HD 72945 and HD 72946

HD 72945 & HD 72946

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Cancer
HD 72945
Right ascension	08^h 35^m 50.978^s[1]
Declination	06° 37′ 12.77″[1]
Apparent magnitude (V)	5.91[2]
HD 72946
Right ascension	08^h 35^m 51.267^s[3]
Declination	06° 37′ 21.95″[3]
Apparent magnitude (V)	7.25[2]
Characteristics
HD 72945
Evolutionary stage	Main sequence[4]
Spectral type	F8 V[5]
B−V color index	0.530±0.007[2]
HD 72946
Spectral type	G5V[6]
B−V color index	0.710±0.015[2]
Astrometry
HD 72945
Radial velocity (Rv)	26.61±0.15[7] km/s
Proper motion (μ)	RA: −130.308 mas/yr[1] Dec.: −133.119 mas/yr[1]
Parallax (π)	38.4212 ± 0.1515 mas[1]
Distance	84.9 ± 0.3 ly (26.0 ± 0.1 pc)
Absolute magnitude (MV)	3.91[2]
HD 72946
Radial velocity (Rv)	28.75±0.14[8] km/s
Proper motion (μ)	RA: −136.593 mas/yr[3] Dec.: −137.148 mas/yr[3]
Parallax (π)	38.9809 ± 0.0412 mas[3]
Distance	83.67 ± 0.09 ly (25.65 ± 0.03 pc)
Absolute magnitude (MV)	5.16[2]
Orbit[7]
Primary	HD 72945 A
Period (P)	14.2995±0.0001 d
Semi-major axis (a)	≥4.07 ± 0.05 Gm (5.850 ± 0.072 R☉)
Eccentricity (e)	0.332±0.008
Periastron epoch (T)	2,446,781.30±0.12 JD
Argument of periastron (ω) (secondary)	227.1±3.0°
Semi-amplitude (K1) (primary)	21.95±0.15 km/s
Details
HD 72945
Mass	1.245±0.030[9] M☉
Radius	1.358[10] R☉
Luminosity	2.372[10] L☉
Surface gravity (log g)	4.32[11] cgs
Temperature	6,222[11] K
Metallicity [Fe/H]	0.05[11] dex
Rotational velocity (v sin i)	7.1[11] km/s
Age	1.584±0.952[9] Gyr
HD 72946
Mass	1.02±0.04[12] M☉
Radius	0.97±0.02[12] R☉
Luminosity	0.84[2] L☉
Surface gravity (log g)	4.69[13] cgs
Temperature	5,670[12] K
Metallicity [Fe/H]	0.16[12] dex
Rotational velocity (v sin i)	4.14[9] km/s
Age	1.9^+0.6 −0.5[6] Gyr
Other designations
BD+07 1997, GJ 9271, 310.1, ADS 6886, WDS J08358+0637, STF 1245[14][15]
HD 72945: Boss 2285[16], GC 11781, HIP 42172, HR 3395, SAO 116929, PPM 154707, NLTT 19856[14]
HD 72946: Boss 2286[16], GC 16412, HIP 42173, HR 3396, SAO 116931, PPM 154708, NLTT 19851[15]
Database references
SIMBAD	HD 72945
	HD 72946

HD 72945 and HD 72946 form a co-moving star system in the northern constellation of Cancer.^[17] HD 72945 is a binary star that is dimly visible to the naked eye as a point of light with an apparent visual magnitude of 5.91.^[2] At an angular separation of 10.10″ (as of 2020)^[18] is the fainter companion star HD 72946 at magnitude 7.25.^[2] It is being orbited by a brown dwarf.^[9] The system as a whole is located at a distance of approximately 84 light years from the Sun based on parallax measurements.^[1][3]

