K2-25

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K2-25
Close-up of K2-25 (noirlab2018l).jpg
K2-25 is the star at the center of this image.
Observation data
Epoch J2000       Equinox J2000
Constellation Taurus [1]
Right ascension 04h 13m 05.6131s [2]
Declination +15° 14′ 52.018″ [2]
Apparent magnitude  (V)15.881 [3]
Characteristics
Spectral type M4.5 V [4]
Apparent magnitude  (J)11.303(21) [5]
Apparent magnitude  (H)10.732(20) [5]
Apparent magnitude  (K)10.444(19) [5]
Variable type Planetary transit [4]
Astrometry
Radial velocity (Rv)38.64(15) [4] km/s
Proper motion (μ)RA: 122.450(38) mas/yr [2]
Dec.: −18.603(26) mas/yr [2]
Parallax (π)22.3572±0.0308  mas [2]
Distance 145.9 ± 0.2  ly
(44.73 ± 0.06  pc)
Details [6]
Mass 0.2634(77)  M☉
Radius 0.2932(93)  R☉
Luminosity 0.00816(29)  L☉
Temperature 3207(58)  K
Metallicity [Fe/H]0.15(3) [4]   dex
Rotation 1.87708(66) d [7]
Rotational velocity (v sin i)7.71(29) [8]  km/s
Age 650(70) [8] [9]   Myr
Other designations
vA 50, HAN 87, Gaia DR3 3311804515502788352, EPIC 210490365, 2MASS J04130560+1514520 [10] [11]
Database references
SIMBAD data
Exoplanet Archive data

K2-25 is a young red dwarf star located in the Hyades cluster. There is a single known Neptune-sized planet in a 3.5 day orbit.

Contents

Hyades cluster

Using proper motion measurements in a search for low-luminosity members of the Hyades cluster, William van Altena first identified the star vA 50 (later known as K2-25) as a probable cluster member. [12] Membership in the Hyades cluster was later confirmed. [13] [14] [4]

Properties

K2-25 is a red dwarf that is only 26% the mass of the Sun and less than 1% of the luminosity. [6] As a member of the Hyades cluster, it is only 650 million years old as compared to the Sun's 4.5 billion. [8]

There is clear evidence for starspot activity in both the Kepler data and radial velocities as well as the associated activity indicators. [15]

Planetary system

The star has one known planet, K2-25b, with searches of the Kepler space telescope data for transits of additional planets being negative. [4] Analysis of transit-timing variations from the Spitzer Space Telescope as well as the MEarth Project also found no evidence of additional planets. [16]

Discovery

Brightness measurements of K2-25 taken by the Kepler space telescope during its extended K2 mission led to the discovery of the transiting planet K2-25b. [4] [10]

Characteristics

K2-25b is a Hot Neptune type planet in an eccentric 3.48 day orbit. [15]

Due to its proximity and the activity levels of its host star, K2-25b should be losing some of its atmosphere to space; however, observations of two transits by the Hubble Space Telescope to search for escaping neutral hydrogen were negative. [17]

The K2-25 planetary system [15]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
K2-25b24.5+5.7
−5.2  M🜨 		0.0287(12)3.48456408+0.0000006
−0.0000005		0.428+0.050
−0.049		88.16+0.18
−0.21 ° 		3.44(12)  R🜨
Location of K2-25 in the Hyades cluster Location of K2-25 (noirlab2018b).jpg
Location of K2-25 in the Hyades cluster

