Ross 640

Ross 640
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Hercules
Right ascension 16h 28m 25.0031s[1]
Declination +36° 46′ 15.847″[1]
Apparent magnitude (V) 13.83[2]
Characteristics
Evolutionary stage white dwarf
Spectral type DZA5.5[3]
Astrometry
Proper motion (μ) RA: −494.230(15) mas/yr[1]
Dec.: 746.698(18) mas/yr[1]
Parallax (π)62.9109 ± 0.0143 mas[1]
Distance51.84 ± 0.01 ly
(15.895 ± 0.004 pc)
Absolute magnitude (MV)+13.01[4]
Details
Mass0.58±0.03[5] M☉
Luminosity0.0007[5] L☉
Surface gravity (log g)7.76[6] cgs
Temperature8,100[7] K
Age1.02[6] Gyr
Other designations
GJ 9564, LTT 14906, WD 1626+368[8]
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,[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.

  1. ^ a b c d e Cite error: The named reference Gaia DR3 was invoked but never defined (see the help page).
  2. ^ a b Cite error: The named reference Bergeron2001 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference Wesemael1993 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference limoges2015 was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference toonen2017 was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference holberg2016 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference Blouin2018 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Zeidler1986 was invoked but never defined (see the help page).