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  • 21 Aug, 2019

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HD 34445
HD 34445 is a star in the equatorial constellation of Orion. With an apparent visual magnitude of 7.31, it is a 7th magnitude star that is too dim to be readily visible to the naked eye. The system is located at a distance of 150.5 light years from the Sun based on parallax measurements, but is drifting closer with a high radial velocity of −79 km/s. It is expected to draw as close as 57.5 light-years in ~492,000 years.

This is an ordinary G-type main-sequence star with a stellar classification of G0 V, which means it is a Sun-like star that is generating energy through core hydrogen fusion. It is considered a metal-rich star, showing a much higher metallicity compared to the Sun. Despite this it is an older star and chromospherically quiet, lying about 0.8 magnitudes above the main sequence. This star is larger, hotter, brighter, and more massive than the Sun. It is spinning with a projected rotational velocity of ~3 km/s, giving it a rotation period of around 22 days.

Planetary companions

In 2004, a gas giant was found in orbit around the star, but it was not until 2009 that this planet was confirmed. In 2017, five more planets were found. All have minimum masses significantly greater than that of the Earth, between 16.8 ME and 200.0 ME. The system as configured appears to be dynamically stable.

A 2021 study was only able to confirm HD 34445 b as a planet. HD 34445 e was found to likely be an artifact of the stellar rotation, as its orbital period closely matched to the rotation period of the star, HD 34445 c & d were also found to likely be false positives having orbital periods of around 1⁄4 and 1⁄3 of a year, and HD 34445 f was not detected.

The HD 34445 planetary system
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius
e (unconfirmed) ≥0.0529 ± 0.0089 MJ 0.2687 ± 0.0019 49.175 ± 0.045 0.090 ± 0.062 — —
d (unconfirmed) ≥0.097 ± 0.13 MJ 0.4817 ± 0.0033 117.87 ± 0.18 0.027 ± 0.051 — —
c (unconfirmed) ≥0.168 ± 0.016 MJ 0.7181 ± 0.0049 214.67 ± 0.45 0.036 ± 0.071 — —
f (unconfirmed) ≥0.119 ± 0.021 MJ 1.543 ± 0.016 676.8 ± 7.9 0.031 ± 0.057 — —
b ≥0.629 ± 0.028 MJ 2.075 ± 0.016 1056.7 ± 4.7 0.014 ± 0.035 — —
g (unconfirmed) ≥0.38 ± 0.13 MJ 6.36 ± 1.02 5700 ± 1500 0.032 ± 0.080 — —

See also

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. ^ Vogt, Steven S.; et al. (2017). "A Six-planet System around the Star HD 34445". The Astronomical Journal. 154 (5): 181. arXiv:1710.07337. Bibcode:2017AJ....154..181V. doi:10.3847/1538-3881/aa8b61. S2CID 119182115.
  3. ^ Soubiran, C.; et al. (2013). "The catalogue of radial velocity standard stars for Gaia. I. Pre-launch release". Astronomy and Astrophysics. 552. A64. arXiv:1302.1905. Bibcode:2013A&A...552A..64S. doi:10.1051/0004-6361/201220927. S2CID 56094559.
  4. ^ Sousa, S. G.; et al. (November 2006). "Spectroscopic parameters for a sample of metal-rich solar-type stars". Astronomy and Astrophysics. 458 (3): 873–880. Bibcode:2006A&A...458..873S. doi:10.1051/0004-6361:20065658.
  5. ^ Howard, Andrew W.; et al. (2010). "The California Planet Survey. I. Four New Giant Exoplanets". The Astrophysical Journal. 721 (2): 1467–1481. arXiv:1003.3488. Bibcode:2010ApJ...721.1467H. doi:10.1088/0004-637X/721/2/1467. S2CID 14147776.
  6. ^ Rosenthal, Lee J.; Fulton, Benjamin J.; Hirsch, Lea A.; Isaacson, Howard T.; Howard, Andrew W.; Dedrick, Cayla M.; Sherstyuk, Ilya A.; Blunt, Sarah C.; Petigura, Erik A.; Knutson, Heather A.; Behmard, Aida; Chontos, Ashley; Crepp, Justin R.; Crossfield, Ian J. M.; Dalba, Paul A.; Fischer, Debra A.; Henry, Gregory W.; Kane, Stephen R.; Kosiarek, Molly; Marcy, Geoffrey W.; Rubenzahl, Ryan A.; Weiss, Lauren M.; Wright, Jason T. (2021). "The California Legacy Survey. I. A Catalog of 178 Planets from Precision Radial Velocity Monitoring of 719 Nearby Stars over Three Decades". The Astrophysical Journal Supplement Series. 255 (1): 8. arXiv:2105.11583. Bibcode:2021ApJS..255....8R. doi:10.3847/1538-4365/abe23c. S2CID 235186973.
  7. ^ "HD 34445". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 19 November 2017.
  8. ^ 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.
  9. ^ Georgakarakos, Nikolaos; Dobbs-Dixon, Ian (September 2019). "Do the planets in the HD 34445 system really exist?". Monthly Notices of the Royal Astronomical Society. 488 (3): 3818–3825. arXiv:1907.05495. Bibcode:2019MNRAS.488.3818G. doi:10.1093/mnras/stz1945.


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