BD-07 436, also known as WASP-77 since 2012,[7] is a binary star system about 344 light-years away. The star's components appears to have a different age, with the secondary older than 9 billion years, while the primary's age is 5 billion years.[2] The BD-07 436 system's concentration of heavy elements is similar to the Sun. Its stars display moderate chromospheric activity, including x-ray flares.[2]
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cetus |
| Right ascension | 02h 28m 37.226s[1] |
| Declination | −07° 03′ 38.39″[1] |
| Apparent magnitude (V) | 10.12 |
| Characteristics | |
| Evolutionary stage | main-sequence star |
| Spectral type | G8+K5[2] |
| Astrometry | |
| Proper motion (μ) | RA: 88[1] mas/yr Dec.: 8.1[1] mas/yr |
| Parallax (π) | 9.4818 ± 0.1073 mas[3] |
| Distance | 344 ± 4 ly (105 ± 1 pc) |
| Orbit[2][4] | |
| Primary | BD-07 436A |
| Companion | BD-07 436B |
| Semi-major axis (a) | 3.3" (461+200 −140 AU) |
| Eccentricity (e) | 0.51+0.26 −0.22 |
| Inclination (i) | 77+5 −7° |
| Details[5] | |
| BD-07 436A | |
| Mass | 0.903+0.066 −0.059 M☉ |
| Radius | 0.910+0.025 −0.023 R☉ |
| Luminosity | 0.743+0.065 −0.058 L☉ |
| Surface gravity (log g) | 4.476+0.014 −0.015 cgs |
| Temperature | 5617±72 K |
| Metallicity [Fe/H] | −0.10+0.10 −0.11 dex |
| Rotation | 15.4±0.5[6] |
| Rotational velocity (v sin i) | 4.0±0.2 km/s |
| Age | 5[2] Gyr |
| BD-07 436B | |
| Mass | 0.71±0.06[7] M☉ |
| Radius | 0.69±0.12[7] R☉ |
| Surface gravity (log g) | 4.6±0.15[7] cgs |
| Temperature | 5570±240[4] K |
| Metallicity [Fe/H] | -0.11±0.19[7] dex |
| Rotational velocity (v sin i) | 2.8±0.5[7] km/s |
| Age | >9[2] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | 436 data |
The primary is a G-type main-sequence star, BD-07 436A (WASP-77A). The star is rotating rapidly, being spun up by the tides raised by the giant planet WASP-77Ab on its close orbit.[6] The secondary is a K-type main-sequence star BD-07 436B orbiting at a distance of 461+200
−140 AU.[4]
Planetary system
In 2012 a transiting hot Jupiter planet b was detected on a very tight, circular orbit.[7] The planet may have an extended gaseous envelope and is losing mass.[2] Its equilibrium temperature is 1715+26
−25 K,[5]the nightside temperature measured in 2019 is 1786±84 K,[8] and dayside planetary temperature measured in 2020 is 1842+34
−33 K.[9]
Water vapour was detected on the planetary dayside of WASP-77Ab, indicating C/O ratio similar to solar or even lower.[10]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| Ab | 1.667+0.068 −0.064 MJ |
0.02335+0.00045 −0.00043 |
1.36002854±0.00000062 | 0.0074+0.0069 −0.0049 |
88.91+0.74 −0.95° |
1.230+0.031 −0.029 RJ |
References
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