HD 165634

HD 165634
Location of HD 165634 (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Sagittarius
Right ascension 18h 08m 04.97982s[1]
Declination −28° 27′ 25.5316″[1]
Apparent magnitude (V) 4.56[2]
Characteristics
Spectral type G7:IIIb CN−1 CH−3.5 HK+1[3]
U−B color index +0.75[2]
B−V color index +0.95[2]
Astrometry
Radial velocity (Rv)−4.87[4] km/s
Proper motion (μ) RA: +25.43[1] mas/yr
Dec.: −31.18[1] mas/yr
Parallax (π)9.62 ± 0.26 mas[1]
Distance339 ± 9 ly
(104 ± 3 pc)
Absolute magnitude (MV)−0.53[5]
Details[6]
Mass3.38 M☉
Radius16.98 R☉
Luminosity168 L☉
Surface gravity (log g)2.51 cgs
Temperature5,043 K
Metallicity [Fe/H]−0.05 dex
Rotational velocity (v sin i)2.6[7] km/s
Other designations
CD−28°14174, FK5 3439, GC 24694, HD 165634, HIP 88839, HR 6766, SAO 186328, GSC 06854-04372[8]
Database references
SIMBADdata

HD 165634 is a star in the southern constellation of Sagittarius. It has a yellow hue and is faintly visible to the naked eye with apparent visual magnitude of 4.56.[2] The star is located at a distance of approximately 339 light years from the Sun based on parallax,[1] but is drifting closer with a radial velocity of −5 km/s.[4] It has an absolute magnitude of −0.53.[5]

This is a CH-peculiar[9] giant star with a stellar classification of G7:IIIbCN-1CH-3.5HK+1, and has been designated as a standard example of this spectral type.[3] This notation indicates a G-type giant (G7:IIIb) with underabundances of CN and CH molecules. It is a rare "weak G–band star", showing an abnormally weak G band of the molecule CN. This indicates an underabundance of carbon in the stellar atmosphere; the abundances of most other elements are otherwise normal for a star at its evolutionary stage.[10] The depletion of carbon is a reflection of internal processes while the star is on the red giant branch, accompanied by deep mixing.[11]

In 2000, Böhm-Vitense and collaborators suggested that the star has an evolved white dwarf companion. This object can explain an excess flux of ultraviolet radiation, and a mass-transfer could be the source for a mild nitrogen excess on the visible component. The progenitor star was not very evolved because there is no excess of s-process elements such as barium. It may even have been a low-mass star that lost its envelope.[9]

  1. ^ a b c d e f Cite error: The named reference vanLeeuwen2007 was invoked but never defined (see the help page).
  2. ^ a b c d Cite error: The named reference Ducati2002 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference Keenan_McNeil_1989 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference APJSS141 was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference XHIP was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference Reffert2015 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference deMedeiros2014 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. ^ a b Cite error: The named reference Böhm-Vitense_et_al_2000 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference sneden_et_al_1978 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Palacios_et_al_2012 was invoked but never defined (see the help page).