| 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] |
| Astrometry | |
| HK Tauri A | |
| Proper motion (μ) | RA: 5.076[2]mas/yr Dec.: −22.944[2]mas/yr |
| Parallax (π) | 7.6247±0.0317 mas[2] |
| Distance | 428 ± 2 ly (131.2 ± 0.5 pc) |
| HK Tauri B | |
| Proper motion (μ) | RA: 2.668[3] mas/yr Dec.: −20.457[3] mas/yr |
| Parallax (π) | 7.780 ± 0.6322 mas[3] |
| Distance | 420 ± 30 ly (130 ± 10 pc) |
| Position (relative to HK Tauri A)[4] | |
| Component | HK Tauri B |
| Angular distance | 2.32″ |
| Position angle | 170.4° |
| Projected separation | 309AU |
| 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 youngbinary star system in the constellation ofTaurus about 434light-years away, belonging to theTaurus Molecular Cloud.
The two stars of the HK Tauri system are separated by2.32″, equivalent to309 AU at the distance of HK Tauri. The primary is apre-main sequence star with a mass of 0.44 M☉, while the secondary has a mass of 0.37 M☉.[4]
Both members of the binary are medium-mass objects still contracting towards themain 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]
The companion star HK Tauri B is surrounded by aprotoplanetary disk visible nearly edge-on. It contains water and carbon dioxide ices, along with gaseouscarbon 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]
| Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| protoplanetary disk | 0–28.7AU | 56.9±0.5° | — | |||
| Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| protoplanetary disk | 0–68.0AU | 83.2±0.2° | — | |||
