Upsilon Lupi

Upsilon Lupi, Latinized from υ Lupi, is a star system in the southern constellation of Lupus. It is faintly visible to the naked eye with an apparent visual magnitude of 5.37.^[2] Based upon an annual parallax shift of 8.02^[1] mas as seen from Earth, it is located around 410 light years from the Sun. The two components of Upsilon Lupi share a common proper motion through space and most likely form a wide binary star system.^[10] As of 1945, the pair had an angular separation of 1.50 arc seconds along a position angle of 40°.^[3]

Upsilon Lupi

The location of Upsilon Lupi (υ) in the constellation of Lupus (shown as a red target's bullseye).
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Lupus
Right ascension	15h 24m 45.00855s[1]
Declination	−39° 42′ 36.9524″[1]
Apparent magnitude (V)	5.37[2] (5.37 + 10.90)[3]
Characteristics
Spectral type	A0p Si[4]
B−V color index	−0.11[2]
Astrometry
Radial velocity (Rv)	−7.6±2.8[5] km/s
Proper motion (μ)	RA: −26.10[1] mas/yr Dec.: −54.77[1] mas/yr
Parallax (π)	8.02±0.62 mas[1]
Distance	410 ± 30 ly (125 ± 10 pc)
Absolute magnitude (MV)	−0.10[6]
Details
υ Lup A
Luminosity	113[7] L☉
Temperature	10,049[7] K
Rotational velocity (v sin i)	0[8] km/s
Other designations
υ Lup, CD−39°9827, HD 136933, HIP 75439, HR 5719, SAO 206597[9]
Database references
SIMBAD	data

The brighter member, component A, is a chemically peculiar Ap star with a stellar classification of A0p Si,^[4] where the 'Si' suffix indicates an abnormal abundance of silicon in the star's photosphere. A magnetic field has been detected with a quadratic field strength of (764.7±311.3)×10⁻⁴ T.^[11] The star is radiating 113 times the solar luminosity from its outer atmosphere at an effective temperature of 10,049 K.^[7]

The magnitude 10.9 companion star, component B, has a visual magnitude of 10.90.^[3] It may be the source of the X-ray emission detected coming from these coordinates.^[12]