Astronomy:VHS J1256–1257

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Short description: Low-mass triple star system in the constellation Corvus

Coordinates: Sky map 12h 56m 02.15s, −12° 57′ 21.7″

VHS J125601.92–125723.9
VHS J1256-1257.jpg
Image of VHS 1256-1257 (center) and the b companion (lower right) in the near-infrared
Observation data
Equinox J2000.0]] (ICRS)
Constellation Corvus
Right ascension  12h 56m 02.1337s[1]
Declination −12° 57′ 21.924″[1]
Apparent magnitude (V) 17.759 ± 0.059[2]
Characteristics
VHS J1256–1257AB
Spectral type M7.5 ± 0.5[2]
VHS J1256–1257 b
Spectral type L7.0 ± 1.5[2]
Apparent magnitude (J) 16.662 ± 0.287[2]
Apparent magnitude (H) 15.595 ± 0.209[2]
Apparent magnitude (K) 14.568 ± 0.121[2]
Astrometry
Radial velocity (Rv)−1.4 ± 4.5[2] km/s
Proper motion (μ) RA: −272.462(574)[1] mas/yr
Dec.: −190.239(501)[1] mas/yr
Parallax (π)47.2733 ± 0.4731[1] mas
Distance69.0 ± 0.7 ly
(21.2 ± 0.2 pc)
Details[3]
VHS J1256–1257 AB
Mass94+10
−11 MJup
Luminosity (bolometric)0.0011±0.0002 (10−2.95 ± 0.07) L☉
Temperature2620±140[2] K
Rotation2.0782±0.0004 (A)
2.1342±0.0003 (B)[4]
Rotational velocity (v sin i)75.2+2.7
−2.3[5] km/s
Age140±20[6] Myr
VHS J1256–1257 b
Mass19±5 MJup
Radius1.13–1.21[7] RJup
Luminosity (bolometric)10−4.54 ± 0.07 L☉
Surface gravity (log g)4.55+0.15
−0.11 cgs
Temperature1240±50 K
Rotation22.04±0.05 h[7]
Rotational velocity (v sin i)13.5+3.6
−4.1[5] km/s
Age140±20[6] Myr
Orbit[6]
PrimaryVHS J1256–1257 A
CompanionVHS J1256–1257 B
Period (P)7.31±0.02 yr
Semi-major axis (a)1.96±0.03 AU
Eccentricity (e)0.8826+0.0025−0.0024
Inclination (i)118.7±1.0°
Longitude of the node (Ω)4.4±0.5°
Periastron epoch (T)2021.537+0.015−0.014
Argument of periastron (ω)
(secondary)		44.9±1.0°
Position (relative to VHS J1256–1257AB)[2]
ComponentVHS J1256–1257 b
Epoch of observationMJD 55743.067635 (1 July 2011)
Angular distance8.06 ± 0.03″
Position angle218.1 ± 0.2°
Observed separation
(projected)		102 ± 9 AU
Other designations
VHS J1256–1257AB: GJ 11870(A),11871(B)[8],2MASS J12560215–1257217, TIC 2470992, SIPS J1256–1257, WDS J12560-1257A, WISE J125601.94–125723.7[9]
VHS J1256–1257 b: GJ 11869[8],2MASS J12560183–1257276, TIC 2470993, WDS J12560-1257B, WISEA J125601.66–125728.7[10]
Database references
SIMBADdata
Extrasolar Planets
Encyclopaedia		data

VHS J125601.92–125723.9 (abbreviated to VHS J1256–1257) is a young triple brown dwarf system located in the constellation Corvus approximately 69.0 light-years (21.2 parsecs) from the Sun.[1] The system consists of the equal-mass binary VHS J1256–1257AB and the distant planetary-mass companion VHS 1256–1257 b.[2][11] In 2022, a continuous radio emission from the radiation belts surrounding VHS J1256–1257 was detected.[12]

VHS J1256–1257 b

The VHS J1256–1257 planetary system[6]
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(years) 		Eccentricity Inclination Radius
b 11.8±0.2 MJ 360+110−150 17000+8000−11000 0.73+0.09−0.10 26+12−16° —

