HD 861 is a spectroscopic binary star system in the deep northern constellation of Cassiopeia. With an apparent magnitude of 6.622, the star is faintly visible to the naked eye under very dark skies and readily visible using binoculars.[8] It is located approximately 403 light-years (124 parsecs) distant according to Gaia EDR3 parallax measurements, and is moving further away at a heliocentric radial velocity of 8.80 km/s.
  | |
| Observation data Epoch J2000[1] Equinox J2000[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−V color index | +0.208[2] |
| J−H color index | +0.035[1] |
| J−K color 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) | 15.9696 d |
| 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 | |
| Database references | |
| SIMBAD | HD 861 |
Stellar properties
editThe primary star is a typical Am star, enriched in iron and especially so in barium but depleted in carbon, oxygen and calcium. At an age of 724 million (108.86) years, it is currently a main-sequence star fusing hydrogen into helium at its core. 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 the main sequence and enter the subgiant phase.[4]
The secondary star is a G-type main-sequence star slightly less massive than the Sun and less than half as luminous.[4]
Orbit
editThe orbital properties of the companion were first determined in 1971 by Acker, with an orbital period of 11.2153 days and an eccentricity of 0.22.[9] In 2002, however, Debernardi found an entirely different set of orbital parameters in his PhD thesis and also discovered the stellar 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]
Notes
edit- ^ a b Calculated from absolute magnitude.
References
edit- ^ a b c d "HD 861". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 5 November 2024.
- ^ a b Høg, E.; et al. (February 2000). "The Tycho-2 Catalogue of the 2.5 Million Brightest Stars". Astronomy and Astrophysics. 355 (1): L27–L30. Bibcode:2000A&A...355L..27H.
- ^ Abt, H.A. (2009). "MK classifications of spectroscopic binaries". VizieR On-line Data Catalog. Centre de Donnees Strasbourg (CDS). Bibcode:2009yCat..21800117A. doi:10.26093/CDS/VIZIER.21800117. Retrieved 5 November 2024.
- ^ a b c d e f g Iliev, I. K.; et al. (1 August 2006). "Abundance analysis of Am binaries and search for tidally driven abundance anomalies - II. HD 861, HD 18778, HD 20320, HD 29479, HD 96528 and HD 108651". Monthly Notices of the Royal Astronomical Society. 370 (2). Oxford University Press (OUP): 819–827. Bibcode:2006MNRAS.370..819I. doi:10.1111/j.1365-2966.2006.10513.x. ISSN 0035-8711.
This article incorporates text from this source, which is available under the CC BY 4.0 license.
- ^ Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
- ^ a b c Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
- ^ Kervella, Pierre; et al. (2019). "Stellar and substellar companions of nearby stars from Gaia DR2". Astronomy & Astrophysics. 623. EDP Sciences: A72. arXiv:1811.08902. doi:10.1051/0004-6361/201834371. ISSN 0004-6361. Record for this source at VizieR.
- ^ Zarenski, Ed (2004). "Limiting Magnitude in Binoculars" (PDF). Cloudy Nights. Archived (PDF) from the original on 21 July 2011. Retrieved 6 May 2011.
- ^ Acker, A. (September 1971). "Orbital elements of the spectroscopic binaries HD 24733 and HD 861". Astronomy & Astrophysics (in French). 14: 189. Bibcode:1971A&A....14..189A.
- ^ Budaj, J.; Iliev, I. Kh.; Fenovcik, M.; Barzova, I.; Richards, M. T.; Geordzheva, E. (12 March 2004). "Discovery of the Secondary in the Spectrum of the SB1 System HD 861". Information Bulletin on Variable Stars. 5509 (1). International Astronomical Union. Bibcode:2004IBVS.5509....1B. ISSN 0374-0676.
