Astronomy:HD 28736

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Short description: Star system in the constellation Taurus
HD 28736
Location of HD 28736 (circled)
Observation data
{{#ifeq:J2000|J2000.0 (ICRS)|Epoch J2000.0      Equinox J2000.0 (ICRS)| Epoch J2000      [[Astronomy:Equinox (celestial coordinates)|Equinox J2000}}
Constellation Taurus[1]
HD 28736 A
Right ascension  04h 32m 04.80859s[2]
Declination +05° 24′ 36.1482″[2]
Apparent magnitude (V) 6.352[3]
HD 28736 C
Right ascension  04h 33m 56.59566s[4]
Declination +05° 37′ 23.5351″[4]
Apparent magnitude (V) {{{appmag_v2}}}
Characteristics
Spectral type (F5V + L9-T1) + L0/1[5]
B−V color index +0.431[6]
Astrometry
HD 28736 A
Radial velocity (Rv)39.5813 ± 0.0216[7] km/s
Proper motion (μ) RA: 112.174[2] mas/yr
Dec.: 7.756[2] mas/yr
Parallax (π)23.1089 ± 0.0278[2] mas
Distance141.1 ± 0.2 ly
(43.27 ± 0.05 pc)
Absolute magnitude (MV)3.18[1]
HD 28736 C
Proper motion (μ) RA: 107.173[4] mas/yr
Dec.: 7.595[4] mas/yr
Parallax (π)22.6203 ± 0.4505[4] mas
Distance144 ± 3 ly
(44.2 ± 0.9 pc)
Orbit[5]
PrimaryHD 28736 A
CompanionHD 28736 B
Period (P)60+30
−16 yr
Semi-major axis (a)0.37"
(17+5
−4 astronomical unit|AU)
Eccentricity (e)0.36+0.37
−0.25
Inclination (i)95.3+3.9
−2.1°
Orbit[5]
PrimaryHD 28736 A
CompanionHD 28736 C
Semi-major axis (a)1837"
(79000 astronomical unit|AU)
Details[5]
HD 28736 A
Mass1.40±0.05 M☉
Surface gravity (log g)4.3±0.2 cgs
Temperature6655±125 K
Metallicity [Fe/H]0.13±0.05 dex
Rotational velocity (v sin i)45.6±1.8 km/s
Age650±100 Myr
HD 28736 B
Mass24+6
−4 MJup
Surface gravity (log g)4.5 cgs
Temperature1300±50 K
HD 28736 C
Mass73±7 MJup
Luminosity2.40+0.23
−0.21×10−4 L☉
Other designations
HD 28736 AB: BD+05°674, GC 5531, HD 28736, HIP 21152, HR 1436, SAO 111879, PPM 147652, TYC 90-33-1, GSC 00090-00033, 2MASS J04320481+0524359[8][9]
HD 28736 C: 2MASS J04335658+0537235, WISE J043356.65+053723.5[10]
Database references
SIMBADHD 28736
B
C

HD 28736 (HIP 21152, HR 1436) is a triple star system in the constellation of Taurus. It is composed of an F-type main-sequence star, an orbiting low-mass brown dwarf or giant planet, and a high-mass brown dwarf or low-mass star. Located some 141 light-years (43 parsecs) away according to Gaia DR3 parallax measurements, it is a member of the Hyades cluster, moving away from Earth at a heliocentric radial velocity of 39.58 km/s. With an apparent magnitude of 6.352, it is near the limit for naked eye visibility under dark skies.

Stellar components

HD 28736 A

HD 28736 A is a young star, aged 650 ± 100 million years. This was estimated from the age of the Hyades cluster itself,[5] which is about 625 million years.[11] It is about 40% more massive than the Sun and also hotter at 6,655 K (6,382 °C; 11,519 °F).

The star is enriched in many elements heavier than hydrogen and helium compared to the Sun. In particular, the concentrations of strontium, barium, lanthanum, cerium, samarium, and gadolinium are at least 150% greater. A similar pattern is observed in other F-type dwarfs belonging to the cluster.[12]

HD 28736 B

In 2022, three teams of astronomers independently announced the discovery of a brown dwarf orbiting HD 28736 A via direct imaging, the first brown dwarf to be discovered by this method around main-sequence stars in the Hyades[5][13] and the first substellar object of any kind to be found in the cluster to orbit stars with a spectral type of F, G, or K.[14]

The object, HD 28736 B, is near the border between L and T dwarfs, with an estimated spectral type of T0 ± 1. It has a mass of 24 |♃|J}}}}}} (~2% of the host star mass[13]), substantially lower than evolutionary model predictions[5] and close to the planet-brown dwarf boundary.[13] Indeed, some organizations classify it as a planet instead, such as the NASA Exoplanet Science Institute, which includes the object in the NASA Exoplanet Archive[15][lower-alpha 1] since it weighs less than 30 MJ.[16] It completes one orbit around the star every 60 years at a distance of 17 AU (2.5×10^9 km), slightly closer than Uranus is to the Sun (19.165 AU[17]).