VHS 1256–1257 b was first identified and documented by the 2MASS survey in 2015.[2] It orbits at a distance of 350+150
−150 AU and has an estimated mass of approximately 19±5 Jupiter masses.[13][14][15][6]

The planet is carbon-rich, with a C/O molar ratio exceeding 0.63, and its temperature has been measured at 1380±54 K.[16] VHS 1256-1257 b's rotation period has been measured to be 22.04 ± 0.05 hours, which is unusually long for substellar objects.[7][17]

Variability

Observations with Hubble Wide-Field Camera 3 near-infrared time-series spectroscopic observations showed that VHS 1256 b varied with 19.3% at 1.1 and 1.7 μm over 8.5 hours. With the 1.27 μm filter the amplitude was even higher at 24.7%.[17] This is the largest amplitude for any substellar object as of 2022, placing it in the mid-infrared.[7][18] Later studies with the Hubble space telescope have yielded even higher brightness variability of 33-37% without a definite period, indicating a presence of both spots and waves.[19]

Atmospheric composition

Artist's impression of VHS 1256 b in orbit around its host stars VHS J1256–1257AB, based on spectrum made by the JWST

The atmosphere of VHS 1256 b is in a chemical disequilibrium.[18] Carbon monoxide naturally reacts with hydrogen molecules in the atmosphere of brown dwarfs, forming methane and water molecules. The reaction works in both ways, meaning that methane reacts with water and releases hydrogen and carbon monoxide. At higher temperatures and lower pressure the reaction is tilted towards carbon monoxide and at lower temperatures and higher pressure the reaction is tilted towards methane. At equilibrium a cold brown dwarf or planet should have a high concentration of methane and a low concentration of carbon monoxide.[20] The presence of carbon monoxide and depleted methane in the spectrum of VHS 1256 b compared to equilibrium atmospheric models suggests atmospheric mixing. The vertical mixing causes carbon monoxide to rise from lower and hotter atmospheric layers and methane to sink into these lower layers, forcing the upper atmosphere in chemical disequilibrium.[18]

Water and carbon monoxide have both been detected in the atmosphere.[21] The JWST observed the planet in 2022 by taking spectra at a wavelength of 1-20 μm with the instruments NIRSpec and MIRI. The team analysing the data found water vapor, methane, carbon monoxide, carbon dioxide, sodium, potassium and silicate clouds within the atmosphere of VHS 1256 b. The direct detection of silicate clouds is the first such detection reported for a planetary-mass object. The silicates are thought to be made of small amorphous silicate particles. The silicate feature in VHS 1256 b closely matches the silicate feature in the L4.5 brown dwarf 2M2224-0158, detected with Spitzer. The grain size and composition of the silicate clouds in VHS 1256 b will be modelled in the future.[18]

Observations with NIRSpec detected several molecules, as well as several carbon and oxygen isotopes in the atmosphere of VHS 1256 b. The carbon-12 to carbon-13 ratio was measured as 62±2, which is in between that of isolated brown dwarfs (about 100) and that of exoplanets (about 30). Oxygen-17 and oxygen-18 abundances are higher than in the solar system and the local interstellar medium. Isotope abundances are an important tracer of planet formation. The enhancement of minor isotopes in VHS 1256 b could by explained by isotope fractionation in protoplanetary disks. These fractionation processes could be isotope selective photodissociation, gas/ice partitioning and isotopic exchange reactions.[22]

