Delta Aurigae

Delta Aurigae
Location of δ Aurigae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Auriga
Right ascension 05h 59m 31.61842s[1]
Declination +54° 17′ 05.0567″[1]
Apparent magnitude (V) 3.715[2]
Characteristics
Spectral type K0 IIIb[3]
U−B color index +0.837[2]
B−V color index +1.017[2]
R−I color index 0.5
Astrometry
Radial velocity (Rv)+9.75±0.44[4] km/s
Proper motion (μ) RA: +85.814[1] mas/yr
Dec.: −142.928[1] mas/yr
Parallax (π)23.0557 ± 0.4512 mas[1]
Distance141 ± 3 ly
(43.4 ± 0.8 pc)
Absolute magnitude (MV)0.56[5]
Orbit[6]
Period (P)1,283.4±0.7 d
Semi-major axis (a)≥ 39.1 ± 0.8 Gm (0.2614 ± 0.0053 AU)
Eccentricity (e)0.231±0.017
Periastron epoch (T)52,980±16 MJD
Argument of periastron (ω)
(secondary)		200±5°
Semi-amplitude (K1)
(primary)		2.28±0.04 km/s
Details
Mass1.63[7] M☉
Radius11[8] R☉
Luminosity62[8] L☉
Surface gravity (log g)2.7[8] cgs
Temperature4,786[8] K
Metallicity [Fe/H]−0.15[8] dex
Rotational velocity (v sin i)3.9[8] km/s
Age3.26[7] Gyr
Other designations
δ Aur, 33 Aurigae, BD+54 970, FK5 225, HD 40035, HIP 28358, HR 2077, SAO 25502[9]
Database references
SIMBADdata

Delta Aurigae, Latinized from δ Aurigae, is the Bayer designation for an astrometric binary[10] star in the northern constellation of Auriga. It is visible to the naked eye with an apparent visual magnitude of 3.715.[2] Based upon its annual parallax shift of 23.06 mas,[1] it is some 141 light-years (43 parsecs) distant from the Earth, give or take a three light-year margin of error. It is drifting further away with a radial velocity of +10 km/s.[4] This star is the namesake for the Delta Aurigids, a meteor shower that occurs between October 6–15.[11] The radiant point for this shower passes several degrees to the south of the star.[12]

The variable radial velocity of this system was not recognized until 1999, more than a century following the first measurement in 1897. Delta Aurigae is a single-lined spectroscopic binary: periodic Doppler shifts in the star's spectrum indicate orbital motion. The pair have an orbital period of 1,283.4 days (3.514 years) and an eccentricity of 0.231. Based on the small amplitude of the radial velocity variation, the companion is most likely a small K- or early M-type main-sequence star with around half the mass of the Sun.[6]

The visible component of this system is an evolved giant star with a stellar classification of K0 IIIb.[3] It is a red clump star, indicating that it is generating energy through helium fusion at its core.[13] The star is 3.26[7] billion years old and is spinning with a projected rotational velocity of 4 km/s.[8] It has 1.63[7] times the mass of the Sun and has expanded to 11[8] times the Sun's radius. The star is radiating 62 times the Sun's luminosity[8] from the star's photosphere at an effective temperature of 4,786 K.[8] This heat gives the star the orange-hued glow of a K-type star.[14]

  1. ^ a b c d e f Cite error: The named reference GaiaDR2 was invoked but never defined (see the help page).
  2. ^ a b c d Cite error: The named reference aaass65_2_405 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 Massarotti_et_al_2008 was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference xhip was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference Griffin2009 was invoked but never defined (see the help page).
  7. ^ a b c d Cite error: The named reference Luck2015 was invoked but never defined (see the help page).
  8. ^ a b c d e f g h i j Cite error: The named reference aj135_1_209 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference mnras389_2_869 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference reynolds2010 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference lunsford was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference Alves2000 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference csiro was invoked but never defined (see the help page).