HD 28736 C

One of the teams that discovered HD 28736 B reported that another object, 2MASS J04335658+0537235, was found to be a co-moving companion to the HD 28736 system, at a very wide projected separation of 79,000 AU (1.25 ly) at the host star's distance. The 3D separation is even larger at 250000±140000 AU (4.0±2.2 ly), comparable to the distance between the Sun and Alpha Centauri. Despite this, there is a high likelihood that the object is gravitationally bound to the system.[5]

It has a mass of 73±7 MJ, placing it right at the hydrogen burning limit. As such, it is uncertain whether the object is a massive brown dwarf or a low-mass star.[5]

Nearby interstellar clouds

Observations via the Space Telescope Imaging Spectrograph, installed on the Hubble Space Telescope, revealed three distinct velocity components in the interstellar absorption seen in HD 28736's spectra, specifically in the emission lines of singly ionized magnesium (Mg II in spectroscopic notation). This corresponds to three interstellar clouds occupying the space between the system and Earth, all moving in different directions and speeds.[18]

The closest of the three is the Local Interstellar Cloud (LIC), which the Solar System is within and thus absorbs light emitted by all Hyades members. A secondary cloud, dubbed the Hyades Cloud, is located farther than the LIC and possesses a more filament-like structure, absorbing light from a substantial portion of Hyades stars. A third cloud has been identified that affects light from HD 28736 but not other stars in the vicinity, meaning it only covers a small patch of the sky and hence is probably situated farther away than the Hyades Cloud.[18]

Notes

  1. ↑ The NASA Exoplanet Archive lists the object as HIP 21152 b, rather than using the capital B.

References

  1. ↑ 1.0 1.1 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 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.
  3. ↑ Joner, Michael D.; Taylor, Benjamin J.; Laney, C. David; Van Wyk, Francois (2006). "Homogeneous Photometry for the Hyades: Scale-Factor and Zero-Point Tests of Previously Published BV(RI)C Photometry". The Astronomical Journal 132 (1): 111. doi:10.1086/504410. Bibcode: 2006AJ....132..111J. 
  4. ↑ 4.0 4.1 4.2 4.3 4.4 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.
  5. ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 Franson, Kyle; Bowler, Brendan P.; Bonavita, Mariangela et al. (2023-01-09). "Astrometric Accelerations as Dynamical Beacons: Discovery and Characterization of HIP 21152 B, the First T-dwarf Companion in the Hyades*". The Astronomical Journal (American Astronomical Society) 165 (2): 39. doi:10.3847/1538-3881/aca408. ISSN 0004-6256. Bibcode: 2023AJ....165...39F. 
  6. ↑ Joner, Michael D.; Taylor, Benjamin J.; Laney, C. David et al. (2006-06-02). "Homogeneous Photometry for the Hyades: Scale-Factor and Zero-Point Tests of Previously Published BV(RI)C Photometry". The Astronomical Journal (American Astronomical Society) 132 (1): 111–116. doi:10.1086/504410. ISSN 0004-6256. Bibcode: 2006AJ....132..111J. 
  7. ↑ Leão, I C; Pasquini, L; Ludwig, H-G; de Medeiros, J R (2018-11-29). "Spectroscopic and astrometric radial velocities: Hyades as a benchmark". Monthly Notices of the Royal Astronomical Society (Oxford University Press (OUP)) 483 (4): 5026–5041. doi:10.1093/mnras/sty3215. ISSN 0035-8711. Bibcode: 2019MNRAS.483.5026L. 
  8. ↑ "HD 28736". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+28736. 
  9. ↑ Pilcher, Frederick. "Uranometria Argentina". http://www.uranometriaargentina.com/. 
  10. ↑ "2MASS J04335658+0537235". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=2MASS+J04335658%2B0537235. 
  11. ↑ Perryman, M.A.C. (1998). "The Hyades: distance, structure, dynamics, and age". Astronomy & Astrophysics 331: 81–120. Bibcode: 1998A&A...331...81P. 
  12. ↑ Kılıçoǧlu, T.; Monier, R.; Gebran, M. (December 2015). Martins, F.; Boissier, S.; Buat, V. et al.. eds. "Abundance Determinations for the F Dwarfs Members of the Hyades from SOPHIE High Resolution Spectra". Proceedings of the Annual Meeting of the French Society of Astronomy and Astrophysics: 389–392. Bibcode: 2015sf2a.conf..389K. 
  13. ↑ 13.0 13.1 13.2 Kuzuhara, Masayuki; Currie, Thayne; Takarada, Takuya et al. (2022-07-27). "Direct-imaging Discovery and Dynamical Mass of a Substellar Companion Orbiting an Accelerating Hyades Sun-like Star with SCExAO/CHARIS*". The Astrophysical Journal Letters (American Astronomical Society) 934 (2): L18. doi:10.3847/2041-8213/ac772f. ISSN 2041-8205. Bibcode: 2022ApJ...934L..18K. 
  14. ↑ Bonavita, M; Fontanive, C; Gratton, R et al. (2022-05-10). "Results from The COPAINS Pilot Survey: Four new brown dwarfs and a high companion detection rate for accelerating stars". Monthly Notices of the Royal Astronomical Society (Oxford University Press (OUP)). doi:10.1093/mnras/stac1250. ISSN 0035-8711. 
  15. ↑ "HIP 21152 Overview". NASA Exoplanet Archive. https://exoplanetarchive.ipac.caltech.edu/overview/HIP%2021152. 
  16. ↑ "Exoplanet Criteria for Inclusion in the Archive". NASA Exoplanet Archive. http://exoplanetarchive.ipac.caltech.edu/docs/exoplanet_criteria.html. 
  17. ↑ Williams, Dr. David R. (31 January 2005). "Uranus Fact Sheet". NASA. https://nssdc.gsfc.nasa.gov/planetary/factsheet/uranusfact.html. 
  18. ↑ 18.0 18.1 Redfield, Seth; Linsky, Jeffrey L. (2001-04-10). "Microstructure of the Local Interstellar Cloud and the Identification of the Hyades Cloud". The Astrophysical Journal (American Astronomical Society) 551 (1): 413–428. doi:10.1086/320096. ISSN 0004-637X. Bibcode: 2001ApJ...551..413R. 



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