See also

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  2. ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 Gauza, BartoszExpression error: Unrecognized word "etal". (May 2015). "Discovery of a young planetary mass companion to the nearby M dwarf VHS J125601.92-125723.9". The Astrophysical Journal 804 (2): 18. doi:10.1088/0004-637X/804/2/96. 96. Bibcode: 2015ApJ...804...96G. 
  3. ↑ Dupuy, Trent J.Expression error: Unrecognized word "etal". (April 2020). "The Parallax of VHS J1256-1257 from CFHT and Pan-STARRS-1". Research Notes of the AAS 4 (4): 54. doi:10.3847/2515-5172/ab8942. 54. Bibcode: 2020RNAAS...4...54D. 
  4. ↑ Miles-Páez, Paulo A. (2021). "Detection of photometric variability in the very low-mass binary VHS J1256-1257AB using TESS and Spitzer". Astronomy & Astrophysics 651: L7. doi:10.1051/0004-6361/202141203. Bibcode: 2021A&A...651L...7M. 
  5. ↑ 5.0 5.1 Bryan, Marta L.; Benneke, Björn; Knutson, Heather A.; Batygin, Konstatin; Bowler, Brendan P. (December 2018). "Constraints on the spin evolution of young planetary-mass companions". Nature Astronomy 2 (2): 138–144. doi:10.1038/s41550-017-0325-8. Bibcode: 2018NatAs...2..138B. 
  6. ↑ 6.0 6.1 6.2 6.3 6.4 Dupuy, Trent J.; Liu, Michael C.; Evans, Elise L.; Best, William M. J.; Pearce, Logan A.; Sanghi, Aniket; Phillips, Mark W.; Bardalez Gagliuffi, Daniella C. (2023), "On the masses, age, and architecture of the VHS J1256−1257AB b system", Monthly Notices of the Royal Astronomical Society 519 (2): 1688–1694, doi:10.1093/mnras/stac3557, Bibcode: 2023MNRAS.519.1688D 
  7. ↑ 7.0 7.1 7.2 7.3 Zhou, Yifan; Bowler, Brendan P.; Morley, Caroline V.; Apai, Dániel; Kataria, Tiffany; Bryan, Marta L.; Benneke, Björn (August 2020). "Spectral Variability of VHS J1256-1257b from 1 to 5 μm". The Astronomical Journal 160 (2): 77. doi:10.3847/1538-3881/ab9e04. 77. Bibcode: 2020AJ....160...77Z. 
  8. ↑ 8.0 8.1 Golovin, Alex; Reffert, Sabine; Just, Andreas; Jordan, Stefan; Vani, Akash; Jahreiß, Hartmut (November 2022). "The Fifth Catalogue of Nearby Stars (CNS5)". Astronomy & Astrophysics 670: A19. doi:10.1051/0004-6361/202244250. Bibcode: 2023A&A...670A..19G.  Catalogue can be accessed here.
  9. ↑ "VHS J1256-1257 -- Low-mass star (M<1solMass)". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=VHS+J1256-1257. 
  10. ↑ "VHS J1256-1257B -- Brown Dwarf (M<0.08solMass)". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=VHS+J1256-1257B. 
  11. ↑ Stone, Jordan M.Expression error: Unrecognized word "etal". (February 2016). "Adaptive Optics imaging of VHS 1256-1257: A Low Mass Companion to a Brown Dwarf Binary System". The Astrophysical Journal Letters 818 (1): 5. doi:10.3847/2041-8205/818/1/L12. L12. Bibcode: 2016ApJ...818L..12S. 
  12. ↑ Climent, J. B.; Guirado, J. C.; Zapatero Osorio, M. R.; Zakhozhay, O. V.; Pérez-Torres, M.; Azulay, R.; Gauza, B.; Rebolo, R. et al. (2022), "Radio emission in a nearby, ultra-cool dwarf binary: A multifrequency study", Astronomy & Astrophysics 660: A65, doi:10.1051/0004-6361/202142260, Bibcode: 2022A&A...660A..65C 
  13. ↑ Rich, Evan A.Expression error: Unrecognized word "etal". (October 2016). "Thermal Infrared Imaging and Atmospheric Modeling of VHS J125601.92-125723.9 b: Evidence for Moderately Thick Clouds and Equilibrium Carbon Chemistry in a Hierarchical Triple System". The Astrophysical Journal 830 (2): 10. doi:10.3847/0004-637X/830/2/114. 114. Bibcode: 2016ApJ...830..114R. 