References

  1. ↑ Roman, Nancy G. (1987). "Identification of a Constellation From a Position". Publications of the Astronomical Society of the Pacific. 99 (617): 695–699. Bibcode: 1987PASP...99..695R . doi: 10.1086/132034 . Vizier query form
  2. 1 2 3 4 5 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv: 2208.00211 . Bibcode:2023A&A...674A...1G. doi: 10.1051/0004-6361/202243940 . S2CID   244398875. Gaia DR3 record for this source at VizieR.
  3. ↑ Henden, A. A.; et al. (2016). "VizieR Online Data Catalog: AAVSO Photometric All Sky Survey (APASS) DR9 (Henden+, 2016)". VizieR On-line Data Catalog: II/336. Originally Published in: 2015AAS...22533616H. 2336. Bibcode:2016yCat.2336....0H. Vizier catalog entry
  4. 1 2 3 4 5 6 7 Mann, Andrew W.; et al. (2016). "Zodiacal Exoplanets in Time (ZEIT). I. A Neptune-sized Planet Orbiting an M4.5 Dwarf in the Hyades Star Cluster". The Astrophysical Journal. 818 (1) 46. arXiv: 1512.00483 . Bibcode: 2016ApJ...818...46M . doi: 10.3847/0004-637X/818/1/46 .
  5. 1 2 3 Skrutskie, M. F.; et al. (2006). "The Two Micron All Sky Survey (2MASS)". The Astronomical Journal. 131 (2): 1163–1183. Bibcode: 2006AJ....131.1163S . doi: 10.1086/498708 . Vizier catalog entry
  6. 1 2 Thao, Pa Chia; et al. (2020). "Zodiacal Exoplanets in Time (ZEIT). IX. A Flat Transmission Spectrum and a Highly Eccentric Orbit for the Young Neptune K2-25b as Revealed by Spitzer". The Astronomical Journal. 159 (1) 32. arXiv: 1911.05744 . Bibcode: 2020AJ....159...32T . doi: 10.3847/1538-3881/ab579b . S2CID   208006920.
  7. ↑ Mori, Mayuko; et al. (2024-04-05). "Characterization of starspots on a young M-dwarf K2-25: multi-band observations of stellar photometric variability and planetary transits". Monthly Notices of the Royal Astronomical Society. 530 (1): 167–189. arXiv: 2403.13946 . Bibcode: 2024MNRAS.530..167M . doi: 10.1093/mnras/stae841 .
  8. 1 2 3 Gaidos, E.; et al. (2020). "Zodiacal Exoplanets in Time. XI. The Orbit and Radiation Environment of the Young M Dwarf-Hosted Planet K2-25b". Monthly Notices of the Royal Astronomical Society: Letters. 498 (1). arXiv: 2007.12701 . Bibcode: 2020MNRAS.498L.119G . doi: 10.1093/mnrasl/slaa136 .
  9. ↑ Martín, Eduardo L.; et al. (2018). "The Lithium Depletion Boundary and the Age of the Hyades Cluster". The Astrophysical Journal. 856 (1) 40. arXiv: 1802.07155 . Bibcode: 2018ApJ...856...40M . doi: 10.3847/1538-4357/aaaeb8 .
  10. 1 2 David, Trevor J.; et al. (2016). "New Pleiades Eclipsing Binaries and a Hyades Transiting System Identified by K2". The Astronomical Journal. 151 (5) 112. arXiv: 1602.01901 . Bibcode: 2016AJ....151..112D . doi: 10.3847/0004-6256/151/5/112 .
  11. ↑ "K2-25". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2020-08-17.
  12. ↑ van Altena, W. F. (1966). "Low-luminosity members of the Hyades cluster". The Astronomical Journal. 71: 482–512. Bibcode: 1966AJ.....71..482V . doi:10.1086/109952.
  13. ↑ Röser, S.; et al. (2011). "A deep all-sky census of the Hyades". Astronomy & Astrophysics. 531: A92. arXiv: 1105.6093 . Bibcode: 2011A&A...531A..92R . doi: 10.1051/0004-6361/201116948 . Vizier catalog entry
  14. ↑ Douglas, S. T.; et al. (2014). "The Factory and the Beehive. II. Activity and Rotation in Praesepe and the Hyades". The Astrophysical Journal. 795 (2) 161. arXiv: 1409.7603 . Bibcode: 2014ApJ...795..161D . doi: 10.1088/0004-637X/795/2/161 .
  15. 1 2 3 Stefansson, Gudmundur; et al. (2020-09-30). "The Habitable Zone Planet Finder Reveals a High Mass and Low Obliquity for the Young Neptune K2-25b". The Astronomical Journal. 160 (4) 192. arXiv: 2007.12766 . Bibcode: 2020AJ....160..192S . doi: 10.3847/1538-3881/abb13a .
  16. ↑ Kain, Isabel J.; et al. (2020-03-01). "The Young Planetary System K2-25: Constraints on Companions and Starspots". The Astronomical Journal. 159 (3) 83. arXiv: 1912.05552 . Bibcode: 2020AJ....159...83K . doi: 10.3847/1538-3881/ab655b .
  17. ↑ Rockcliffe, Keighley E.; et al. (2021-09-01). "A Lyα Transit Left Undetected: the Environment and Atmospheric Behavior of K2-25b". The Astronomical Journal. 162 (3) 116. arXiv: 2109.04376 . Bibcode: 2021AJ....162..116R . doi: 10.3847/1538-3881/ac126f .
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