Upsilon1 Cassiopeiae

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

Upsilon¹ Cassiopeiae (υ¹ Cassiopeiae) is an astrometric binary^[9] star system in the northern constellation of Cassiopeia. It is visible to the naked eye with an apparent visual magnitude of 4.82.^[2] Based upon an annual parallax shift of 9.93 mas as seen from Earth,^[1] this system is located about 330 light years from the Sun.

υ¹ Cassiopeiae

Location of υ1 Cassiopeiae (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Cassiopeia
Right ascension	00h 55m 00.15523s[1]
Declination	+58° 58′ 21.7108″[1]
Apparent magnitude (V)	4.82[2]
Characteristics
Spectral type	K2 III[3]
U−B color index	+1.25[2]
B−V color index	+1.21[2]
Astrometry
Radial velocity (Rv)	−23.57[4] km/s
Proper motion (μ)	RA: −33.50±0.36[1] mas/yr Dec.: −40.82±0.33[1] mas/yr
Parallax (π)	9.93 ± 0.49 mas[1]
Distance	330 ± 20 ly (101 ± 5 pc)
Absolute magnitude (MV)	−0.644[4]
Details
Mass	1.39[5] M☉
Radius	21[6] R☉
Luminosity	174[5] L☉
Surface gravity (log g)	1.76[4] cgs
Temperature	4,422±14[5] K
Metallicity [Fe/H]	−0.25[4] dex
Rotational velocity (v sin i)	1.1[7] km/s
Age	4.75[5] Gyr
Other designations
υ1 Cas, 26 Cas, BD+58° 134, HD 5234, HIP 4292, HR 253, SAO 21832, ADS 748, CCDM J00551+5858, WDS J00550+5858A[8]
Database references
SIMBAD	data

υ¹ Cassiopeiae is the bright star in the lower right. The bright star in the upper left is υ² Cassiopeiae.

The visible component is an evolved K-type giant star with a stellar classification of K2 III.^[3] With an estimated age of 4.75 billion years,^[5] it is a red clump star that is generating energy through the fusion of helium at its core.^[10] The measured angular diameter, after correction for limb darkening, is 1.97±0.02 mas.^[11] At the estimated distance of the star, this yields a physical size of about 21 times the radius of the Sun.^[6] It has 1.39 times the mass of the Sun and is radiating 174 times the Sun's luminosity from its expanded photosphere at an effective temperature of 4,422 K.^[5]

There is a magnitude 12.50 visual companion at an angular separation of 17.80 arc seconds along a position angle of 61°, as of 2003. A more distant magnitude 12.89 companion lies at a separation of 93.30 arc seconds along a position angle of 125°, as measured in 2003. Neither star appears to be physically associated with υ¹ Cas.^[12]

References

1. van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
2. Argue, A. N. (1966), "UBV photometry of 550 F, G and K type stars", Monthly Notices of the Royal Astronomical Society, 133 (4): 475, Bibcode:1966MNRAS.133..475A, doi:10.1093/mnras/133.4.475.
3. Eggen, O. J. (1962), "Space-velocity vectors for 3483 stars with proper motion and radial velocity", Royal Observatory Bulletin, 51: 79, Bibcode:1962RGOB...51...79E.
4. Soubiran, C.; et al. (2008), "Vertical distribution of Galactic disk stars. IV. AMR and AVR from clump giants", Astronomy and Astrophysics, 480 (1): 91–101, arXiv:0712.1370, Bibcode:2008A&A...480...91S, doi:10.1051/0004-6361:20078788, S2CID 16602121.
5. Luck, R. Earle (September 2015), "Abundances in the Local Region. I. G and K Giants", The Astronomical Journal, 150 (3): 23, arXiv:1507.01466, Bibcode:2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88, S2CID 118505114, 88.
6. Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, vol. 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R_*) is given by:

   ${\displaystyle {\begin{aligned}2\cdot R_{*}&={\frac {(101\cdot 1.97\cdot 10^{-3})\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&\approx 42.8\cdot R_{\bigodot }\end{aligned}}}$

7. De Medeiros, J. R.; et al. (November 2000), "Rotation and lithium in single giant stars", Astronomy and Astrophysics, 363: 239–243, arXiv:astro-ph/0010273, Bibcode:2000A&A...363..239D.
8. "ups01 Cas". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-08-30.
9. Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
10. Valentini, M.; Munari, U. (November 2010), "A spectroscopic survey of faint, high-Galactic-latitude red clump stars. I. The high resolution sample", Astronomy and Astrophysics, 522: A79, arXiv:1007.0207, Bibcode:2010A&A...522A..79V, doi:10.1051/0004-6361/201014870, S2CID 119156545.^{[permanent dead link]}
11. Richichi, A.; et al. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431 (2): 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039.
12. Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122 (6): 3466, Bibcode:2001AJ....122.3466M, doi:10.1086/323920.