HD 196917

HD 196917
Location of HD 196917 on the map (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Microscopium
Right ascension 20h 41m 23.65766s[1]
Declination −31° 35′ 53.8334″[1]
Apparent magnitude (V) 5.74[2] (5.75 - 5.76)[3]
Characteristics
Evolutionary stage AGB[4]
Spectral type M1 III[5] or M0 III[6]
B−V color index +1.53[7]
Variable type suspected[8]
Astrometry
Radial velocity (Rv)−97.3±2.3[9] km/s
Proper motion (μ) RA: +109.914 mas/yr[1]
Dec.: −60.256 mas/yr[1]
Parallax (π)7.6563 ± 0.0891 mas[1]
Distance426 ± 5 ly
(131 ± 2 pc)
Absolute magnitude (MV)+0.04[10]
Details
Mass1.27[11] M☉
Radius44.2±2.2[12] R☉
Luminosity620+45
−20[1] L☉
Surface gravity (log g)1.40[11] cgs
Temperature3,908±122[13] K
Metallicity [Fe/H]−0.28[11] dex
Other designations
17 G. Microscopii[14], NSV 25227, CD−32°16130, CPD−32°6177, FK5 3652, GC 28808, HD 196917, HIP 102092, HR 7909, SAO 212345, TIC 441396067[15]
Database references
SIMBADdata

HD 196917 (HR 7909; 17 G. Microscopii; NSV 25227) is a solitary star[16] located in the southern constellation Microscopium. It is faintly visible to the naked eye as a red-hued point of light with an apparent magnitude of 5.74.[2] Gaia DR3 parallax measurements imply a distance of 426 light-years and[1] it is rapidly approaching the Solar System with a heliocentric radial velocity of −97.3 km/s.[9] At its current distance, HD 196917's brightness is diminished by 0.13 magnitudes due to interstellar extinction[17] and it has an absolute magnitude of +0.04.[10]

HD 196917 has a stellar classification of either M1 III[5] or M0 III,[6] indicating that it is an evolved M-type giant. It is currently on the asymptotic giant branch,[4] fusing hydrogen and helium shells around an inert carbon core. It has 1.27 times the mass of the Sun[11] but it has expanded to 44.2 times the radius of the Sun.[12] It radiates 620 times the luminosity of the Sun[1] from its enlarged photosphere at an effective temperature of 3,908 K.[13] HD 196917 is metal deficient with an iron abundance of [Fe/H] = −0.28 or 52.5% of the Sun's.[11]

The variability of the star was first detected in 1997 by the Hipparcos mission.[18] It found variations between 5.82 and 5.86 in the Hipparcos passband. Koen & Lyer (2002) observed visual variations from the star and found that HD 196917 varies by 0.009 magnitudes within 21.01 hours.[19] As of 2004, its variability has not been confirmed.[20]

  1. ^ a b c d e f g Cite error: The named reference GaiaDR3 was invoked but never defined (see the help page).
  2. ^ a b Cite error: The named reference Tycho2000 was invoked but never defined (see the help page).
  3. ^ Cite error: The named reference VSX was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Eggen1992 was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference Houk1982 was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference Evans1957 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference Johnson1966 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference Samus2017 was invoked but never defined (see the help page).
  9. ^ a b Cite error: The named reference Gontcharov2006 was invoked but never defined (see the help page).
  10. ^ a b Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).
  11. ^ a b c d e Cite error: The named reference Anders2019 was invoked but never defined (see the help page).
  12. ^ a b Cite error: The named reference Kervella2004 was invoked but never defined (see the help page).
  13. ^ a b Cite error: The named reference Stassun2019 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference Gould1879 was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  16. ^ Cite error: The named reference Eggleton2008 was invoked but never defined (see the help page).
  17. ^ Cite error: The named reference Gontcharov2017 was invoked but never defined (see the help page).
  18. ^ Cite error: The named reference Perryman1997 was invoked but never defined (see the help page).
  19. ^ Cite error: The named reference Koen2002 was invoked but never defined (see the help page).
  20. ^ Cite error: The named reference Samus2004 was invoked but never defined (see the help page).