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  • 21 Aug, 2019

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HD 42936
HD 42936, also known as DMPP-3, is a star located in the southern circumpolar constellation Mensa. With an apparent magnitude of 9.1, it is too faint to be detected with the naked eye but can be seen with a telescope. The star is relatively close at a distance of about 153 light-years (47 parsecs) but is receding with a heliocentric radial velocity of 35.6 km/s.

HD 42936 is an early K-type star with the blended luminosity class of a main sequence star and a subgiant. At present it has 87% the mass of the Sun and 91% the radius of the Sun. The object shines at 51% the luminosity of the Sun from its photosphere at an effective temperature of 5,138 K, which gives it an orangish yellow glow. HD 42936 has iron abundance 151% that of the Sun, meaning it is metal enriched despite an age of 10.9 billion years.

HD 42936 has a very low mass companion star in a close orbit, approaching to 0.498 AU at periastron.

Planetary system

In 2019, a radial velocity analysis carried out by a team of astronomers led by astronomer John R. Barnes of the Dispersed Matter Planet Project (DMPP) confirmed the existence of a super-Earth in orbit around DMPP-3 A. Planets in close binary star systems such as this are rare.

A follow-up study in 2023 refined the parameters of the planet and companion star, and detected two additional radial velocity signals. One of these could be caused by a second, Earth-mass planet closer to the star, but the other, 800-day signal cannot be caused by an orbiting body because the companion star would make its orbit unstable. The study concludes that the 800-day signal must be caused by stellar activity, but if not for the companion star it could have been considered a likely planet, which has implications for other radial velocity planet detections.

The DMPP-3 A planetary system
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius
c (unconfirmed) ≥1.065+0.173
−0.259 M🜨 		0.033+0.002
−0.0001 		2.26+0.20
−0.10 		0 — —
b ≥2.22+0.50
−0.28 M🜨 		0.0670+0.0003
−0.0002 		6.6732+0.0011
−0.0003 		0.174+0.032
−0.084 		— —

See also

References

  1. ^ 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. ^ Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331–346. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. ISSN 1063-7737. S2CID 255204555.
  3. ^ Houk, N.; Cowley, A. P. (1975). University of Michigan Catalogue of two-dimensional spectral types for the HD stars. Volume I. Declinations -90_ to -53_ƒ0. Bibcode:1975mcts.book.....H.
  4. ^ Cousins, A. W. J.; Stoy, R. H. (1962). "Photoelectric magnitudes and colours of Southern stars". Royal Greenwich Observatory Bulletins. 64: 103. Bibcode:1962RGOB...64..103C.
  5. ^ Haswell, Carole A.; Staab, Daniel; Barnes, John R.; Anglada-Escudé, Guillem; Fossati, Luca; Jenkins, James S.; Norton, Andrew J.; Doherty, James P. J.; Cooper, Joseph (2019). "Dispersed Matter Planet Project discoveries of ablating planets orbiting nearby bright stars". Nature Astronomy. 4 (4): 408–418. arXiv:1912.10874. doi:10.1038/s41550-019-0973-y. S2CID 209444484.
  6. ^ Stevenson, Adam T.; Haswell, Carole A.; et al. (May 2023). "DMPP-3: confirmation of short-period S-type planet(s) in a compact eccentric binary star system, and warnings about long-period RV planet detections". Monthly Notices of the Royal Astronomical Society. arXiv:2305.06263.
  7. ^ 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.
  8. ^ Barnes, John R.; Haswell, Carole A.; Staab, Daniel; Anglada-Escudé, Guillem; Fossati, Luca; Doherty, James P. J.; Cooper, Joseph; Jenkins, James S.; Díaz, Matías R.; Soto, Maritza G.; Peña Rojas, Pablo A. (2019). "An ablating 2.6-M🜨 planet in an eccentric binary from the Dispersed Matter Planet Project". Nature Astronomy. 4 (4): 419–426. arXiv:1912.10793. doi:10.1038/s41550-019-0972-z. S2CID 209444780.
  9. ^ HD 42936, entry, SIMBAD. Accessed online December 24, 2019.
  10. ^ Jenkins, J. S.; Jones, H. R. A.; Pavlenko, Y.; Pinfield, D. J.; Barnes, J. R.; Lyubchik, Y. (July 2008). "Metallicities and activities of southern stars". Astronomy & Astrophysics. 485 (2): 571–584. arXiv:0804.1128. Bibcode:2008A&A...485..571J. doi:10.1051/0004-6361:20078611. ISSN 0004-6361.



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