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K2-32

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K2-32
Observation data
Epoch J2000      Equinox J2000
Constellation Ophiuchus[1]
Right ascension 16h 49m 42.2602s[2]
Declination −19° 32′ 34.151″[2]
Apparent magnitude (V) 12.31±0.02[3]
Characteristics
Spectral type G9V[4]
Apparent magnitude (J) 10.404±0.024[5]
Apparent magnitude (H) 9.993±0.025[5]
Apparent magnitude (K) 9.821±0.019[5]
Variable type Planetary transit variable[6]
Astrometry
Radial velocity (Rv)−1.82±0.14[7] km/s
Proper motion (μ) RA: −16.662(18)[2] mas/yr
Dec.: −53.564(13)[2] mas/yr
Parallax (π)6.3939 ± 0.0153 mas[2]
Distance510 ± 1 ly
(156.4 ± 0.4 pc)
Details[3]
Mass0.856±0.028 M☉
Radius0.845+0.044
−0.035 R☉
Surface gravity (log g)4.49±0.05 cgs
Temperature5275±60 K
Metallicity [Fe/H]−0.02±0.04 dex
Rotational velocity (v sin i)0.7 km/s
Age7.9±4.5 Gyr
Other designations
Gaia DR2 4130539180358512768, EPIC 205071984, 2MASS J16494226-1932340[8]
Database references
SIMBADdata

K2-32 is a G9-type main sequence star slightly smaller and less massive than the sun.[4] Four confirmed transiting exoplanets are known to orbit this star.[9] A study of atmospheric escape from the planet K2-32b caused by high-energy stellar irradiation indicates that the star has always been a very slow rotator.[10]

Planetary system

Discovery

The star K2-32 was initially found to have three transiting planet candidates by Andrew Vanderburg and collaborators in 2016.[7] The innermost planet candidate, at that time, K2-32b was confirmed using radial velocity measurements made with the Keck telescope.[4] Confirmation of planets c and d was made by Sinukoff et al. using adaptive optics imaging and computer analysis to eliminate possible false positives.[6]

The Earth-sized planet K2-32e was discovered and validated by René Heller and team in 2019.[9][11]

Transit light curves of all four planets orbiting the star K2-32.[9]

Characteristics

With periods of 4.34, 8.99, 20.66 and 31.71 days the four planets orbits are very close to a 1:2:5:7 orbital resonance chain. The densities of planets b, c, and d are between those of Saturn and Neptune, which suggests large and massive atmospheres. The planet K2-32e with a radius almost identical to that of the Earth is almost certainly a terrestrial planet.[9] All four planets are well inside even the optimistic inner boundary of the habitable zone located at 0.58 astronomical units.[12]

Planetary system of the star K2-32 showing planetary radii and orbital resonances.[9]
The K2-32 planetary system[9][3][13]
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius
K2-32e 2.1+1.3
−1.1 M🜨 		0.04899+0.00041
−0.00038 		4.34934±0.00039 0.043+0.048
−0.030 		89.0±0.7° 1.212+0.052
−0.046 R🜨
K2-32b 15.0+1.8
−1.7 M🜨 		0.07950+0.00066
−0.00062 		8.992±0.00008 0.03+0.032
−0.02 		89.0+0.5
−0.3° 		5.299±0.191 R🜨
K2-32c 8.1±2.4 M🜨 0.13843+0.00115
−0.00108 		20.66093+0.00080
−0.00079 		0.049+0.046
−0.035 		89.4+0.3
−0.2° 		2.134+0.123
−0.102 R🜨
K2-32d 6.7±2.5 M🜨 0.18422+0.00152
−0.00144 		31.71701+0.00101
−0.00096 		0.05+0.053
−0.035 		89.4±0.1° 3.484+0.112
−0.129 R🜨

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. ^ a b c d e 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. ^ a b c Petigura, Erik A.; et al. (2017). "Four Sub-Saturns with Dissimilar Densities: Windows into Planetary Cores and Envelopes". The Astronomical Journal. 153 (4) 142: 142. arXiv:1702.00013. Bibcode:2017AJ....153..142P. doi:10.3847/1538-3881/aa5ea5.
  4. ^ a b c Dai, Fei; et al. (2016). "Doppler Monitoring of Five K2 Transiting Planetary Systems". The Astrophysical Journal. 823 (2) 115: 115. arXiv:1604.01413. Bibcode:2016ApJ...823..115D. doi:10.3847/0004-637X/823/2/115.
  5. ^ a b c Skrutskie, Michael F.; et al. (1 February 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. ^ a b Sinukoff, Evan; et al. (2016). "Eleven Multiplanet Systems From K2 Campaigns 1 and 2 and the Masses of Two Hot Super-Earths". The Astrophysical Journal. 827 (1) 78: 78. arXiv:1511.09213. Bibcode:2016ApJ...827...78S. doi:10.3847/0004-637X/827/1/78.
  7. ^ a b Vanderburg, Andrew; et al. (2016). "Planetary Candidates from the First Year of the K2 Mission". The Astrophysical Journal Supplement Series. 222 (1) 14: 14. arXiv:1511.07820. Bibcode:2016ApJS..222...14V. doi:10.3847/0067-0049/222/1/14.
  8. ^ "K2-32". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-09-01.
  9. ^ a b c d e f Heller, René; Rodenbeck, Kai; Hippke, Michael (2019). "Transit least-squares survey. I. Discovery and validation of an Earth-sized planet in the four-planet system K2-32 near the 1:2:5:7 resonance". Astronomy and Astrophysics. 625 A31: A31. arXiv:1904.00651. Bibcode:2019A&A...625A..31H. doi:10.1051/0004-6361/201935276.
  10. ^ Kubyshkina, D.; et al. (2019). "Close-in Sub-Neptunes Reveal the Past Rotation History of Their Host Stars: Atmospheric Evolution of Planets in the HD 3167 and K2-32 Planetary Systems". The Astrophysical Journal. 879 (1) 26: 26. arXiv:1906.12153. Bibcode:2019ApJ...879...26K. doi:10.3847/1538-4357/ab1e42.
  11. ^ "Astronomers Discover 18 New Small Exoplanets in Kepler Data" (Press release). Sci-News.com. 2019-05-28. Retrieved 2019-09-27.
  12. ^ Wittenmyer, Robert A.; et al. (2018). "The K2-HERMES Survey. I. Planet-candidate Properties from K2 Campaigns 1–3". The Astronomical Journal. 155 (2) 84: 84. arXiv:1712.06774. Bibcode:2018AJ....155...84W. doi:10.3847/1538-3881/aaa3e4.
  13. ^ Lillo-Box, J.; et al. (2020). "Masses for the seven planets in K2-32 and K2-233". Astronomy & Astrophysics. 640 A48: A48. arXiv:2006.01102. Bibcode:2020A&A...640A..48L. doi:10.1051/0004-6361/202037896.
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