HAT-P-18

Last updated
HAT-P-18
Observation data
Epoch J2000       Equinox J2000
Constellation Hercules
Right ascension 17h 05m 23.1476s [1]
Declination +33° 00′ 44.9391″ [1]
Apparent magnitude  (V)12.759 [2]
Characteristics
Spectral type K2V
Astrometry
Radial velocity (Rv)-11.83 km/s
Proper motion (μ)RA: -14.073  mas/yr
Dec.: -36.689  mas/yr
Parallax (π)6.1669 ± 0.0231  mas [1]
Distance 529 ± 2  ly
(162.2 ± 0.6  pc)
Details [3]
Mass 0.750+0.015
−0.014  M☉
Radius 0.7202+0.0095
−0.01  R☉
Luminosity 0.27±0.04 [4]   L☉
Surface gravity (log g)4.599±0.013  cgs
Temperature 4835+39
−35  K
Metallicity 0.044+0.060
−0.051
Rotation 14.66±0.03 d [4]
Rotational velocity (v sin i)0.5±0.5 [4]  km/s
Age 12.4+4.4
−6.4 [4]   Gyr
Other designations
Gaia DR2  1334573817793362560, GSC  02594-00646, 2MASS J17052315+3300450 [1]
Database references
SIMBAD data

HAT-P-18 is a K-type main-sequence star about 530 light-years away. The star is very old and has a concentration of heavy elements similar to solar abundance. [4] A survey in 2015 detected very strong starspot activity on HAT-P-18. [5]

Planetary system

In 2010 a transiting hot Saturn-sized planet was detected. [2] Its equilibrium temperature is 841 K. [6]

In 2014, observations utilizing the Rossiter–McLaughlin effect detected an exoplanet, HAT-P-18b, on a retrograde orbit, with an angle between orbital plane of the planet and the parent star equatorial plane equal to 132±15°. [7]

Transit-timing variation measurements in 2015 did not detect additional planets in the system. [8]

In 2016, the transmission optical spectra of the planet indicated that the atmosphere is lacking detectable clouds or hazes, and is blue in color due to Rayleigh scattering of light. [9] The atmosphere seems to gradually evaporate, but at a slow rate - less than 2% of planetary mass is lost per one billion years. [10] By contrast, spectra taken in 2022 has showed an extensive hazes and clear evidence of water vapour, along with the tail of escaping helium. [11]

The dayside temperature of HAT-P-18b was measured in 2019 to be 1004+78
−94 K. [12]

Size comparison of HAT-P-18 b and Jupiter Exoplanet Comparison HAT-P-18 b.png
Size comparison of HAT-P-18 b and Jupiter
The HAT-P-18 planetary system [2]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b0.183+0.034
−0.032  MJ 		0.04649±5.508029±0.00000420.106+0.15
−0.084		88.79±0.21° 0.947±0.044  RJ

Related Research Articles

The Hungarian Automated Telescope Network (HATNet) project is a network of six small fully automated "HAT" telescopes. The scientific goal of the project is to detect and characterize extrasolar planets using the transit method. This network is used also to find and follow bright variable stars. The network is maintained by the Center for Astrophysics | Harvard & Smithsonian.

WASP-11/HAT-P-10 is a binary star. It is a primary main-sequence orange dwarf star. Secondary is M-dwarf with a projected separation of 42 AU. The system is located about 424 light-years away in the constellation Aries.

HAT-P-8 is a magnitude 10 star located 700 light-years away in Pegasus. It is a F-type star about 28% more massive than the Sun. Two red dwarf companions have been detected around HAT-P-8. The first has a spectral type of M5V and has a mass of 0.22 M☉. The second is even less massive, at 0.18 M☉, and its spectral type is M6V.

<span class="mw-page-title-main">HAT-P-27</span> Star in the constellation Virgo

HAT-P-27, also known as WASP-40, is the primary of a binary star system about 650 light-years away. It is a G-type main-sequence star. The star's age is similar to the Sun's at 4.4 billion years. HAT-P-27 is enriched in heavy elements, having a 195% concentration of iron compared to the Sun.

<span class="mw-page-title-main">GJ 3470 b</span> Hot Neptune orbiting GJ 3470

GJ 3470 b is an exoplanet orbiting the star GJ 3470, located in the constellation Cancer. With a mass of just under 14 Earth-masses and a radius approximately 4.3 times that of Earth's, it is likely something akin to Neptune despite the initially strong belief that the planet was not covered in clouds like the gas giants in the Solar System.

