V509 Cassiopeiae

V509 Cassiopeiae (V509 Cas or HR 8752) is one of two yellow hypergiant stars found in the constellation Cassiopeia, which also contains Rho Cassiopeiae.

V509 Cassiopeiae

The visual band light curve for V509 Cassiopeiae, adapted from Percy and Zsoldos (1992)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cassiopeia
Right ascension 23h 00m 05.1s
Declination +56° 56 43
Apparent magnitude (V) +4.6 - +6.1
Characteristics
Spectral type G0Ia0 (K5Ia0 - A6Ia+)
U−B color index +1.33
B−V color index +1.0 - +1.7
Variable type SRd
Astrometry
Radial velocity (Rv)−50.20 km/s
Proper motion (μ) RA: −2.787 mas/yr
Dec.: −2.054 mas/yr
Parallax (π)0.2078 ± 0.0899 mas
Distance4,810±430 pc
Absolute magnitude (MV)−8.6 (variable)
Details
Mass11 M
Radius390-910 R
Luminosity269,000 (180,000-400,000) L
Temperature4,000-8,000 K
Metallicity [Fe/H]0.0 dex
Other designations
HR 8752, HD 217476, FK5 3839, HIP 113561, SAO 35039, AAVSO 2255+56
Database references
SIMBADdata

HR 8752 is around 15,700 light-years from Earth. It has an apparent magnitude that has varied from below +6 in historical times to a peak of +4.6 and now around +5.3 and is classified as a semiregular variable star of type SRd. It is undergoing strong mass loss as part of its rapid evolution and has recently passed partway through the yellow evolutionary void by ejecting around a solar mass of material in 20 years.

A hot main sequence companion (B1V) was described in 1978 on the basis of a colour excess in the ultraviolet.

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