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AF Leporis

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AF Leporis
Location of AF Leporis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Lepus
Right ascension 05h 27m 04.76333s[1]
Declination −11° 54′ 03.4660″[1]
Apparent magnitude (V) 6.26 - 6.35[2]
Characteristics
Evolutionary stage Main sequence
Spectral type F8V(n)k:[3]
Apparent magnitude (B) 6.832±0.015[4]
Apparent magnitude (V) 6.295±0.010[4]
Apparent magnitude (G) 6.209±0.003[1]
Apparent magnitude (J) 5.268±0.027[4]
Apparent magnitude (H) 5.087±0.026[4]
Apparent magnitude (K) 4.926±0.021[4]
Variable type RS CVn[2]
Astrometry
Radial velocity (Rv)21.10±0.37[1] km/s
Proper motion (μ) RA: 16.915 mas/yr[1]
Dec.: −49.318 mas/yr[1]
Parallax (π)37.2539 ± 0.0195 mas[1]
Distance87.55 ± 0.05 ly
(26.84 ± 0.01 pc)
Absolute magnitude (MV)4.14[5]
Details
Mass1.09±0.06[6] M☉
Radius1.25±0.06[7] R☉
Luminosity (bolometric)1.84±0.01[8] L☉
Surface gravity (log g)4.30±0.05[6] cgs
Temperature6130±60[7] K
Metallicity [Fe/H]+0.19±0.02[7] dex
Rotation0.9660±0.0023 d[9]
Rotational velocity (v sin i)50±5[7] km/s
Age24±3[7] Myr
Other designations
AF Lep, NSV 16310, BD−12 1169, FK5 2409, HD 35850, HIP 25486, HR 1817, SAO 150461, PPM 215789, TIC 94945758, TYC 5340-1141-1, GCRV 3284, GSC 05340-01141, IRAS 05247-1156[10]
Database references
SIMBADdata

AF Leporis, also known as HD 35850, is a young variable star located 87.5 light-years (26.8 parsecs) away from the Solar System in the constellation of Lepus. With an apparent magnitude of 6.3, it is near the limit of naked eye visibility under ideal conditions. While some studies consider it to be a close spectroscopic binary with a separation of 0.021 AU,[8] other studies show no evidence of binarity, and it is likely that the supposed binarity is an artifact resulting from the presence of starspots.[9][4] AF Leporis is a member of the Beta Pictoris moving group, with an astronomically young age of about 24 million years. It hosts a circumstellar disk and one known exoplanet.[7]

A light curve for AF Leporis, plotted from TESS data[11]

The stellar classification of AF Leporis is F8V(n)k:,[3] matching an F-type main-sequence star that is generating energy through hydrogen fusion at its core. (The 'n' indicates "nebulous" lines due to spin, while the 'k' means it displays interstellar absorption lines. The ':' suffix is used to note some uncertainty in the classification.) AF Leporis is classified as a RS Canum Venaticorum variable star,[2] which means it has an active surface with large star spots that cause the net luminosity to vary as it rotates.

It is about 24 million years old and is spinning rapidly with a projected rotational velocity of around 50 km/s,[7] giving it a rotation period of less than a day.[9] The star has 9%[6] more mass than the Sun and 1.25[7] times the Sun's radius. The abundance of elements with mass greater than hydrogen – the star's metallicity – is higher than in the Sun. AF Leporis is radiating 1.84[8] times the luminosity of the Sun from its photosphere at an effective temperature of 6,130 K.[7]

Planetary system

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Two images of AF Lep b with the SPHERE instrument on the Very Large Telescope[12]

In 2023, a super-Jupiter exoplanet, AF Leporis b, was discovered in orbit around AF Leporis by direct imaging using the NIRC2 instrument at the W. M. Keck Observatory and the SPHERE instrument at the Very Large Telescope. It was also detected in astrometric data from the Hipparcos and Gaia spacecraft, allowing an accurate measurement of its mass.[7][4][13] AF Leporis b was later precovered in imaging data from 2011, allowing a more accurate determination of its orbit.[14]

There have been multiple studies of AF Leporis b, which have found somewhat different parameters. Dynamical mass measurements range from 2.8 MJ[6] to 5.5 MJ.[4] Values for the planet's orbital inclination range from 50°+9°
−12°[7] to ~98°,[13] the former consistent with the stellar inclination of 54°+11°
−9° and suggesting an aligned system.[7] Initial studies found a fairly eccentric orbit for the planet, but the precovery observations show that its orbit is nearly circular.[14]

AF Leporis b has an effective temperature of about 750 K (477 °C; 890 °F), corresponding to an early-T spectral type.[15] Spectroscopic evidence suggests that it has a metal-rich atmosphere with silicate clouds,[6] though further studies are needed to confirm this.[15]

AF Leporis b was observed with JWST NIRCam. The brightness of F444W is relative faint, indicating significant absorption due to carbon monoxide (CO). The strong CO absorption is explained with disequilibrium chemistry and high metallicity. The observations also rule out additional giant planets in the outer region. The study did not find any variability of AF Leporis b.[16] A study with VLT/GRAVITY confirmed many of the previous observations. The GRAVITY instrument did add high precision astrometry, while at the same time providing a K-band spectrum. The new astrometry together with pervious observations was able to constrain the orbit to a circular orbit with an inclination that is aligned with the inclination of the rotation axis of the host star. The K-band spectrum shows prominent methane absorption. The spectrum is also consistent with a metal-rich cloudy atmosphere, with [Fe/H] = 0.75 ±0.25, consistent with the formation via core accretion. The temperature was constrained to 800 ±50 Kelvin. The dynamical mass constrained the planet mass to 3.75 ±0.5 MJ.[17]

