V1298 Tauri

V1298 Tauri

The planetary system V1298 Tauri Credit: Exoplanet Exploration Program and the Jet Propulsion Laboratory for NASA’s Astrophysics Division
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Taurus
Right ascension	04^h 05^m 19.59121^s[1]
Declination	+20° 09′ 25.5635″[1]
Apparent magnitude (V)	10.31 - 10.43[2]
Characteristics
Spectral type	K0-K1.5[3]
Variable type	Irregular[2]
Astrometry
Proper motion (μ)	RA: 5.228 ± 0.131[1] mas/yr Dec.: -16.077 ± 0.048[1] mas/yr
Parallax (π)	9.2139 ± 0.0593 mas[1]
Distance	354 ± 2 ly (108.5 ± 0.7 pc)
Details
Mass	1.095+0.049 −0.047[4] M☉
Radius	1.33+0.04 −0.03[4] R☉
Luminosity	0.934 ± 0.044[3] L☉
Temperature	4970 ± 120[3] K
Rotation	2.97+0.03 −0.04 d[4]
Age	23 ± 4[3] Myr
Other designations
K2-309, 2MASS J04051959+2009256, BD+19 656, EPIC 210818897, RX J0405.3+2009, 1SWASP J040519.59+200925.5
Database references
SIMBAD	data

V1298 Tauri is a young (23±4 Myr) weakly-lined T Tauri star^[5] that is part of the Taurus-Auriga association in the Taurus Molecular Cloud. Alternatively it is part of a proposed moving group, called Group 29 (or 93 Tau group) that is slightly older.^[6][7][3][8] The system has four transiting exoplanets, discovered with the Kepler space telescope in the K2 mission.^[5] One of the planets was discovered in August 2019^[3] and the other three were discovered in November 2019 by the same team.^[5]

Stellar characteristics

A light curve for V1298 Tauri, adapted from David et al. (2019)^[3]

V1298 Tauri has a spectral type of K0 - K1.5 and it has a mass of about 1.1 M_☉. The star appears in x-rays from ROSAT data and it does show strong lithium absorption lines, both signatures of youth and therefore it was a proposed member of Taurus-Auriga. On the other hand it does not show signs of accretion and it lacks infrared excess. Instead it shows H-alpha in absorption.^[3]

The brightness of V1298 Tauri varies in an unpredictable way between a maximum visual magnitude of 10.31 and a minimum of 10.54.^[2] The light curve of the star shows quasi-periodic variability that was interpreted as stellar rotation and starspots. The light curve also showed several flares.^[3]

Based on Gaia DR2 data this star is part of a co-moving pair, together with HD 284154.^[6] The star is included in an analysis of the 93 Tau group, which finds an age of 35 ±5 Myrs.^[8]

Planetary system

V1298 Tauri has four confirmed planets of which planets c, d and b are near a 1:2:3 resonance (with periods of 8.25, 12.40 and 24.14 days). Planet e only shows a single transit in the K2 light curve and has a period larger than 36 days. Planet e might be in a low-order resonance (of 2:3, 3:5, 1:2, or 1:3) with planet b. The system is very young and might be a precursor of a compact multiplanet system. The 2:3 resonance suggests that some close-in planets may either form in resonances or evolve into them on timescales of less than 10 Myr. The planets in the system have a size between Neptune and Saturn. Only planet b has a size similar to Jupiter.^[5]

Models predict that the planets have a minimum core mass of 5 M_E and are surrounded by a thick envelope that make up 20% of their mass. The total mass of planet c and d was predicted to be 2 - 28 M_E and the total mass of planet d and b was predicted to be 9 - 120 M_E.^[5] In a follow-up paper the mass of V1298 Tauri b was constrained to <2.2 M_J.^[9] The planet c was suspected to be shedding mass due to intense irradiation by the host star, but hydrogen tail existence was refuted by 2021.^[10]

Orbits of the planets b and c are nearly coplanar and planet c is not inclined to the equatorial plane of the star, misalignment equals to 2⁺¹²
₋₄ degrees.^[11]

Planet b was observed with Hubble WFC3 and a transmission spectrum was produced. This observation found a clear primordial atmosphere and water vapor absorption. The mass was constrained from this observation to less than 23 earth-masses, making this planet one of the lowest density planet observed. The team retrieved a low metallicity for the atmosphere, challenging formation mechanisms. The planet will likely evolve into a sub-Neptune in the future.^[12] Comparison between the transmission spectrum of planet b and a newly obtained WFC3 transmission spectrum for planet c found that planet b has a large, haze-free envelope. For planet c hazes could not be ruled out. The masses were constrained for planet b to below 20 earth masses and for planet c to 17+13
−6 earth masses. An ongoing transit-timing variation study suggest that both planet b and c are in the mass range of super-Earth to sub-Neptune planets and will evolve into these types of planet.^[13]

