4 Vulpeculae

4 Vulpeculae is a single,^[7] orange-hued star in the northern constellation of Vulpecula. It forms part of the asterism, formerly thought to be an open cluster, called the coathanger or Brocchi's Cluster.^[8][9] The star is faintly visible to the naked eye with an apparent visual magnitude of 5.16.^[2] The distance to this star, based upon an annual parallax shift of 12.5320±0.1008 mas,^[1] is around 260 light years.

4 Vulpeculae

Observation data Epoch J2000      Equinox J2000
Constellation	Vulpecula
Right ascension	19h 25m 28.6030389750s[1]
Declination	+19° 47′ 54.059820728″[1]
Apparent magnitude (V)	5.16[2]
Characteristics
Spectral type	K0 III[2]
B−V color index	+0.980[2]
Astrometry
Radial velocity (Rv)	+0.95 ± 0.12[1] km/s
Proper motion (μ)	RA: +87.392 ± 0.137[1] mas/yr Dec.: -73.038 ± 0.152[1] mas/yr
Parallax (π)	12.5320 ± 0.1008 mas[1]
Distance	260 ± 2 ly (79.8 ± 0.6 pc)
Absolute magnitude (MV)	+0.54[3]
Details
Mass	1.72[2] M☉
Radius	11.42[1] R☉
Luminosity	67.6[2] L☉
Surface gravity (log g)	3.01[4] cgs
Temperature	4,763±26[2] K
Metallicity [Fe/H]	−0.20[4] dex
Rotational velocity (v sin i)	2.9[5] km/s
Age	2.63[2] Gyr
Other designations
4 Vul, BD+19°4010, Gaia DR2 4515855716012824704, HD 182762, HIP 95498, HR 7385, SAO 104818, WDS J19255+1948A[6]
Database references
SIMBAD	data

At the age of about 2.6 billion years old,^[2] this is an aging giant star with a stellar classification of K0 III,^[2] having exhausted the supply of hydrogen at its core and evolved off the main sequence. It is now a red clump giant, indicating that it is on the horizontal branch and is generating energy through the fusion of helium at its core.^[10] The star has an estimated 1.72^[2] times the mass of the Sun and has expanded to 11.42^[1] times the Sun's radius. It is radiating 67.6^[2] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,763 K.^[2]

References

1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
2. Luck, R. Earle (2015), "Abundances in the Local Region. I. G and K Giants", Astronomical Journal, 150 (3), 88, arXiv:1507.01466, Bibcode:2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88, S2CID 118505114.
3. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
4. Soubiran, C.; et al. (June 2010), "The PASTEL catalogue of stellar parameters", Astronomy and Astrophysics, 515: A111, arXiv:1004.1069, Bibcode:2010A&A...515A.111S, doi:10.1051/0004-6361/201014247, S2CID 118362423.
5. Massarotti, Alessandro; et al. (2008), "Rotational and Radial Velocities for a Sample of 761 Hipparcos giants and the role of binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209.
6. "4 Vul". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-04-05.
7. 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.
8. Kaler, James B., "The Coathanger, A Non-Cluster", Stars, University of Illinois, retrieved 2018-04-07.
9. Baumgardt, H. (December 1998), "The nature of some doubtful open clusters as revealed by HIPPARCOS", Astronomy and Astrophysics, 340: 402−414, Bibcode:1998A&A...340..402B.
10. Alves, David R. (August 2000), "K-Band Calibration of the Red Clump Luminosity", The Astrophysical Journal, 539 (2): 732–741, arXiv:astro-ph/0003329, Bibcode:2000ApJ...539..732A, doi:10.1086/309278, S2CID 16673121.