HK Tauri

Young binary star system in the constellation of Taurus

HK Tauri

A light curve for HK Tauri, adapted from Roggero et al. (2021)[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Taurus
A
Right ascension	04h 31m 50.5716s[2]
Declination	+24° 24′ 17.775″[2]
Apparent magnitude (V)	15.10
B
Right ascension	04h 31m 50.6002s[3]
Declination	+24° 24′ 15.503″[3]
Characteristics
HK Tauri A
Evolutionary stage	pre-main-sequence star
Spectral type	M1.5[4]
Apparent magnitude (G)	14.106[2]
Variable type	T Tau
HK Tauri B
Spectral type	M2[4]
Apparent magnitude (G)	17.962[3]
Distance		420 ± 30 ly (130 ± 10 pc)
Position (relative to HK Tauri A)[4]
Component	HK Tauri B
Projected separation	309 AU
Details
A
Mass	0.44+0.14 −0.11[4] M☉
Luminosity	0.56[5] L☉
Temperature	3680±150[6] K
B
Mass	0.37±0.2[4] M☉
Luminosity	0.42[5] L☉
Temperature	3550±150[6] K
Other designations
2MASS J04315056+2424180, WISE J043150.56+242417.6
HK Tauri A: Gaia EDR3 147847072275324416, Gaia DR2 147847072275324416
HK Tauri B: Gaia EDR3 147847072275766656, Gaia DR2 147847072274696704
Database references
SIMBAD	data

HK Tauri is a young

Taurus Molecular Cloud

.

System

The two stars of the HK Tauri system are separated by 2.32

Both members of the binary are medium-mass objects still contracting towards the main sequence and accreting mass. Their ages are probably young (below 10 million years) but cannot be estimated with any accuracy because both stars are strongly obscured by the protoplanetary disks.^[6]

Protoplanetary system

The companion star HK Tauri B is surrounded by a protoplanetary disk visible nearly edge-on. It contains water and carbon dioxide ices, along with gaseous carbon monoxide.^[7] The disk is unusually flat, with an aspect ratio of 4.4, while most young stars host disks with aspect ratios of about 3.^[8] The disk also contain relatively few large dust particles compared to fine dust, with a size distribution power-law slope of 4.2. The disk mass is relatively small, not larger than 0.0005M_☉, and dust distribution is asymmetric.^[9] The plane of the disk is not aligned with the orbit of the binary.^[10]

Multiple planets embedded in the disk of HK Tauri B have been suspected since 1993,^[11] although none were detected by 2020.^[12]

References