U Antliae

U Antliae (U Ant) is a variable star in the constellation Antlia. It is a carbon star surrounded by two thin shells of dust.

U Antliae

Location of U Antliae (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Antlia
Right ascension	10h 35m 12.852s[1]
Declination	−39° 33′ 45.32″[1]
Apparent magnitude (V)	5.27 - 6.04[2]
Characteristics
Evolutionary stage	AGB
Spectral type	C-N3[3] (C5,3[4])
U−B color index	7.10[5]
B−V color index	2.84[5]
Variable type	LB[6]
Astrometry
Radial velocity (Rv)	41.00[7] km/s
Proper motion (μ)	RA: −31.372±0.228[8] mas/yr Dec.: 2.371±0.267[8] mas/yr
Parallax (π)	3.5717±0.2043 mas[8]
Distance	910 ± 50 ly (280 ± 20 pc)
Absolute magnitude (MV)	−1.87[9]
Details
Radius	422[10][a] R☉
Luminosity	4,500[10] L☉
Temperature	2,300[10] K
Other designations
HR 4153, HD 91793, HIP 51821, CD−38°6579, 2MASS J10351285-3933453, PPM 287864, AAVSO 1030–39, SAO 201533
Database references
SIMBAD	data

ALMA image of the dust shells around U Antliae

U Antliae is an extremely red C-type carbon star. These cool stars on the asymptotic giant branch are further reddened by strong mass loss and dust that forms around the star. U Antliae is calculated to have an effective surface temperature of 2,800 K, although the light that reaches us has an appearance more like that from a black body with a temperature of 2,300 K surrounded by dust at a temperature of 72 K.^[11] It emits most of its radiation in the infrared and although it is only about 500 times brighter than the sun at visual wavelengths,^[9] its bolometric luminosity is 8,000 times higher than the Sun's.^[11]

The visual band light curve of T Antliae, from AAVSO data^[12]

In 1901, Louisa Dennison Wells discovered that the brightness of the star varied, from the examination of photographic plates.^[13] Annie Jump Cannon included the star, with its variable star designation U Antiliae, in her 1907 Second Catalogue of Variable Stars.^[14] U Antliae is an irregular variable star with an apparent magnitude that varies between 5.27 and 6.04. Approximately 900 light years from Earth, it is surrounded by two shells of dust, thought to have been ejected 14,000 and 10,000 years ago.^[15] The exact origin and structure of the shells is uncertain, possibly due to enhanced mass loss during thermal pulses, possibly due to interaction of the stellar wind with interstellar material.^[11]

Notes

1. Applying the Stefan–Boltzmann law with a nominal solar effective temperature of 5,772 K:

   ${\displaystyle {\sqrt {(5772/2,300)^{4}*4,500}}=422.48\ R\odot }$