Upsilon2 Cassiopeiae

For other star systems with this Bayer designation, see υ Cassiopeiae
υ2 Cassiopeiae

Map of the Bayer-designated stars in Cassiopeia. Upsilon2 Cassiopeiae is circled.
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cassiopeia
Right ascension 00h 56m 39.90413s[1]
Declination +59° 10′ 51.8006″[1]
Apparent magnitude (V) +4.62[2]
Characteristics
Evolutionary stage horizontal branch[3]
Spectral type G8 IIIb Fe−0.5[4]
U−B color index +0.68[2]
B−V color index +0.96[2]
Astrometry
Radial velocity (Rv)−47.73±0.12[5] km/s
Proper motion (μ) RA: −92.085[1] mas/yr
Dec.: −45.079[1] mas/yr
Parallax (π)17.2875 ± 0.1880 mas[1]
Distance189 ± 2 ly
(57.8 ± 0.6 pc)
Absolute magnitude (MV)+0.62[6]
Details[5]
Mass1.44±0.16 M☉
Radius10.44+0.24
−0.50[1] R☉
Luminosity55.3±0.7[1] L☉
Surface gravity (log g)2.75±0.19 cgs
Temperature4,937±14 K
Metallicity [Fe/H]−0.35±0.03 dex
Rotational velocity (v sin i)0.54±0.38 km/s
Age2.20±0.62 Gyr
Other designations
Castula, υ2 Cas, 28 Cassiopeiae, BD+58° 138, HD 5395, HIP 4422, HR 265, SAO 21855
Database references
SIMBADdata

Upsilon2 Cassiopeiae, Latinised from υ2 Cassiopeiae, is a solitary star in the constellation of Cassiopeia, a few degrees to the south of Gamma Cassiopeiae. It has the proper name Castula /ˈkæstjʊlə/, which has been officially adopted by the IAU.[7] The star has a yellow hue and is faintly visible to the naked eye with an apparent visual magnitude of +4.62.[2] Based upon parallax measurements, it is located at a distance of approximately 189 light years from the Sun.[1] The star is drifting closer with a radial velocity of −48 km/s.[5]

This is an aging giant star with a stellar classification of G8 IIIb Fe−0.5,[4] where the suffix notation indicates a mild underabundance of iron in the spectrum. With the supply of core hydrogen exhausted, this star has cooled and expanded off the main sequence – at present it has 10[1] times the girth of the Sun. It is a red clump giant, which means it is on the horizontal branch undergoing core helium fusion.[3]

Upsilon2 Cassiopeiae is a barium star, showing an excess of the element barium in its spectrum. This can occur from mass transfer from a more-evolved companion star that later became a white dwarf, although no companion has been detected.[6] It is 2.2 billion years old with 1.44 times the mass of the Sun.[5] The star is radiating 55[1] times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,937 K.[5]

  1. ^ a b c d e f g h i j 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 Argue1966 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference Puzeras2010 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference perkins1989 was invoked but never defined (see the help page).
  5. ^ a b c d e Cite error: The named reference Jofre2015 was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference Bergeat1997 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference IAU-LSN was invoked but never defined (see the help page).