The AF Leporis planetary system[17]
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(years) 		Eccentricity Inclination Radius
b 3.75 ±0.5 MJ 8.98+0.15
−0.08 		24.3+0.9
−0.4 		0.013+0.024
−0.010 		57.5+0.6
−0.7° 		1.3 ±0.15 RJ
Debris disk 46±9[18] AU — —

See also

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References

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  1. ^ a b c d e f 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.
  2. ^ a b c 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. ^ a b Gray, R. O.; Corbally, C. J.; et al. (July 2006). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc-The Southern Sample". The Astronomical Journal. 132 (1): 161–170. arXiv:astro-ph/0603770. Bibcode:2006AJ....132..161G. doi:10.1086/504637. S2CID 250741593.
  4. ^ a b c d e f g h Mesa, D.; Gratton, R.; et al. (February 2023). "AF Lep b: the lowest mass planet detected coupling astrometric and direct imaging data". Astronomy & Astrophysics. 672: A93. arXiv:2302.06213. Bibcode:2023A&A...672A..93M. doi:10.1051/0004-6361/202345865. S2CID 256827302.
  5. ^ Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644.
  6. ^ a b c d e Zhang, Zhoujian; Mollière, Paul; et al. (September 2023). "ELemental abundances of Planets and brown dwarfs Imaged around Stars (ELPIS): I. Potential Metal Enrichment of the Exoplanet AF Lep b and a Novel Retrieval Approach for Cloudy Self-luminous Atmospheres". The Astronomical Journal. 166 (5): 198. arXiv:2309.02488. Bibcode:2023AJ....166..198Z. doi:10.3847/1538-3881/acf768.
  7. ^ a b c d e f g h i j k l Franson, Kyle; Bowler, Brendan P.; et al. (February 2023). "Astrometric Accelerations as Dynamical Beacons: A Giant Planet Imaged Inside the Debris Disk of the Young Star AF Lep". The Astrophysical Journal Letters. 950 (2): L19. arXiv:2302.05420. Bibcode:2023ApJ...950L..19F. doi:10.3847/2041-8213/acd6f6.
  8. ^ a b c Pawellek, Nicole; Wyatt, Mark; et al. (April 2021). "A ~75 per cent occurrence rate of debris discs around F stars in the β Pic moving group". Monthly Notices of the Royal Astronomical Society. 502 (4): 5390–5416. arXiv:2101.12049. Bibcode:2021MNRAS.502.5390P. doi:10.1093/mnras/stab269.
  9. ^ a b c Järvinen, S. P.; Arlt, R.; et al. (February 2015). "Doppler images and the underlying dynamo. The case of AF Leporis". Astronomy & Astrophysics. 574: A25. arXiv:1412.2892. Bibcode:2015A&A...574A..25J. doi:10.1051/0004-6361/201424229. S2CID 119205096.
  10. ^ "V* AF Lep". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 16 February 2023.
  11. ^ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 December 2021.
  12. ^ "Spotting a hidden exoplanet". ESO. 20 February 2023.
  13. ^ a b De Rosa, Robert J.; Nielsen, Eric L.; et al. (February 2023). "Direct imaging discovery of a super-Jovian around the young Sun-like star AF Leporis". Astronomy & Astrophysics. 672: A94. arXiv:2302.06332. Bibcode:2023A&A...672A..94D. doi:10.1051/0004-6361/202345877. S2CID 256827414.
  14. ^ a b Bonse, Markus J.; Gebhard, Timothy D.; et al. (June 2024). "Use the 4S (Signal-Safe Speckle Subtraction): Explainable Machine Learning reveals the Giant Exoplanet AF Lep b in High-Contrast Imaging Data from 2011". arXiv:2406.01809 [astro-ph.EP].
  15. ^ a b Palma-Bifani, P.; Chauvin, G.; et al. (March 2024). "Atmospheric properties of AF Lep b with forward modeling". Astronomy & Astrophysics. 683: A214. arXiv:2401.05491. Bibcode:2024A&A...683A.214P. doi:10.1051/0004-6361/202347653.
  16. ^ Franson, Kyle; Balmer, William O.; Bowler, Brendan P.; Pueyo, Laurent; Zhou, Yifan; Rickman, Emily; Zhang, Zhoujian; Mukherjee, Sagnick; Pearce, Tim D.; Bardalez Gagliuffi, Daniella C.; Biddle, Lauren I.; Brandt, Timothy D.; Bowens-Rubin, Rachel; Crepp, Justin R.; Davidson, James W. (2024-10-01). "JWST/NIRCam 4–5 μm Imaging of the Giant Planet AF Lep b". The Astrophysical Journal. 974 (1): L11. arXiv:2406.09528. Bibcode:2024ApJ...974L..11F. doi:10.3847/2041-8213/ad736a. ISSN 0004-637X.
  17. ^ a b Balmer, William O.; Franson, Kyle; Chomez, Antoine; Pueyo, Laurent; Stolker, Tomas; Lacour, Sylvestre; Nowak, Mathias; Nasedkin, Evert; Bonse, Markus J. (2024-11-08). "VLTI/GRAVITY Observations of AF Lep b: Preference for Circular Orbits, Cloudy Atmospheres, and a Moderately Enhanced Metallicity". arXiv:2411.05917 [astro-ph].
  18. ^ Pearce, Tim D.; Launhardt, Ralf; et al. (March 2022). "Planet populations inferred from debris discs. Insights from 178 debris systems in the ISPY, LEECH, and LIStEN planet-hunting surveys". Astronomy & Astrophysics. 659: A135. arXiv:2201.08369. Bibcode:2022A&A...659A.135P. doi:10.1051/0004-6361/202142720. S2CID 246063879.
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