Astronomy:Ross 640
Coordinates: 
16h 28m 25.00s, +36° 46′ 15.9″
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Hercules |
| Right ascension | 16h 28m 25.00303s[1] |
| Declination | +36° 46′ 15.8492″[1] |
| Apparent magnitude (V) | 13.83[2] |
| Characteristics | |
| Evolutionary stage | white dwarf |
| Spectral type | DZA5.5[3] |
| Astrometry | |
| Proper motion (μ) | RA: −494.185[1] mas/yr Dec.: +746.554[1] mas/yr |
| Parallax (π) | 62.9147 ± 0.0223[1] mas |
| Distance | 51.84 ± 0.02 ly (15.895 ± 0.006 pc) |
| Absolute magnitude (MV) | +13.01[4] |
| Details | |
| Mass | 0.58±0.03[5] M☉ |
| Luminosity | 0.0007[5] L☉ |
| Surface gravity (log g) | 7.76[6] cgs |
| Temperature | 8,100[7] K |
| Age | 1.02[6] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
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,[2] it is too faint to be visible to the naked eye. Its trigonometric parallax from the Gaia mission is 62.9″,[1] 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.[3] 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.[7] Ross 640 has a spectrum characterized by hydrogen Balmer lines in the visible and very strong ionized magnesium lines in the ultraviolet.[9] The presence of heavy elements in the photosphere of Ross 640 indicates that it recently accreted rocky debris from its planetary system.
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G. Gaia DR2 record for this source at VizieR.
- ↑ 2.0 2.1 Bergeron, P.; Leggett, S. K.; Ruiz, María Teresa (2001). "Photometric and Spectroscopic Analysis of Cool White Dwarfs with Trigonometric Parallax Measurements" (in en). The Astrophysical Journal Supplement Series 133 (2): 413–450. doi:10.1086/320356. ISSN 0067-0049. Bibcode: 2001ApJS..133..413B.
- ↑ 3.0 3.1 Wesemael, F. et al. (1993). "An atlas of optical spectra of white-dwarf stars". Publications of the Astronomical Society of the Pacific 105: 761. doi:10.1086/133228. Bibcode: 1993PASP..105..761W.
- ↑ Limoges, M. -M; Bergeron, P.; Lépine, 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. doi:10.1088/0067-0049/219/2/19. Bibcode: 2015ApJS..219...19L.
- ↑ 5.0 5.1 Toonen, S.; Hollands, M.; Gänsicke, B. T.; Boekholt, T. (2017). "The binarity of the local white dwarf population". Astronomy and Astrophysics 602: A16. doi:10.1051/0004-6361/201629978. Bibcode: 2017A&A...602A..16T.
- ↑ 6.0 6.1 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. doi:10.1093/mnras/stw1357. Bibcode: 2016MNRAS.462.2295H.
- ↑ 7.0 7.1 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. doi:10.3847/1538-4357/aad4a9. Bibcode: 2018ApJ...863..184B.
- ↑ "ross 640". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=ross+640.
- ↑ 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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