GI Tauri and GK Tauri

GI Tauri and GK Tauri

A visual band light curve for GK tauri, adapted from Bouvier et al. (1993)[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Taurus
GK Tauri
Right ascension	04^h 33^m 34.5627^s[2]
Declination	+24° 21′ 05.8545″[2]
Apparent magnitude (V)	15.10
GI Tauri
Right ascension	04^h 33^m 34.0609^s[3]
Declination	+24° 21′ 17.0674″[3]
Characteristics
GK Tauri
Evolutionary stage	pre-main-sequence star
Spectral type	K7[4]
Apparent magnitude (G)	11.990[2]
Variable type	T Tau
GI Tauri
Apparent magnitude (G)	12.608[3]
Astrometry
GK Tauri
Proper motion (μ)	RA: 7.46±0.02 mas/yr[2] Dec.: −20.510±0.017 mas/yr[2]
Parallax (π)	7.7433 ± 0.0185 mas[2]
Distance	421 ± 1 ly (129.1 ± 0.3 pc)
GI Tauri
Proper motion (μ)	RA: 5.76±0.02 mas/yr[3] Dec.: −20.642±0.019 mas/yr[3]
Parallax (π)	7.7258 ± 0.0198 mas[3]
Distance	422 ± 1 ly (129.4 ± 0.3 pc)
Position (relative to GK Tauri)[5]
Component	GI Tauri
Angular distance	13.15797±0.00005″
Position angle	328.4399±0.0002°
Projected separation	1700 AU
Details[5]
GK Tauri
Mass	0.79±0.07 M☉
Luminosity	0.80[6] L☉
Temperature	4007[6] K
Age	2±1 Myr
GI Tauri
Mass	0.53^+0.09 −0.11 M☉
Luminosity	0.49[6] L☉
Temperature	3792[6] K
Age	2±1 Myr
Other designations
GK Tauri: Gaia EDR3 147790206908395776, 2MASS J04333456+2421058, GSC 01829-00040
GI Tauri: Gaia EDR3 147790000749072768, 2MASS J04333405+2421170, GSC 01829-00082
Database references
SIMBAD	data

GK Tauri is a young T Tauri-type pre-main sequence star in the constellation of Taurus about 421 light years away, belonging to the Taurus Molecular Cloud.

System

The stars GK Tauri and GI Tauri form a wide binary system, with the projected separation between components being 1700 AU. The secondary component's orbit is not very eccentric, with a periastron of at least 890 AU.[5]

GK Tauri was originally believed to have a close stellar companion WDS J04336+2421Ab.[7] However, it was found to be an unrelated background star according to Gaia data.[8]

Properties

Both members of the binary system are medium-mass objects still contracting towards the main sequence and accreting mass, with the primary GK Tauri being close to entering the main sequence.[4][5]

Protoplanetary system

Both stars are surrounded by compact protoplanetary disks, although the reason for the small disk sizes is not clear.[5] GK Tauri's spectrum indicates a possible gap in the protoplanetary disk and a planet orbiting within the gap, with a semimajor axis of 2.4^+1.5
_−1.0 AU.[4]

The GK Tauri planetary system[5]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
protoplanetary disk	0–19 AU				40.2^+5.9 −6.2°	—

The GI Tauri planetary system[5]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
protoplanetary disk	0–25 AU				43.8±1.1°	—

References

1. Bouvier, J.; Cabrit, S.; Fernandez, M.; Martin, E. L.; Matthews, J. M. (May 1993). "COYOTES I : the photometric variability and rotational evolution of T Tauri stars". Astronomy and Astrophysics. 272: 176–206. Bibcode:1993A&A...272..176B. Retrieved 31 March 2022.
2. Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
3. Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
4. Marsh, Kenneth A.; Mahoney, Michael J. (1993), "Do the Spectral Energy Distributions of GK Tauri and HK Tauri Indicate the Presence of Planetary Companions?", The Astrophysical Journal, 405: L71, Bibcode:1993ApJ...405L..71M, doi:10.1086/186768
5. Pearce, Logan A.; Kraus, Adam L.; Dupuy, Trent J.; Mann, Andrew W.; Newton, Elisabeth R.; Tofflemire, Benjamin M.; Vanderburg, Andrew (2020), "Orbital Parameter Determination for Wide Stellar Binary Systems in the Age of Gaia", The Astrophysical Journal, 894 (2): 115, arXiv:2003.11106, Bibcode:2020ApJ...894..115P, doi:10.3847/1538-4357/ab8389, S2CID 215547945
6. Braun, Teresa A. M.; Yen, Hsi-Wei; Koch, Patrick M.; Manara, Carlo F.; Miotello, Anna; Testi, Leonardo (2021), "Dynamical Stellar Masses of Pre-main-sequence Stars in Lupus and Taurus Obtained with ALMA Surveys in Comparison with Stellar Evolutionary Models", The Astrophysical Journal, 908 (1): 46, arXiv:2012.07441, Bibcode:2021ApJ...908...46B, doi:10.3847/1538-4357/abd24f, S2CID 229156020
7. "V* GK Tau". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 18 June 2021.
8. Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.