The discovery of this double star was announced by F. G. W. Struve in 1782, and later given the discovery code STF 1245.^[18] Their common proper motion was confirmed by A. van Maanen in 1916, and this suggested they are physically associated.^[16] The projected separation of the two systems is 258.9 AU.^[19] Based on astrometric measurements from the Gaia spacecraft, the semimajor axis of this system is 200+52
−41 AU.^[6] Assuming they are gravitationally bound, they would have an orbital period of around 2,500 years.^[20]

There is an additional candidate stellar companion at an angular separation of ~130″, which would make this a four star system. (This object has the 2MASS designation J08354678+0635294.)^[9] Three additional faint companions detected by Struve are most likely background stars.^[7]

HD 72945

The binary nature of HD 72945 was announced in 1919 by A. H. Joy and G. Abetti at the Mount Wilson Observatory. Observed variations in the radial velocity of the primary component inferred an orbiting stellar companion.^[16] This is a single-lined spectroscopic binary system with a period of 14.3 days and an orbital eccentricity of 0.33.^[7] The minimum value for the semimajor axis is only 5.9 times the radius of the Sun, although the actual value is uncertain because the orbital inclination is unknown.^[7]

The visible component of this system has a stellar classification of F8 V,^[5] matching an ordinary F-type main-sequence star. It has 1.25^[9] times the mass of the Sun and 1.4^[10] times the Sun's radius. The star is radiating 2.4^[10] times the luminosity of the Sun from its photosphere at an effective temperature of 6,222 K.^[11] It has an estimated age of approximately 1.6 billion years.^[9] The derived minimum mass for the secondary component is 0.34 M_☉.^[9]

HD 72946

This is a G-type main-sequence star with a class of G5V.^[6] It has about the same size and mass as the Sun.^[12] However, the star is slightly more active than the Sun, and thus probably younger.^[6] It is metal-rich, showing a higher abundance of elements other than hydrogen and helium compared to the Sun.^[21]

In 2016, a candidate brown dwarf companion in orbit around HD 72946 was announced. It was discovered based on radial velocity monitoring over a twenty-year period.^[22] The companion was confirmed in 2020.^[9] It has a classification of L5.0±1.5, a derived temperature of 1,700±90 K, and a mass near the hydrogen-burning limit.^[6] The orbit lies just outside the ice line of the host star, with a semimajor axis of about 6.5 AU.^[9] It is orbiting with a period of 16 years^[6] and an eccentricity of 0.498.^[23]

The HD 72945 and HD 72946 planetary system^[23]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
B	69.5±0.5 MJ	6.492	5,815 ± 37[6]	0.498	1.102°	—

