| Luminosity | 47,000 L☉ |
| Surface gravity (log g) | 4.00 cgs |
| Temperature | 26,000 K |
| Rotational velocity (v sin i) | 30 km/s |
| Age | 5 Myr |
| Other designations | |
| LY Aurigae, BD+35°1137, HD 35921, SAO 58105, HIP 25733, WDS J05297+3523, AAVSO 0523+35 | |
| Database references | |
| SIMBAD | data |
System
LY Aurigae is a close visual binary. The two stars are magnitude 6.85[7] and magnitude 8.35[8] 0.6 arc-seconds apart. Each star is also a spectroscopic binary.
In 1965, Pavel Mayer reported that the star, then called HD 35921, is a variable star. By 1968, he had determined that it is an eclipsing binary.[10] It was given its variable star designation, LY Aurigae, in 1970.[11] LY Aur A is a double-lined spectroscopic binary with an O9 bright giant and an O9 giant star in contact and eclipsing each other as they orbit every 4 days. It is classified as a Beta Lyr eclipsing variable system. The primary eclipse is 0.69 magnitudes deep and the secondary eclipse is 0.60 magnitudes.[12] Because of the contact nature of the system and the deformed shapes of the stars, the magnitude varies constantly throughout the orbital cycle. The orbital period is slowly changing due to mass exchange between the stars. Each star is over a hundred thousand times the luminosity of the sun.[4]
LY Aur B is a single-lined spectroscopic binary with an orbital period of 20.5 days. It is probably an early B main sequence star and the companion is undetectable. The two stars combined are 47,000 times the luminosity of the sun.[4]
Notes
- Using LY Aurigae's distance modulus of 11.6, its distance from Earth can be calculated by the following equation:
