HR 273

HR 273
Location of HR 273 (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Cassiopeia
Right ascension 00h 58m 31.06245s[1]
Declination +66° 21′ 06.4522″[1]
Apparent magnitude (V) 5.97[2]
Characteristics
Spectral type A0 III[3]
U−B color index −0.13[2]
B−V color index −0.02[2]
Astrometry
Radial velocity (Rv)−10.3[4] km/s
Proper motion (μ) RA: +43.81[1] mas/yr
Dec.: −13.62[1] mas/yr
Parallax (π)9.31 ± 0.33 mas[1]
Distance350 ± 10 ly
(107 ± 4 pc)
Absolute magnitude (MV)0.3[5]
Orbit[6]
Period (P)6.82054 days
Eccentricity (e)0
Inclination (i)20.5°
Semi-amplitude (K1)
(primary)		24.60 km/s
Semi-amplitude (K2)
(secondary)		38.43 km/s
Details
A
Mass2.5[6] M☉
Surface gravity (log g)4.0[7] cgs
Temperature11,400[7] K
B
Surface gravity (log g)4.5[7] cgs
Temperature7,800[7] K
Rotational velocity (v sin i)3.2+0.3
−1.9[7] km/s
Other designations
HR 273, HD 5550, HIP 4572, BD+65°115
Database references
SIMBADdata

HR 273 is a chemically peculiar spectroscopic binary system in the northern circumpolar constellation of Cassiopeia. It has an apparent visual magnitude of 5.9 making it faintly visible to the naked eye from dark suburban skies. Parallax measurements with the Hipparcos spacecraft put this system at a distance of roughly 350 light years.[1]

The primary, HR 273 A, is an Ap star[8] and the secondary is an Am star, making this a very unusual binary system. The primary has a magnetic field of 65 gauss, amongst the weakest seen in any Ap star. The magnetic field in the secondary is too weak to detect.[7]

Component A has a spectral type of A0 III, and has unusually strong lines of strontium, chromium, and europium so it is known as a SrCrEu star.[6] Although some spectral lines of the secondary star can be clearly distinguished, its spectral type cannot be clearly assigned. It is thought to be a late class A star, cooler than the primary. The primary star has been rotationally braked so that its rotational period closely matches its orbital period.[7]

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  6. ^ a b c Cite error: The named reference carrier was invoked but never defined (see the help page).
  7. ^ a b c d e f g Cite error: The named reference alecian was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference renson was invoked but never defined (see the help page).