GP Comae Berenices

GP Comae Berenices, abbreviated to GP Com and also known as G 61-29, is a star system composed of a white dwarf orbited by a planetary mass object, likely the highly eroded core of another white dwarf star.[7] The white dwarf is slowly accreting material from its satellite at a rate of (3.5±0.5)×10−11 M☉/year and was proven[8] to be a low-activity AM CVn star.[7][6] The star system is showing signs of a high abundance of ionized nitrogen from the accretion disk around the primary.[9]

GP Comae Berenices

An ultraviolet band light curve for GP Comae Berenices, adapted from Smak (1975).[1] The error bar shown on the leftmost point applies to all points.
Observation data
Epoch J2000      Equinox J2000
Constellation Coma Berenices
Right ascension 13h 05m 42.40089s[2]
Declination +18° 01′ 03.7653″[2]
Apparent magnitude (V) 15.69[3]
Characteristics
Evolutionary stage White dwarf
Spectral type DBe[4]
Apparent magnitude (g) 15.929[5]
Variable type AM CVn
Astrometry
Proper motion (μ) RA: −344.92±0.06 mas/yr[5]
Dec.: 34.85±0.06 mas/yr[5]
Parallax (π)13.7306 ± 0.0452 mas[5]
Distance237.5 ± 0.8 ly
(72.8 ± 0.2 pc)
Details[6]
Mass0.59±0.09 M☉
Temperature14,800±500 K
Other designations
2MASS J13054243+1801039, G 61-29, LTT 18284, WD 1303+18, Gaia DR2 3938156295111047680
Database references
SIMBADdata

Planetary system

The material emitted from the planetary mass companion is mostly helium, with a molar ratio of nitrogen up to 1.7%, very low neon levels and other elements not detectable at all.[10] Approximately half of the luminosity of the system comes from the accretion disk.[6] The planetary object is suspected to contain a strange quark matter core due to its unusually high density, which must be above 187.5 g/cm3 to prevent tidal disruption; the theoretical bound for planets composed solely of ordinary matter is on the order of 30 g/cm3. The object's orbit is expected to decay within 100 million years due to gravitational wave emission.[11]

The GP Com planetary system[6]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(seconds)		 Eccentricity Inclination Radius
b 10.5±1.5 MJ 0.0014[11] 2794 0 59.5±14.5[9]° ≤ 0.420±0.020 RJ

References
  1. Smak, J. (January 1975). "The helium emission-line object G 61-29". Acta Astronomica. 25: 227–233. Bibcode:1975AcA....25..227S. Retrieved 12 December 2021.
  2. "G 61-29". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-12-09.
  3. Samus', N. N.; Kazarovets, E. V.; Durlevich, O. V.; Kireeva, N. N.; Pastukhova, E. N. (2017). "General catalogue of variable stars: Version GCVS 5.1". Astronomy Reports. 61 (1): 80. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. S2CID 125853869.
  4. Burbidge, E. M.; Strittmatter, P. A. (1971), "G61 - 29, a Helium Emission-Line Star", The Astrophysical Journal, 170: L39, Bibcode:1971ApJ...170L..39B, doi:10.1086/180836
  5. 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.
  6. Sion, Edward M.; Linnell, Albert P.; Godon, Patrick; Ballouz, Ronald-Louis (2011), "THE HOT COMPONENTS OF AM CVN HELIUM CATACLYSMICS", The Astrophysical Journal, 741 (1): 63, arXiv:1108.1388, Bibcode:2011ApJ...741...63S, doi:10.1088/0004-637X/741/1/63, S2CID 119284962
  7. Zhang, Xian-Fei; Liu, Jin-Zhong; Jeffery, C. Simon; Hall, Philip D.; Bi, Shao-Lan (2018), "The double helium-white dwarf channel for the formation of AM CVN binaries", Research in Astronomy and Astrophysics, 18 (1): 009, arXiv:1801.03196, Bibcode:2018RAA....18....9Z, doi:10.1088/1674-4527/18/1/9, S2CID 73586281
  8. Morales-Rueda, L.; Marsh, T. R.; Steeghs, D.; Unda-Sanzana, E.; Wood, J. H.; North, R. C. (2003), "New results on GP Com", Astronomy & Astrophysics, 405: 249–261, arXiv:astro-ph/0304265, Bibcode:2003A&A...405..249M, doi:10.1051/0004-6361:20030552, S2CID 119033361
  9. Kupfer, T.; Steeghs, D.; Groot, P. J.; Marsh, T. R.; Nelemans, G.; Roelofs, G. H. A. (2016), "UVES and X-Shooter spectroscopy of the emission line AM CVN systems GP Com and V396 Hya", Monthly Notices of the Royal Astronomical Society, 457 (2): 1828, arXiv:1601.02841, Bibcode:2016MNRAS.457.1828K, doi:10.1093/mnras/stw126
  10. Nelemans, G.; Yungelson, L. R.; Sluys, M. V. van der; Tout, Christopher A. (2009), "The chemical composition of donors in AM CVN stars and ultracompact X-ray binaries: Observational tests of their formation", Monthly Notices of the Royal Astronomical Society, 401 (2): 1347–1359, arXiv:0909.3376, doi:10.1111/j.1365-2966.2009.15731.x, S2CID 2716902
  11. Kuerban, Abudushataer; Geng, Jin-Jun; Huang, Yong-Feng; Zong, Hong-Shi; Gong, Hang (2020), "Close-in Exoplanets as Candidates for Strange Quark Matter Objects", The Astrophysical Journal, 890 (1): 41, arXiv:1908.11191, Bibcode:2020ApJ...890...41K, doi:10.3847/1538-4357/ab698b, S2CID 201671383
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