HAT-P-26 is a K-type main-sequence star about 466 light-years away. A survey in 2015 did not find any stellar companions in orbit around it, although a red dwarf companion with a temperature 4000+100
−350 K is suspected on wide orbit.

HAT-P-23 is a G-type main-sequence star about 1200 light-years away. It has a rapid rotation for its advanced age of 4 billion years, and exhibits a strong starspot activity. The star may be in the process of being spun up by the giant planet on close orbit. The star is enriched in heavy elements, having about 140% amount of metals compared to solar abundance.

HAT-P-19 is a K-type main-sequence star about 650 light-years away. The star is old yet metal enriched, having amount of heavy elements 250% of solar abundance. The survey in 2012 have failed to find any stellar companions to HAT-P-19.

HAT-P-16 is a F-type main-sequence star about 740 light-years away. The star has a concentration of heavy elements slightly higher than solar abundance, and low starspot activity. The survey in 2015 have failed to find any stellar companions to it. The spectral analysis in 2014 have discovered the HAT-P-16 has a carbon to oxygen molar ratio of 0.58±0.08, close to Sun`s value of 0.55.

HAT-P-15 is a G-type main-sequence star about 630 light-years away. The star is older than Sun yet has a concentration of heavy elements roughly 190% of solar abundance. The star has no noticeable starspot activity.

HAT-P-29, also known as Muspelheim since 2019, is a star about 1,040 light-years away. It is a G-type main-sequence star. The star's age of 2.2±1.0 billion years is less than half that of the Sun. HAT-P-29 is slightly enriched in heavy elements, having 35% more iron than the Sun.

HAT-P-28 is the primary of a binary star system about 1320 light-years away. It is a G-type main-sequence star. The star's age is older than the Sun's at 6.1+2.6
−1.9 billion years. HAT-P-28 is slightly enriched in heavy elements, having a 130% concentration of iron compared to the Sun. Since 2014, the binary star system is suspected to be surrounded by a debris disk with a 6.1″(2500 AU) radius.

HAT-P-41 is a binary star system. Its primary is a F-type main-sequence star. Its surface temperature is 6390±100 K. compared to the Sun, HAT-P-41 is enriched in heavy elements, with a metallicity Fe/H index of 0.21±0.10, but is much younger at an age of 2.2±0.4 billion years.