Planet e could be a planet with a water-rich core and an substantial hydrogen envelope.^[14] Planet e was possibly detected by Kepler, TESS and CHEOPS in three transits with an orbital period of around 45 days. The transits have different depths, lengths and maybe has TTVs of a few hours. Alternatively CHEOPS could have detected a fifth planet.^[15]

The V 1298 Tauri planetary system^[5]^[9]^[14]^[13]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
c	17+13 −6 M🜨	0.0825 ± 0.0013	8.24958 ± 0.00072	<0.43	88.49+0.92 −0.72°	0.499+0.032 −0.029 RJ
d	<41 M🜨	0.1083 ± 0.0017	12.4032 ± 0.0015	<0.21	89.04+0.65 −0.73°	0.572+0.040 −0.035 RJ
b	<20 M🜨	0.1688 ± 0.0026	24.1396 ± 0.0018	<0.29	89.00+0.46 −0.24°	0.916+0.052 −0.047 RJ
e	0.66 ± 0.26 MJ	0.308+0.182 −0.066	50.29±6.62[16]	<0.57	89.40+0.26 −0.18°	0.89±0.04[16] RJ

See also

• List of nearby stellar associations and moving groups
• List of exoplanets discovered in 2019
• Kepler-223 - the first confirmed system with four exoplanets in resonance
• K2-138 - a system with five exoplanets in a 3:2 resonance chain
• HD 110067 - a system with seven planets in orbital resonance

