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HD 42936

HD 42936

Location of HD 42936 in the night sky. The star is marked within the red diamond.
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Mensa
Right ascension 06h 06m 29.84725s[1]
Declination −72° 30′ 45.5674″[1]
Apparent magnitude (V) 9.10[2]
Characteristics
HD 42936A
Evolutionary stage main sequence star
Spectral type K0 IV/V[3]
B−V color index +0.91[4]
HD 42936B
Evolutionary stage main sequence star
Spectral type L[5]
Astrometry
Radial velocity (Rv)35.64±0.49[1] km/s
Proper motion (μ) RA: −0.716 mas/yr[1]
Dec.: −382.755 mas/yr[1]
Parallax (π)21.2496 ± 0.1143 mas[1]
Distance153.5 ± 0.8 ly
(47.1 ± 0.3 pc)
Absolute magnitude (MV)5.78[2]
Orbit[6]
PrimaryHD 42936A
CompanionHD 42936B
Period (P)506.89±0.01 d
Semi-major axis (a)1.139±0.004 AU
Eccentricity (e)0.596±0.001
Inclination (i)63.89±0.78°
Argument of periastron (ω)
(secondary)		158.88+0.03
−0.01°
Semi-amplitude (K1)
(primary)		2.65731+0.00033
−0.00002 km/s
Details[6]
HD 42936A
Mass0.900±0.009 M☉
Radius0.861±0.005 R☉
Luminosity0.510±0.003[7] L☉
Surface gravity (log g)4.266±0.045 cgs
Temperature5,201±20 K
Metallicity [Fe/H]0.147±0.013 dex
Rotation21.8+0.5
−16.5 d[8]
Rotational velocity (v sin i)3.17±0.1 km/s
Age9.6±0.8 Gyr
HD 42936B
Mass91.90±0.85 MJup
Other designations
DMPP-3, CD−72°312, CPD−72°451, GC 7845, HD 42936, HIP 28941, SAO 256269[9]
Database references
SIMBADdata
Exoplanet Archivedata

HD 42936, also known as DMPP-3, is a star located in the southern circumpolar constellation Mensa. With an apparent magnitude of 9.1,[2] 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.[1]

HD 42936 is an early K-type star with the blended luminosity class of a main sequence star and a subgiant.[3] At present it has 87% the mass of the Sun and 91% the radius of the Sun.[8] The object shines at 51% the luminosity of the Sun[7] from its photosphere at an effective temperature of 5,138 K,[8] which gives it an orangish yellow glow. HD 42936 has iron abundance 151% that of the Sun, meaning it is metal enriched[10] despite an age of 10.9 billion years.[8]

HD 42936 has a very low mass companion star in a close orbit,[8] approaching to 0.498 AU at periastron.[6]

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.[8]

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.[6]

The DMPP-3 A planetary system[6]
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[8] 		0.174+0.032
−0.084 		— —

See also

References

  1. ^ a b c d e f 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. ^ a b c 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. ^ a b 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. ^ a b c d e 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. ^ a b 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. ^ a b c d e f g 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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