References

  1. 1 2 3 4 HAT-P-18 -- Star
  2. 1 2 3 Hartman, J. D.; Bakos, G. Á.; Sato, B.; Torres, G.; Noyes, R. W.; Latham, D. W.; Kovács, G.; Fischer, D. A.; Howard, A. W.; Johnson, J. A.; Marcy, G. W.; Buchhave, L. A.; Füresz, G.; Perumpilly, G.; Béky, B.; Stefanik, R. P.; Sasselov, D. D.; Esquerdo, G. A.; Everett, M.; Csubry, Z.; Lázár, J.; Papp, I.; Sári, P. (2010), "HAT-P-18b and HAT-P-19b: Two Low-Density Saturn-Mass Planets Transiting Metal-Rich K Stars", The Astrophysical Journal, 726: 52, arXiv: 1007.4850 , doi:10.1088/0004-637X/726/1/52, S2CID   10896305
  3. ↑ Wang, Xian-Yu; et al. (1 July 2021). "Transiting Exoplanet Monitoring Project (TEMP). VI. The Homogeneous Refinement of System Parameters for 39 Transiting Hot Jupiters with 127 New Light Curves". The Astrophysical Journal Supplement Series. 255 (1). 15. arXiv: 2105.14851 . Bibcode:2021ApJS..255...15W. doi:10.3847/1538-4365/ac0835. S2CID   235253975.
  4. 1 2 3 4 5 Everett, Mark E.; Howell, Steve B.; Silva, David R.; Szkody, Paula (2013), "Spectroscopy of Faint Kepler Mission Exoplanet Candidate Host Stars", The Astrophysical Journal, 771 (2): 107, arXiv: 1305.0578 , Bibcode:2013ApJ...771..107E, doi:10.1088/0004-637X/771/2/107, S2CID   119270620
  5. ↑ Piskorz, Danielle; Knutson, Heather A.; Ngo, Henry; Muirhead, Philip S.; Batygin, Konstantin; Crepp, Justin R.; Hinkley, Sasha; Morton, Timothy D. (2015), "Friends of Hot Jupiters. III. An Infrared Spectroscopic Search for Low-Mass Stellar Companions", The Astrophysical Journal, 814 (2): 148, arXiv: 1510.08062 , Bibcode:2015ApJ...814..148P, doi:10.1088/0004-637X/814/2/148, S2CID   11525988
  6. ↑ Planet HAT-P-18 b at exoplanets.eu
  7. ↑ Esposito, M.; Covino, E.; Mancini, L.; Harutyunyan, A.; Southworth, J.; Biazzo, K.; Gandolfi, D.; Lanza, A. F.; Barbieri, M.; Bonomo, A. S.; Borsa, F.; Claudi, R.; Cosentino, R.; Desidera, S.; Gratton, R.; Pagano, I.; Sozzetti, A.; Boccato, C.; Maggio, A.; Micela, G.; Molinari, E.; Nascimbeni, V.; Piotto, G.; Poretti, E.; Smareglia, R. (2014), "The GAPS Programme with HARPS-N at TNG. III: The retrograde orbit of HAT-P-18b", Astronomy and Astrophysics, 564, arXiv: 1403.6728 , Bibcode:2014A&A...564L..13E, doi:10.1051/0004-6361/201423735, S2CID   59939759
  8. ↑ Seeliger, M.; Kitze, M.; Errmann, R.; Richter, S.; Ohlert, J. M.; Chen, W. P.; Guo, J. K.; Göğüş, E.; Güver, T.; Aydın, B.; Mottola, S.; Hellmich, S.; Fernandez, M.; Aceituno, F. J.; Dimitrov, D.; Kjurkchieva, D.; Jensen, E.; Cohen, D.; Kundra, E.; Pribulla, T.; Vaňko, M.; Budaj, J.; Mallonn, M.; Wu, Z.-Y.; Zhou, X.; Raetz, St.; Adam, C.; Schmidt, T. O. B.; Ide, A.; et al. (2015), "Ground-based transit observations of the HAT-P-18, HAT-P-19, HAT-P-27/WASP40 and WASP-21 systems", Monthly Notices of the Royal Astronomical Society, 451 (4): 4060–4072, arXiv: 1508.06215 , doi:10.1093/mnras/stv1187, S2CID   56034663
  9. ↑ Kirk, J.; Wheatley, P. J.; Louden, T.; Doyle, A. P.; Skillen, I.; McCormac, J.; Irwin, P. G. J.; Karjalainen, R. (2016), "Rayleigh scattering in the transmission spectrum of HAT-P-18b", Monthly Notices of the Royal Astronomical Society, 468 (4): 3907–3916, arXiv: 1611.06916 , doi:10.1093/mnras/stx752, S2CID   1058289
  10. ↑ Paragas, Kimberly; Vissapragada, Shreyas; Knutson, Heather A.; Oklopčić, Antonija; Chachan, Yayaati; Greklek-Mckeon, Michael; Dai, Fei; Tinyanont, Samaporn; Vasisht, Gautam (2021), "Metastable Helium Reveals an Extended Atmosphere for the Gas Giant HAT-P-18b", The Astrophysical Journal Letters, 909 (1): L10, arXiv: 2102.08392 , Bibcode:2021ApJ...909L..10P, doi:10.3847/2041-8213/abe706, S2CID   231942657
  11. ↑ Fu, Guangwei; Espinoza, Néstor; Sing, David K.; Lothringer, Joshua D.; Dos Santos, Leonardo A.; Rustamkulov, Zafar; Deming, Drake; Kempton, Eliza M.-R.; Komacek, Thaddeus D.; Knutson, Heather A.; Albert, Loïc; Pontoppidan, Klaus; Volk, Kevin; Filippazzo, Joseph (2022), "Water and an Escaping Helium Tail Detected in the Hazy and Methane-depleted Atmosphere of HAT-P-18b from JWST NIRISS/SOSS", The Astrophysical Journal Letters, 940 (2): L35, arXiv: 2211.13761 , Bibcode:2022ApJ...940L..35F, doi:10.3847/2041-8213/ac9977, S2CID   254017890
  12. ↑ Wallack, Nicole L.; Knutson, Heather A.; Morley, Caroline V.; Moses, Julianne I.; Thomas, Nancy H.; Thorngren, Daniel P.; Deming, Drake; Désert, Jean-Michel; Fortney, Jonathan J.; Kammer, Joshua A. (2019), "Investigating Trends in Atmospheric Compositions of Cool Gas Giant Planets UsingSpitzer Secondary Eclipses", The Astronomical Journal, 158 (6): 217, arXiv: 1908.00014 , Bibcode:2019AJ....158..217W, doi:10.3847/1538-3881/ab2a05, S2CID   199064423


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