G 240-72

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G 240-72
Draco constellation map.svg
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G 240-72
Location of G 240-72 in the constellation Draco

Observation data
Epoch J2000        Equinox J2000
Constellation Draco
Right ascension 17h 48m 07.99282s [1]
Declination +70° 52′ 35.9221″ [1]
Apparent magnitude  (V)14.15 [2]
Characteristics
Spectral type DQP9.0 [2]
Apparent magnitude  (B)14.55 [3]
Apparent magnitude  (V)14.15 [3]
Apparent magnitude  (R)13.5 [3]
Apparent magnitude  (I)13.1 [3]
Apparent magnitude  (J)12.709 ± 0.021 [3]
Apparent magnitude  (H)12.528 ± 0.023 [3]
Apparent magnitude  (K)12.507 ± 0.023 [3]
Astrometry
Proper motion (μ)RA: -1266.387 mas/yr [1]
Dec.: 1108.801 mas/yr [1]
Parallax (π)160.9952±0.0119  mas [1]
Distance 20.259 ± 0.001  ly
(6.2114 ± 0.0005  pc)
Absolute magnitude  (MV)15.23 [2] [4] [note 1]
Details
Mass 0.81 ± 0.01 [2]   M☉
Radius 0.00984 [2] [note 2]   R☉
Luminosity 0.000085 [5]   L☉
Surface gravity (log g)8.36 ± 0.02 [2]   cgs
Temperature 5590 ± 90 [2]   K
Rotation >100 years [6]
Age 5.69 [note 3] [7]   Gyr
Other designations
GJ 1221, EG GR 372, G 240-72, LHS 455, LP 44-113, NLTT 45565, WD 1748+708, 2MASS J17480817+7052353 [3]
Database references
SIMBAD data

G 240-72 (or WD 1748+708, or LHS 455, or GJ 1221) is a nearby degenerate star (white dwarf) of spectral class DQP9.0, [2] located 20.3 light-years away in the constellation Draco.

Contents

Distance

G 240-72 is the seventh closest white dwarf (after Sirius B, Procyon B, van Maanen's star, Gliese 440, 40 Eridani B and Stein 2051 B). Its trigonometric parallax, as measured by the Gaia space telescope, is 160.9952±0.0119  mas , [1] corresponding to a distance of 6.2114 parsecs (20.259 light-years ).

Properties

G 240-72 has a mass of 0.81 Solar masses [2] and surface gravity 108.36 (2.29 · 108) cm·s−2, [2] or approximately 234 000 of Earth's, corresponding to a radius 6850 km, or 107% of Earth's.

This white dwarf has a relatively low temperature of 5590 K [2] (slightly cooler than the Sun), and an old cooling age, i.e. the age as a degenerate star (not counting the duration of its previous existence as a main sequence and giant star) of 5.69 Gyr. [7] It has a white appearance, due to its similar temperature to the Sun. It has a pure helium atmosphere and rotates very slowly, with period of possibly over 100 years. [6]

References

  1. 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.
  2. 1 2 3 4 5 6 7 8 9 10 11 Holberg, J. B.; Sion; Oswalt; McCook; Foran; Subasavage (2008). "A New Look at the Local White Dwarf Population" . The Astronomical Journal . 135 (4): 1225–1238. Bibcode:2008AJ....135.1225H. doi:10.1088/0004-6256/135/4/1225. S2CID   122855486.
  3. 1 2 3 4 5 6 7 8 "GJ 1221 -- White Dwarf". Centre de Données astronomiques de Strasbourg . Retrieved 2011-10-23.
  4. ↑ Van Altena, W. F.; Lee, J. T.; Hoffleit, E. D. (1995). GCTP 2835.01. The General Catalogue of Trigonometric Stellar Parallaxes (Fourth ed.). Bibcode:1995gcts.book.....V.
  5. ↑ Giammichele, N.; Bergeron, P.; Dufour, P. (April 2012). "Know Your Neighborhood: A Detailed Model Atmosphere Analysis of Nearby White Dwarfs". The Astrophysical Journal Supplement. 199 (2): 29. arXiv: 1202.5581 . Bibcode:2012ApJS..199...29G. doi:10.1088/0067-0049/199/2/29. S2CID   118304737.
  6. 1 2 Brinkworth, Carolyn S.; Burleigh, Matthew R.; Lawrie, Katherine; Marsh, Thomas R.; Knigge, Christian (August 2013). "Measuring the Rotational Periods of Isolated Magnetic White Dwarfs". The Astrophysical Journal . 773 (1): 47. Bibcode:2013ApJ...773...47B. doi:10.1088/0004-637X/773/1/47. ISSN   0004-637X.
  7. 1 2 Sion, Edward M.; Holberg, J. B.; Oswalt, Terry D.; McCook, George P.; Wasatonic, Richard (2009). "The White Dwarfs within 20 Parsecs of the Sun: Kinematics and Statistics". The Astronomical Journal . 138 (6): 1681–1689. arXiv: 0910.1288 . Bibcode:2009AJ....138.1681S. doi:10.1088/0004-6256/138/6/1681. S2CID   119284418.

Notes

  1. ↑ From apparent magnitude and parallax.
  2. ↑ From surface gravity and mass.
  3. ↑ Cooling age, i. e. age as degenerate star (not counting duration of previous existence as main sequence star and as giant star)
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