R Puppis

Not to be confused with Rho Puppis.

R Puppis is a variable star in the constellation Puppis. It is a rare yellow hypergiant and a candidate member of the open cluster NGC 2439. It is also an MK spectral standard for the class G2 0-Ia.^[9]

R Puppis

Location of R Puppis (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Puppis
Right ascension	07h 40m 52.597s[1]
Declination	−31° 39′ 40.20″[1]
Apparent magnitude (V)	6.50 - 6.71[2]
Characteristics
Spectral type	G2 0-Ia[3]
U−B color index	+0.85[4]
B−V color index	+1.18[4]
Variable type	SRd[2]
Astrometry
Radial velocity (Rv)	+68.22[1] km/s
Proper motion (μ)	RA: −2.251[1] mas/yr Dec.: +3.222[1] mas/yr
Parallax (π)	0.2440±0.0180 mas[1]
Distance	13,400 ± 1,000 ly (4,100 ± 300 pc)
Absolute magnitude (MV)	−7.8[5]
Details
Mass	14.3[6] M☉
Radius	477+28 −22[7] R☉
Luminosity	96,600±26,100[7] L☉
Surface gravity (log g)	0.30[8] cgs
Temperature	5,495; (4,100±68 – 6,500)[8] K
Metallicity [Fe/H]	−0.25[8] dex
Other designations
CD−31°4910, GSC 07106-03582, HIP 37415, HR 2974, HD 62058
Database references
SIMBAD	data

NGC 2439, with R Puppis the brightest star

Variability

A visual band light curve for R Puppis, plotted from ASAS data^[10]

R Puppis was identified as a variable star in 1879, and described as having a range of over a magnitude.^[11] Numerous observations over the following 100 years failed to confirm the variations, until the 1970s when clear brightness changes were observed.^[12] These were confirmed by later observations, but with a total visual amplitude of only about 0.2 magnitudes.^[11]

Variable stars such as R Puppis have been described as pseudo-Cepheids, because they lie above the high-luminosity portion of the instability strip and their variations are similar to those of Cepheids although less regular.^[11] R Puppis is formally classified as a semiregular variable of type SRd, meaning F, G, or K giants or supergiants.^[2]