References

1. Gaia Collaboration (2018-08-01). "Gaia Data Release 2 - Summary of the contents and survey properties". Astronomy & Astrophysics. 616: A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. ISSN 0004-6361. S2CID 49211658.
2. Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1: B/gcvs. Bibcode:2009yCat....102025S.
3. David, Trevor J.; Cody, Ann Marie; Hedges, Christina L.; Mamajek, Eric E.; Hillenbrand, Lynne A.; Ciardi, David R.; Beichman, Charles A.; Petigura, Erik A.; Fulton, Benjamin J.; Isaacson, Howard T.; Howard, Andrew W. (August 2019). "A Warm Jupiter-sized Planet Transiting the Pre-main-sequence Star V1298 Tau". The Astronomical Journal. 158 (2): 79. arXiv:1902.09670. Bibcode:2019AJ....158...79D. doi:10.3847/1538-3881/ab290f. ISSN 0004-6256. S2CID 119003936.
4. Feinstein, Adina D.; David, Trevor J.; Montet, Benjamin T.; Foreman-Mackey, Daniel; Livingston, John H.; Mann, Andrew W. (2022). "V1298 Tau with TESS: Updated Ephemerides, Radii, and Period Constraints from a Second Transit of V1298 Tau E". The Astrophysical Journal Letters. 925 (1): L2. arXiv:2111.08660. Bibcode:2022ApJ...925L...2F. doi:10.3847/2041-8213/ac4745. S2CID 244130016.
5. David, Trevor J.; Petigura, Erik A.; Luger, Rodrigo; Foreman-Mackey, Daniel; Livingston, John H.; Mamajek, Eric E.; Hillenbrand, Lynne A. (2019-10-29). "Four Newborn Planets Transiting the Young Solar Analog V1298 Tau". The Astrophysical Journal. 885 (1): L12. arXiv:1910.04563. Bibcode:2019ApJ...885L..12D. doi:10.3847/2041-8213/ab4c99. ISSN 2041-8213. S2CID 204008446.
6. Oh, Semyeong; Price-Whelan, Adrian M.; Hogg, David W.; Morton, Timothy D.; Spergel, David N. (June 2017). "Comoving Stars in Gaia DR1: An Abundance of Very Wide Separation Comoving Pairs". The Astronomical Journal. 153 (6): 257. arXiv:1612.02440. Bibcode:2017AJ....153..257O. doi:10.3847/1538-3881/aa6ffd. ISSN 0004-6256. S2CID 119351439.
7. Luhman, K. L. (December 2018). "The Stellar Membership of the Taurus Star-forming Region". The Astronomical Journal. 156 (6): 271. arXiv:1811.01359. Bibcode:2018AJ....156..271L. doi:10.3847/1538-3881/aae831. ISSN 0004-6256. S2CID 119471553.
8. Luhman, K. L. (2023-02-01). "A Census of the Taurus Star-forming Region and Neighboring Associations with Gaia". The Astronomical Journal. 165 (2): 37. arXiv:2211.09785. Bibcode:2023AJ....165...37L. doi:10.3847/1538-3881/ac9da3. ISSN 0004-6256.
9. Beichman, Charles; Hirano, Teruyuki; David, Trevor J.; Kotani, Takayuki; Hillenbrand, Lynne A.; Vasisht, Gautam; Ciardi, David R.; Harakawa, Hiroki; Kudo, Tomoyuki; Omiya, Masashi; Kuzuhara, Masayuki (June 2019). "A Mass Limit for the Young Transiting Planet V1298 Tau b". Research Notes of the AAS. 3 (6): 89. Bibcode:2019RNAAS...3...89B. doi:10.3847/2515-5172/ab2c9d. ISSN 2515-5172. S2CID 198445373.
10. Schlawin, Everett; Ilyin, Ilya; Feinstein, Adina D.; Bean, Jacob; Huang, Chenliang; Gao, Peter; Strassmeier, Klaus; Poppenhaeger, Katja (2021), "H-Alpha Variability of V1298 Tau c", Research Notes of the American Astronomical Society, 5 (8): 195, arXiv:2108.08851, Bibcode:2021RNAAS...5..195S, doi:10.3847/2515-5172/ac1f2f, S2CID 237250293
11. Gaidos, E.; Hirano, T.; Beichman, C.; Livingston, J.; Harakawa, H.; Hodapp, K. W.; Ishizuka, M.; Jacobson, S.; Konishi, M.; Kotani, T.; Kudo, T.; Kurokawa, T.; Kuzuhara, M.; Nishikawa, J.; Omiya, M.; Serizawa, T.; Tamura, M.; Ueda, A.; Vievard, S. (2022), "Zodiacal exoplanets in time – XIII. Planet orbits and atmospheres in the V1298 Tau system, a keystone in studies of early planetary evolution", Monthly Notices of the Royal Astronomical Society, 509 (2): 2969–2978, arXiv:2110.10689, doi:10.1093/mnras/stab3107
12. Barat, Saugata; Désert, Jean-Michel; Vazan, Allona; Baeyens, Robin; Line, Michael R.; Fortney, Jonathan J.; David, Trevor J.; Livingston, John H.; Jacobs, Bob; Panwar, Vatsal; Shivkumar, Hinna; Todorov, Kamen O.; Pino, Lorenzo; Mraz, Georgia; Petigura, Erik A. (2024-07-01). "The metal-poor atmosphere of a potential sub-Neptune progenitor". Nature Astronomy. 8 (7): 899–908. arXiv:2312.16924. Bibcode:2024NatAs...8..899B. doi:10.1038/s41550-024-02257-0. ISSN 2397-3366.
13. Barat, Saugata; Désert, Jean-Michel; Goyal, Jayesh M.; Vazan, Allona; Kawashima, Yui; Fortney, Jonathan J.; Bean, Jacob L.; Line, Michael R.; Panwar, Vatsal (2024-07-01), First Comparative Exoplanetology Within a Transiting Multi-planet System: Comparing the atmospheres of V1298 Tau b and c, arXiv:2407.14995, retrieved 2024-10-16
14. Sikora, James; Rowe, Jason; Barat, Saugata; Bean, Jacob L.; Brady, Madison; Désert, Jean-Michel; Feinstein, Adina D.; Gilbert, Emily A.; Henry, Gregory; Kasper, David; Lizotte, Déreck-Alexandre; Matesic, Michael R. B.; Panwar, Vatsal; Seifahrt, Andreas; Shivkumar, Hinna (2023-06-01). "Updated Planetary Mass Constraints of the Young V1298 Tau System Using MAROON-X". The Astronomical Journal. 165 (6): 250. arXiv:2304.00797. Bibcode:2023AJ....165..250S. doi:10.3847/1538-3881/acc865. ISSN 0004-6256.
15. Damasso, M.; Scandariato, G.; Nascimbeni, V.; Nardiello, D.; Mancini, L.; Marino, G.; Bruno, G.; Brandeker, A.; Leto, G.; Marzari, F.; Lanza, A. F.; Benatti, S.; Desidera, S.; Béjar, V. J. S.; Biagini, A. (2023-12-01). "Photometric follow-up of the 20 Myr old multi-planet host star V1298 Tau with CHEOPS and ground-based telescopes". Astronomy and Astrophysics. 680: A8. arXiv:2309.14131. Bibcode:2023A&A...680A...8D. doi:10.1051/0004-6361/202346840. ISSN 0004-6361.
16. Feinstein, Adina D.; David, Trevor J.; Montet, Benjamin T.; Foreman-Mackey, Daniel; Livingston, John H.; Mann, Andrew W. (2022), "V1298 Tau with TESS: Updated Ephemerides, Radii, and Period Constraints from a Second Transit of V1298 Tau E", The Astrophysical Journal Letters, 925 (1): L2, arXiv:2111.08660, Bibcode:2022ApJ...925L...2F, doi:10.3847/2041-8213/ac4745, S2CID 244130016