  | |
| Observation data EpochJ2000[1] EquinoxJ2000[1] | |
|---|---|
| Constellation | Cassiopeia |
| Right ascension | 00h 13m 12.73037s |
| Declination | +62° 02′ 27.1598″ |
| Apparent magnitude (V) | 6.622[2] |
| Characteristics | |
| Spectral type | A2m[3] + GV[4] |
| B−Vcolor index | +0.208[2] |
| J−Hcolor index | +0.035[1] |
| J−Kcolor index | +0.059[1] |
| Astrometry | |
| Radial velocity (Rv) | 8.80 ± 6.28[5] km/s |
| Proper motion (μ) | RA: 72.804[6]mas/yr Dec.: -19.171[6]mas/yr |
| Parallax (π) | 8.0883±0.0269 mas[6] |
| Distance | 403 ± 1 ly (123.6 ± 0.4 pc) |
| Absolute magnitude (MV) | 1.30 (A), 5.62 (B)[4] |
| Orbit[4] | |
| Primary | HD 861 A |
| Companion | HD 861 B |
| Period (P) | 15.9696d |
| Eccentricity (e) | 0.124 |
| Details[4] | |
| HD 861 A | |
| Mass | 2.04 M☉ |
| Radius | 2.775 ± 0.139[7] R☉ |
| Luminosity | 23.8[a] L☉ |
| Surface gravity (log g) | 4.00 cgs |
| Temperature | 8100 K |
| Metallicity [Fe/H] | 0.44 dex |
| Rotational velocity (v sin i) | 37 km/s |
| Age | 724 Myr |
| HD 861 B | |
| Mass | 0.95 M☉ |
| Luminosity | 0.445[a] L☉ |
| Surface gravity (log g) | 4.5 cgs |
| Temperature | 5500 K |
| Other designations | |
| AG+61° 8,BD+61° 16,Gaia DR3 429778586841759104,GC 233,HD 861,HIP 1063,SAO 11044,PPM 12017,TIC 83612641,TYC 4018-687-1,GSC 04018-00687,2MASS J00131272+6202271, Renson 130[1] | |
| Database references | |
| SIMBAD | HD 861 |
HD 861 is aspectroscopic binary star system in the deep northernconstellation ofCassiopeia. With anapparent magnitude of 6.622, the star is faintly visible to the naked eye under very dark skies and readily visible usingbinoculars.[8] It is located approximately 403 light-years (124 parsecs) distant according toGaia EDR3parallax measurements, and is moving further away at a heliocentricradial velocity of 8.80 km/s.
The primary star is a typicalAm star, enriched iniron and especially so inbarium but depleted incarbon,oxygen andcalcium. At an age of 724 million (108.86) years, it is currently amain-sequence starfusinghydrogen intohelium at itscore. It will continue to do so for the next 320 million years until it runs out of core hydrogen at 1.05 billion (109.02) years old, at which point it will leave themain sequence and enter thesubgiant phase.[4]
The secondary star is aG-type main-sequence star slightly less massive than theSun and less than half asluminous.[4]
The orbital properties of the companion were first determined in 1971 by Acker, with anorbital period of 11.2153 days and aneccentricity of 0.22.[9] In 2002, however, Debernardi found an entirely different set of orbital parameters in hisPhDthesis and also discovered thestellar spectra of the secondary star. This new orbit has a longer period of 15.9696 days and a lower eccentricity of 0.124. This was backed up by Budaj et al.,[10] who also independently found the secondary spectra and obtained a mass ratio between the two stars that agreed with Debernardi's research.[4]
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