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Ross 640

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Coordinates: Sky map 16h 28m 25.00s, +36° 46â€ē 15.9â€ģ
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Ross 640
Observation data
Epoch J2000.0      Equinox ICRS
Constellation Hercules[1]
Right ascension 16h 28m 25.0031s[2]
Declination +36° 46â€ē 15.847â€ģ[2]
Apparent magnitude (V) 13.83[3]
Characteristics
Evolutionary stage white dwarf
Spectral type DZA5.5[4]
Astrometry
Proper motion (ξ) RA: −494.230(15) mas/yr[2]
Dec.: 746.698(18) mas/yr[2]
Parallax (π)62.9109Âą0.0143 mas[2]
Distance51.84 ¹ 0.01 ly
(15.895 ¹ 0.004 pc)
Absolute magnitude (MV)+13.01[5]
Details
Mass0.58±0.03[6] M☉
Luminosity0.0007[6] L☉
Surface gravity (log g)7.76[7] cgs
Temperature8,100[8] K
Age1.02[7] Gyr
Other designations
GJ 626.2, GJ 9564, LTT 14906, WD 1626+368[9]
Database references
SIMBADdata

Ross 640 is a white dwarf star in the northern constellation of Hercules, positioned near the constellation border with Corona Borealis. With an apparent visual magnitude of 13.83,[3] it is too faint to be visible to the naked eye. Its trigonometric parallax from the Gaia mission is 62.9â€ģ,[2] corresponding to a distance of 52 light-years (15.9 parsecs).

This compact star has a stellar classification of DZA5.5, indicating a metal-rich atmosphere accompanied by weaker lines of hydrogen.[4] A detailed analysis of its spectrum revealed that Ross 640 is a relatively cool white dwarf with an effective temperature of approximately 8,100 K, which means that it has been in the white dwarf phase for slightly more than 1 billion years.[8] Ross 640 has a spectrum characterized by hydrogen Balmer lines in the visible and very strong ionized magnesium lines in the ultraviolet.[10] The presence of heavy elements in the photosphere of Ross 640 indicates that it recently accreted rocky debris from its planetary system.

References

[edit]
  1. ↑ Roman, Nancy G. (1987). "Identification of a constellation from a position". Publications of the Astronomical Society of the Pacific. 99 (617): 695. Bibcode:1987PASP...99..695R. doi:10.1086/132034. Constellation record for this object at VizieR.
  2. 1 2 3 4 5 6 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.
  3. 1 2 Bergeron, P.; Leggett, S. K.; Ruiz, María Teresa (2001). "Photometric and Spectroscopic Analysis of Cool White Dwarfs with Trigonometric Parallax Measurements". The Astrophysical Journal Supplement Series. 133 (2): 413–450. arXiv:astro-ph/0011286. Bibcode:2001ApJS..133..413B. doi:10.1086/320356. ISSN 0067-0049. S2CID 15511301.
  4. 1 2 Wesemael, F.; et al. (1993). "An atlas of optical spectra of white-dwarf stars". Publications of the Astronomical Society of the Pacific. 105: 761. Bibcode:1993PASP..105..761W. doi:10.1086/133228. S2CID 122605705.
  5. ↑ Limoges, M. -M; Bergeron, P.; LÃĐpine, S. (2015). "Physical Properties of the Current Census of Northern White Dwarfs within 40 pc of the Sun". The Astrophysical Journal Supplement Series. 219 (2): 19. arXiv:1505.02297. Bibcode:2015ApJS..219...19L. doi:10.1088/0067-0049/219/2/19. S2CID 118494290.
  6. 1 2 Toonen, S.; Hollands, M.; GÃĪnsicke, B. T.; Boekholt, T. (2017). "The binarity of the local white dwarf population". Astronomy and Astrophysics. 602: A16. arXiv:1703.06893. Bibcode:2017A&A...602A..16T. doi:10.1051/0004-6361/201629978. S2CID 12367523.
  7. 1 2 Holberg, J. B.; Oswalt, T. D.; Sion, E. M.; McCook, G. P. (2016). "The 25 parsec local white dwarf population". Monthly Notices of the Royal Astronomical Society. 462 (3): 2295. arXiv:1606.01236. Bibcode:2016MNRAS.462.2295H. doi:10.1093/mnras/stw1357. hdl:10150/621732.
  8. 1 2 Blouin, S.; Dufour, P.; Allard, N. F. (23 August 2018). "A New Generation of Cool White Dwarf Atmosphere Models. I. Theoretical Framework and Applications to DZ Stars". The Astrophysical Journal. 863 (2): 184. arXiv:1807.06616. Bibcode:2018ApJ...863..184B. doi:10.3847/1538-4357/aad4a9. S2CID 119347098.
  9. ↑ "ross 640". SIMBAD. Centre de donnÃĐes astronomiques de Strasbourg. Retrieved 2019-08-20.
  10. ↑ Zeidler-K.T., E.-M.; Weidemann, V.; Koester, D. (1986). "Metal abundances in helium-rich white dwarf atmospheres". Astronomy & Astrophysics. 155 (2): 356–370. Bibcode:1986A&A...155..356Z.
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