HD 45364

HD 45364

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Canis Major
Right ascension	06^h 25^m 38.47443^s[1]
Declination	−31° 28′ 51.4285″[1]
Apparent magnitude (V)	8.08[2]
Characteristics
Spectral type	G8V[3]
B−V color index	0.719±0.015[2]
V−R color index	0.01
Astrometry
Radial velocity (Rv)	+16.392±0.0004[1] km/s
Proper motion (μ)	RA: +52.182[1] mas/yr Dec.: −11.926[1] mas/yr
Parallax (π)	29.0797 ± 0.0316 mas[1]
Distance	112.2 ± 0.1 ly (34.39 ± 0.04 pc)
Absolute magnitude (MV)	+5.51[2]
Details[4]
Mass	0.88±0.02 M☉
Radius	0.82±0.01 R☉
Luminosity	0.562±0.004 L☉
Surface gravity (log g)	4.55±0.03 cgs
Temperature	5,540±31 K
Metallicity [Fe/H]	−0.14±0.03[2] dex
Rotational velocity (v sin i)	1.672±0.665[5] km/s
Age	3.4±2.7 Gyr
Other designations
CD−31°3286, HD 30579, HIP 30579, SAO 196806[6]
Database references
SIMBAD	data
Exoplanet Archive	data

HD 45364 is a star in the southern constellation of Canis Major. It is too faint to be visible to the naked eye, having an apparent visual magnitude of 8.08.^[2] The distance to this system is 112 light years based on parallax.^[1] It is drifting further away from the Sun with a radial velocity of +16.4 km/s,^[1] having come within 49 light-years some 1.5 million years ago.^[2]

This object is an ordinary G-type main-sequence star with a stellar classification of G8V,^[3] which indicates it is generating energy through core hydrogen fusion. It is around 3.4 billion years old and is spinning with a projected rotational velocity of 1.7 km/s.^[5] The star has 88% of the mass of the Sun and 82% of the Sun's radius. It is radiating 56% of the luminosity of the Sun from its photosphere at an effective temperature of 5,540 K. As of August 2008 there are two confirmed extrasolar planets (or exoplanets) orbiting around it.^[7]

Planetary system

HD 45364 is one of only a relative few systems that have had more than one exoplanet discovered in its orbit. The two planets, HD 45364 b and HD 45364 c respectively, were both discovered in August 2008 using the radial velocity method. The pair was initially believed to be orbiting the host star with a 3:2 mean motion resonance,^[7] which means the inner planet is completing three orbits for every two orbits of the outer planet.

It was difficult to explain how such resonant configuration of planetary orbits could evolve,^[8] mainly due to too high (4-5 times) orbital eccentrities, although planetary system formation models involving hydrodynamic effects were proposed.^[9]

Hydrodynamic formation scenario of HD45364

As in 2022, refined radial-velocity data shows the planetary orbits are more circular and widely spaced, therefore planets are slightly out of mean motion resonance state.^[10]

The HD 45364 planetary system^[10]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	≥0.1893^+0.0062 −0.006 MJ	0.6793^+0.0016 −0.0015	225.79^+0.81 −0.76	0.067±0.016	—	—
c	≥0.5490^+0.0075 −0.0074 MJ	0.9020±0.0010	345.43^+0.54 −0.57	0.019^+0.011 −0.010	—	—

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. 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. 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. Bonfanti, A.; et al. (2015). "Revising the ages of planet-hosting stars". Astronomy and Astrophysics. 575. A18. arXiv:1411.4302. Bibcode:2015A&A...575A..18B. doi:10.1051/0004-6361/201424951. S2CID 54555839.
5. Soto, M. G.; Jenkins, J. S. (July 2018). "Spectroscopic Parameters and atmosphEric ChemIstriEs of Stars (SPECIES). I. Code description and dwarf stars catalogue". Astronomy & Astrophysics. 615: 28. arXiv:1801.09698. Bibcode:2018A&A...615A..76S. doi:10.1051/0004-6361/201731533. S2CID 119107228. A76.
6. "HD 45364". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-12-19.
7. Correia, A. C. M.; et al. (2009). "The HARPS search for southern extra-solar planets XVI. HD 45364, a pair of planets in a 3:2 mean motion resonance". Astronomy and Astrophysics. 496 (2): 521–526. arXiv:0902.0597. Bibcode:2009A&A...496..521C. doi:10.1051/0004-6361:200810774. S2CID 119235349.
8. Rein, H.; et al. (2010). "The dynamical origin of the multi-planetary system HD 45364" (abstract). Astronomy and Astrophysics. 510 (1): A4. arXiv:0910.5082. Bibcode:2010A&A...510A...4R. doi:10.1051/0004-6361/200913208. S2CID 118459467. (web preprint)
9. Correa-Otto, J. (2013). "A new scenario for the origin of the 3/2 resonant system HD 45364". Astronomy and Astrophysics. 560 (65): A65. arXiv:1307.1822. Bibcode:2013A&A...560A..65C. doi:10.1051/0004-6361/201321917. S2CID 51897058.
10. Li, Zhexing; Kane, Stephen R.; Dalba, Paul A.; Howard, Andrew W.; Isaacson, Howard T. (2022), "New Dynamical State and Habitability of the HD 45364 Planetary System", The Astronomical Journal, 164 (4): 163, arXiv:2209.00120, Bibcode:2022AJ....164..163L, doi:10.3847/1538-3881/ac8d63, S2CID 251979687