HD 2942

HD 2942 is a triple star system[3] in the constellation Andromeda located approximately 170 parsecs (550 ly) away.

HD 2942
Observation data
Epoch J2000      Equinox J2000
Constellation Andromeda
Right ascension 00h 32m 49.0863s[1]
Declination +28° 16′ 48.8676″[1]
Apparent magnitude (V) 6.33[2]
Characteristics
Spectral type K0III+G6V+G8V[3]
U−B color index 0.80[2]
B−V color index 0.99[2]
Astrometry
Radial velocity (Rv)−10.50±0.14[1] km/s
Proper motion (μ) RA: −5.695±0.072[1] mas/yr
Dec.: 6.101±0.039[1] mas/yr
Parallax (π)5.8690 ± 0.0434[1] mas
Distance556 ± 4 ly
(170 ± 1 pc)
Orbit[3]
PrimaryHD 2942Ba
CompanionHD 2942Bb
Period (P)7.4887 days
Eccentricity (e)0.055
Periastron epoch (T)HJD 2,451,060.5586
Argument of periastron (ω)
(secondary)		293.40°
Semi-amplitude (K1)
(primary)		64.01 km/s
Semi-amplitude (K2)
(secondary)		66.34 km/s
Details[3]
HD 2942A
Mass3.17 M☉
HD 2942B
Mass0.89 (Ba) 0.85 (Bb) M☉
Other designations
HIP 2583, HR 134, BD+27° 84, SAO 74090, WDS J00328+2817A
Database references
SIMBADdata
Database references
SIMBADdata

The primary component, a red giant of spectral type K0III, has an apparent magnitude of 6.33, meaning that it is barely visible with the naked eye under good conditions.[2]

The secondary component is much fainter, with an apparent magnitude 11.26, and is located 8.6 arcseconds away. It is a double-lined spectroscopic binary, where two very similar G-type main sequence stars of spectral types G6V and G8V orbit around their common center of mass in 7.489 days. The pair complete an orbit around the primary star every 24,762 years.[3]

Catalogues of stellar multiplicity, like the Washington Double Star Catalog, usually list another component; this star, however, is located much more far away than the other two.[4]

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. Database entry, Catalogue of Stellar Photometry in Johnson's 11-color system (2002 Ed.), J. R. Ducati, CDS ID II/237 Accessed on line 2018-12-05.
  3. Database entry, VizieR Online Data Catalog: Updated Multiple Star Catalog (MSC) (Tokovinin 2018), A. Tokovinin, CDS ID J/ApJS/235/6 Accessed on line 2018-11-29.
  4. "ADS 455 C". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved December 6, 2018.


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