T Chamaeleontis

T Chamaeleontis (T Cha), also known as HIP 58285, is a T Tauri star located in the southern circumpolar constellation Chamaeleon. It has an apparent magnitude that ranges from 10.05 to 14.50,^[3] which is below the limit for naked eye visibility. Gaia DR3 parallax measurements place the object 335 light years away^[2] and it is currently receding with a heliocentric radial velocity of 13.8 km/s.^[9] At its current distance, T Cha's average brightness is diminished by 0.31 magnitudes due to extinction from interstellar dust. It has an average absolute magnitude of +6.55.^[10]

T Chamaeleontis

A visual band light curve for T Chamaeleontis, plotted from AAVSO data[1]
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Chamaeleon
Right ascension	11h 57m 13.52451s[2]
Declination	−79° 21′ 31.5305″[2]
Apparent magnitude (V)	10.05 - 14.50[3]
Characteristics
Evolutionary stage	T Tauri star[4]
Spectral type	K0e[5]
U−B color index	+0.63[6]
B−V color index	+1.14[6]
J−K color index	+1.67[7]
Variable type	Orion variable[8]
Astrometry
Radial velocity (Rv)	13.8±0.1[9] km/s
Proper motion (μ)	RA: −41.586 mas/yr[2] Dec.: −8.655 mas/yr[2]
Parallax (π)	9.7356±0.0332 mas[2]
Distance	335 ± 1 ly (102.7 ± 0.4 pc)
Absolute magnitude (MV)	+6.55[10]
Details
Mass	0.65[11] M☉
Radius	0.65±0.09[12] R☉
Luminosity	0.29[13] L☉
Surface gravity (log g)	4.50[13] cgs
Temperature	5,111[14] K
Metallicity [Fe/H]	+0.09±0.15[15] dex
Rotational velocity (v sin i)	39±3[16] km/s
Age	12.7[17] Myr
Other designations
T Cha, HIP 58285, TYC 9419-1187-1, GSC 09419-01187, 2MASS J11571348-7921313
Database references
SIMBAD	data

History

The object was first suspected to be a RW Aurigae-type star in 1949.^[18] It was categorized as a T-Tauri star in 1975. In the same year, it was suspected to be variable and the variability was confirmed in 1976.^[19] A 1993 paper said that it might be a weak-lined YY Orionis star.^[20] T Cha might be either a member of the young ε Chamaeleontis association or the slightly older η Chamaeleontis association.^[17][9] T Cha is an Orion variable that fluctuates between 10.05 and 14.5.^[3][8]

Physical characteristics

T Cha has a stellar classification of K0e,^[5] indicating that it is a K-type star with emission lines in its spectrum. It is currently on the T Tauri stage,^[4] accreting matter at a rate of 3.16×10⁻⁹ to 1.26×10⁻⁸ M_☉/yr.^[21] It has 65% the mass of the Sun^[11] but the radius is highly uncertain. Estimates range from 0.65 to 4.36 times the radius of the Sun.^[22][12] It radiates 29% the luminosity of the Sun^[13] from its photosphere at an effective temperature of 5,111 K,^[14] giving it an orange hue. T Cha has a poorly constrained metallicity of [Fe/H] = +0.09^[15] and it spins modestly with a projected rotational velocity of 39 km/s.^[16]