V2052 Ophiuchi

V2052 Ophiuchi, also known as HR 6684, is a star about 920 light years from Earth in the constellation Ophiuchus.^[2] It is a 5th-magnitude star, making it faintly visible to the naked eye of an observer far from city lights. V2052 Ophiuchi is a Beta Cephei variable (β Cep) star, varying slightly in brightness from magnitude 5.81 to 5.84 over a period of about 3.4 hours.^[3]

V2052 Ophiuchi

A light curve for V2052 Ophiuchi, plotted from Hipparcos data[1]
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Ophiuchus
Right ascension	17h 56m 18.40012s[2]
Declination	+00° 40′ 13.2733″[2]
Apparent magnitude (V)	5.81 – 5.84[3]
Characteristics
Spectral type	B2 IV–V[4]
U−B color index	−0.66[5]
B−V color index	+0.09[5]
Variable type	β Cephei[3]
Astrometry
Proper motion (μ)	RA: −4.997±0.038[2] mas/yr Dec.: −0.369±0.038[2] mas/yr
Parallax (π)	3.5446±0.0453 mas[2]
Distance	920 ± 10 ly (282 ± 4 pc)
Absolute magnitude (MV)	−2.54[6]
Details
Mass	8.9±0.7[7] M☉
Radius	4.1±0.2[8] R☉
Luminosity	3,426[2] L☉
Surface gravity (log g)	4.00[4] cgs
Temperature	23,000±1,000[4] K
Metallicity [Fe/H]	+0.012[2] dex
Rotation	3.638833±0.000003 d[9]
Rotational velocity (v sin i)	60[9] km/s
Age	21[10] Myr
Other designations
HR 6684, HD 163472, HIP 87812, SAO 122935[11]
Database references
SIMBAD	data

In 1972, Mikolaj Jerzykiewicz announced that HR 6684 is a variable star, based on his observations using the 0.6 meter Air Force Telescope on Mauna Kea. He classified the star as a β Cep variable with period of 0.13989 days, He further noted that if confirmed, it would be the least luminous and shortest period β Cep star known up to that date.^[12] Spectroscopic and photometric observations by D. Harold McNamara and Bruce Bills in 1973 confirmed Jerzykiewicz's results.^[13] In 1973, HR 6684 was given the variable star designation V2052 Ophiuchi.^[14]

In 1994, Henryk Cugier et al. determined that V2052 Ophiuchi pulsated primarily in the fundamental (l=0) radial mode.^[15] A much less powerful non-radial pulsation mode was identified in 2003.^[8] Ultraviolet observations by the TD-1A satellite show that throughout its pulsation cycle, the temperature of V2052 Ophiuchi varies by 1040±880 K, and its radius changes by 3.1%±0.9%.^[5] Observations at the Pic du Midi Observatory showed that V2052 Ophiuchi has a dipole magnetic field, the axis of which is offset from the star's center, and there are helium spots on the surface near the magnetic poles.^[9] V2052 Ophiuchi is a type of chemically peculiar star known as a helium-strong star. Its surface is over-abundant in helium, and under-abundant in oxygen, perhaps due to its magnetic field differentially effecting the diffusion of elements in its atmosphere.^[8]