Beta Caeli

Beta Caeli
Location of β Caeli (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Caelum
Right ascension 04h 42m 03.482s
Declination −37° 08′ 39.59″
Apparent magnitude (V) 5.04
Characteristics
Spectral type F3 V or F3 IV
U−B color index +0.01
B−V color index +0.38
Astrometry
Radial velocity (Rv)27.47±0.24 km/s
Proper motion (μ) RA: +42.561 mas/yr
Dec.: +212.705 mas/yr
Parallax (π)34.6088±0.0531 mas
Distance94.2 ± 0.1 ly
(28.89 ± 0.04 pc)
Absolute magnitude (MV)+2.64
Orbit
PrimaryA
SecondaryB
Period (P)7.5 yr
Semi-major axis (a)4.6 AU
Eccentricity (e)0.6
Inclination (i)27 or 153°
Longitude of the node (Ω)151°
Argument of periastron (ω)
(secondary)		38°
Details
β Cae A
Mass1.482±0.040 M☉
Radius1.902+0.001
−0.004 R☉
Luminosity6.615+0.020
−0.019 L☉
Surface gravity (log g)3.981+0.003
−0.002 cgs
Temperature6,665.7+1.6
−1.4 K
Metallicity = −0.12
Rotation0.8669±0.0013 days
Rotational velocity (v sin i)97.5±4.9 km/s
Age0.2 or 1.17 Gyr
1.941±0.307 Gyr
β Cae B
Mass0.08 or 0.2 M☉
Temperature3,593±160 K
Other designations
β Cae, CD−37°1867, FK5 1130, GJ 176.1, GJ 9165, HD 29992, HIP 21861, HR 1503, SAO 195239
Database references
SIMBADdata

Beta Caeli is a star with an orbiting companion in the southern constellation of Caelum. Its name is a Bayer designation that is Latinized from β Caeli, and abbreviated Beta Cae or β Cae. This star is dimly visible to the naked eye, having an apparent visual magnitude of 5.04. Based upon an annual parallax shift of 34.6 mas as seen from Earth, it is located at a distance of 94 light-years (29 pc). The star is moving away from the Sun with a radial velocity of +27.5 km/s.

Characteristics

Beta Caeli is a probable single-lined spectroscopic binary system, meaning only the spectral lines of the visible component can be seen. This primary component has a stellar classification of F3 V or F3 IV, indicating it is either an F-type main-sequence star or a somewhat more evolved subgiant star, respectively. It has an estimated 1.5 times the mass of the Sun and about 1.9 times the Sun's radius. The star is 200 million to two billion years old and has a high rate of spin with a projected rotational velocity of around 97.5 km/s. It is radiating 6.6 times the luminosity of the Sun from its photosphere at an effective temperature of 6,666 K. Based on the amount of iron detected, the abundance of elements with mass greater than helium is lower than in the Sun.

The low-mass companion is orbiting about 5 AU from the primary, with an orbital period of around seven years. Its exact mass is uncertain; an orbital solution suggest it is close to the brown dwarf regime at around 0.08 M☉, but models of stellar atmospheres suggest a higher mass of 0.2 M☉. It was first detected in 2017 and was believed to be either a brown dwarf or a star with minimum mass around 40 Jupiter masses. In 2022, Beta Caeli was imaged with the Gemini Planet Imager, with a point source that very likely is β Caeli B being detected. This object may be the source of the X-ray emission coming from the same location, which suggests the companion could be a late-type star.

The existence of additional companions beyond 55 astronomical units is ruled out.

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 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.
  2. 1 2 3 4 Cousins, A. W. J. (1973), "UBV photometry of some southern stars", Monthly Notes of the Astronomical Society of Southern Africa, 32: 11, Bibcode:1973MNSSA..32...11C.
  3. 1 2 3 4 Gray, R. O.; et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample", The Astronomical Journal, 132 (1): 161–170, arXiv:astro-ph/0603770, Bibcode:2006AJ....132..161G, doi:10.1086/504637, S2CID 119476992.
  4. 1 2 Torres, C. A. O.; et al. (December 2006), "Search for associations containing young stars (SACY). I. Sample and searching method", Astronomy and Astrophysics, 460 (3): 695–708, arXiv:astro-ph/0609258, Bibcode:2006A&A...460..695T, doi:10.1051/0004-6361:20065602, S2CID 16080025.
  5. 1 2 3 Ammler-von Eiff, Matthias; Reiners, Ansgar (June 2012), "New measurements of rotation and differential rotation in A-F stars: are there two populations of differentially rotating stars?", Astronomy & Astrophysics, 542: A116, arXiv:1204.2459, Bibcode:2012A&A...542A.116A, doi:10.1051/0004-6361/201118724, S2CID 53666672.
  6. 1 2 3 4 5 6 7 8 García, Luciano H.; et al. (August 17, 2022), "High-contrast imaging of HD 29992 and HD 196385 with the Gemini Planet Imager", Monthly Notices of the Royal Astronomical Society, 515 (4): 4999–5008, arXiv:2207.07435, doi:10.1093/mnras/stac1929, ISSN 0035-8711.
  7. ↑ "bet Cae". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-09-09.{{cite web}}: CS1 maint: postscript (link)
  8. 1 2 3 4 Borgniet, Simon; et al. (2017), "Extrasolar planets and brown dwarfs around AF-type stars. IX. The HARPS southern sample", Astronomy & Astrophysics, 599: A57, arXiv:1608.08257, Bibcode:2017A&A...599A..57B, doi:10.1051/0004-6361/201628805, S2CID 118723455.