  14. ↑ Miles, Brittany E.Expression error: Unrecognized word "etal". (December 2018). "Methane in Analogs of Young Directly Imaged Exoplanets". The Astrophysical Journal 869 (1): 11. doi:10.3847/1538-4357/aae6cd. 18. Bibcode: 2018ApJ...869...18M. 
  15. ↑ Bowler, Brendan P.; Zhou, Yifan; Morley, Caroline V.; Kataria, Tiffany; Bryan, Marta L.; Benneke, Björn; Batygin, Konstatin (April 2018). "Strong Near-infrared Spectral Variability of the Young Cloudy L Dwarf Companion VHS J1256-1257 b". The Astrophysical Journal Letters 893 (2): 7. doi:10.3847/2041-8213/ab8197. L30. Bibcode: 2020ApJ...893L..30B. 
  16. ↑ Petrus, Simon; Chauvin, Gaël; Bonnefoy, Mickaël; Tremblin, Pascal; Charnay, Benjamin; Delorme, Philippe; Marleau, Gabriel-Dominique; Bayo, Amelia et al. (2023), "X-SHYNE: X-shooter spectra of young exoplanet analogs", Astronomy & Astrophysics 670: L9, doi:10.1051/0004-6361/202244494 
  17. ↑ 17.0 17.1 Bowler, Brendan P.; Zhou, Yifan; Morley, Caroline V.; Kataria, Tiffany; Bryan, Marta L.; Benneke, Björn; Batygin, Konstantin (2020-04-01). "Strong Near-infrared Spectral Variability of the Young Cloudy L Dwarf Companion VHS J1256-1257 b". The Astrophysical Journal 893 (2): L30. doi:10.3847/2041-8213/ab8197. ISSN 0004-637X. Bibcode: 2020ApJ...893L..30B. 
  18. ↑ 18.0 18.1 18.2 18.3 Miles, Brittany E.Expression error: Unrecognized word "et". (2023). "The JWST Early-release Science Program for Direct Observations of Exoplanetary Systems II: A 1 to 20 μm Spectrum of the Planetary-mass Companion VHS 1256–1257 B". The Astrophysical Journal Letters 946 (1): L6. doi:10.3847/2041-8213/acb04a. Bibcode: 2023ApJ...946L...6M. 
  19. ↑ Zhou, Yifan; Bowler, Brendan P.; Apai, Dániel; Kataria, Tiffany; Morley, Caroline V.; Bryan, Marta L.; Skemer, Andrew J.; Benneke, Björn (2022), "Roaring Storms in the Planetary-mass Companion VHS 1256-1257 b: Hubble Space Telescope Multi-epoch Monitoring Reveals Vigorous Evolution in an Ultracool Atmosphere", The Astronomical Journal 164 (6): 239, doi:10.3847/1538-3881/ac9905, Bibcode: 2022AJ....164..239Z 
  20. ↑ Zahnle, Kevin J.; Marley, Mark S. (2014-12-01). "Methane, Carbon Monoxide, and Ammonia in Brown Dwarfs and Self-Luminous Giant Planets". The Astrophysical Journal 797 (1): 41. doi:10.1088/0004-637X/797/1/41. ISSN 0004-637X. Bibcode: 2014ApJ...797...41Z. https://ui.adsabs.harvard.edu/abs/2014ApJ...797...41Z. 
  21. ↑ Hoch, Kielan K. W.; Konopacky, Quinn M.; Barman, Travis S.; Theissen, Christopher A.; Brock, Laci; Perrin, Marshall D.; Ruffio, Jean-Baptiste; Macintosh, Bruce et al. (2022), "Moderate-resolution K-band Spectroscopy of the Substellar Companion VHS 1256 B", The Astronomical Journal 164 (4): 155, doi:10.3847/1538-3881/ac84d4, Bibcode: 2022AJ....164..155H 
  22. ↑ Gandhi, Siddharth; de Regt, Sam; Snellen, Ignas; Zhang, Yapeng; Rugers, Benson; van Leur, Niels; Bosschaart, Quincy (9 Nov 2023). "JWST measurements of 13C, 18O and 17O in the atmosphere of super-Jupiter VHS 1256 b". The Astrophysical Journal Letters 957 (2): 11. doi:10.3847/2041-8213/ad07e2. Bibcode: 2023ApJ...957L..36G. 

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