References

1. 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.
2. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
3. 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.
4. Schröder, C.; et al. (January 2009), "Ca II HK emission in rapidly rotating stars. Evidence for an onset of the solar-type dynamo", Astronomy and Astrophysics, 493 (3): 1099–1107, Bibcode:2009A&A...493.1099S, doi:10.1051/0004-6361:200810377.
5. Abt, Helmut A. (December 23, 2008), "Mk Classifications of Spectroscopic Binaries", The Astrophysical Journal Supplement Series, 180 (1): 117–118, Bibcode:2009ApJS..180..117A, doi:10.1088/0067-0049/180/1/117, eISSN 1538-4365, ISSN 0067-0049.
6. Brandt, G. Mirek; et al. (December 2021), "Improved Dynamical Masses for Six Brown Dwarf Companions Using Hipparcos and Gaia EDR3", The Astronomical Journal, 162 (6): 28, arXiv:2109.07525, Bibcode:2021AJ....162..301B, doi:10.3847/1538-3881/ac273e, S2CID 237532125, 301.
7. Duquennoy, A.; Mayor, M. (1991), "Multiplicity among solar-type stars in the solar neighbourhood. II – Distribution of the orbital elements in an unbiased sample", Astronomy & Astrophysics, 248 (2): 485–524, Bibcode:1991A&A...248..485D.
8. 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.
9. Maire, A. -L.; et al. (January 2020), "A dusty benchmark brown dwarf near the ice line of HD 72946", Astronomy & Astrophysics, 633: 10, arXiv:1912.02565, Bibcode:2020A&A...633L...2M, doi:10.1051/0004-6361/201937134, S2CID 208637214, L2.
10. Schofield, Mathew; et al. (2019), "The Asteroseismic Target List for Solar-like Oscillators Observed in 2 minute Cadence with the Transiting Exoplanet Survey Satellite", The Astrophysical Journal Supplement Series, 241 (1): 12, arXiv:1901.10148, Bibcode:2019ApJS..241...12S, doi:10.3847/1538-4365/ab04f5, S2CID 119481586.
11. Luck, R. Earle (January 2017), "Abundances in the Local Region II: F, G, and K Dwarfs and Subgiants", The Astronomical Journal, 153 (1): 19, arXiv:1611.02897, Bibcode:2017AJ....153...21L, doi:10.3847/1538-3881/153/1/21, S2CID 119511744, 21.
12. Hirsch, Lea A.; et al. (2021), "Understanding the Impacts of Stellar Companions on Planet Formation and Evolution: A Survey of Stellar and Planetary Companions within 25 pc", The Astronomical Journal, 161 (3): 134, arXiv:2012.09190, Bibcode:2021AJ....161..134H, doi:10.3847/1538-3881/abd639, S2CID 229297873.
13. Gray, R. O.; et al. (2003), "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 Parsecs: The Northern Sample. I", The Astronomical Journal, 126 (4): 2048, arXiv:astro-ph/0308182, Bibcode:2003AJ....126.2048G, doi:10.1086/378365, S2CID 119417105.
14. "HD 72945", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2022-05-31.
15. "HD 72946", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2022-05-31.
16. Joy, A. H.; Abetti, G. (December 1919), "The orbit of the spectroscopic binary Boss 2285", Astrophysical Journal, 50: 391–393, Bibcode:1919ApJ....50..391J, doi:10.1086/142515.
17. Sinnott, Roger W.; Perryman, Michael A. C. (1997), Millennium Star Atlas, vol. 2, Sky Publishing Corporation and the European Space Agency, p. 761, ISBN 0-933346-83-2.
18. Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122 (6): 3466–71, Bibcode:2001AJ....122.3466M, doi:10.1086/323920.
19. Tokovinin, A.; Kiyaeva, O. (February 2016), "Eccentricity distribution of wide binaries", Monthly Notices of the Royal Astronomical Society, 456 (2): 2070−2079, arXiv:1512.00278, Bibcode:2016MNRAS.456.2070T, doi:10.1093/mnras/stv2825, S2CID 1615080.
20. Tokovinin, Andrei (2014), "From Binaries to Multiples. II. Hierarchical Multiplicity of F and G Dwarfs", The Astronomical Journal, 147 (4): 87, arXiv:1401.6827, Bibcode:2014AJ....147...87T, doi:10.1088/0004-6256/147/4/87, S2CID 56066740.
21. Feltzing, S.; Gustafsson, B. (April 1998), "Abundances in metal-rich stars. Detailed abundance analysis of 47 G and K dwarf stars with [Me/H] > 0.10 dex", Astronomy and Astrophysics Supplement, 129: 237–266, arXiv:astro-ph/9710315, Bibcode:1998A&AS..129..237F, doi:10.1051/aas:1998400, S2CID 14419843.
22. Bouchy, F.; et al. (January 2016), "The SOPHIE search for northern extrasolar planets. VIII. Follow-up of ELODIE candidates: long-period brown-dwarf companions", Astronomy & Astrophysics, 585: 8, arXiv:1511.08397, Bibcode:2016A&A...585A..46B, doi:10.1051/0004-6361/201526347, S2CID 55950304, A46.
23. Balmer, W.O.; et al. (2023). "VLTI/GRAVITY Observations and Characterization of the Brown Dwarf Companion HD 72946 B". The Astrophysical Journal. 956 (2): 24. arXiv:2309.04403. Bibcode:2023ApJ...956...99B. doi:10.3847/1538-4357/acf761. 99.