HD 984 is a star located in the constellation Cetus. It is a F-type main-sequence star with a brown dwarf companion, called HD 984 B. The companion is orbiting HD 984 at a distance of 28 AU and has a mass of 61 MJ and a temperature of 2730 K. HD 984 itself has a mass of 1.2 M☉, a temperature of 6326 K, and a radius of 1.247 R☉. The age of the system is estimated to be between 30 and 200 million years. The stars are located 148.7 light-years away, based on data from Gaia DR3.
Characteristics edit
The HD 984 system is located in the equatorial constellation Cetus, as based on its astronomical coordinates RA 00h 14m 10.25s, DEC −07° 11′ 56.82″.[1][c] The apparent magnitude of HD 984, i.e. its relative brightness to Earth, is 7.32. Such brightness is lower than the limit for naked-eye visibility, generally defined as 6.5m,[7] meaning that HD 984 can't be seen with the naked eye. The absolute magnitude, i.e. the magnitude of HD 984 if it was seen at 10 parsecs (32.6 ly), is 3.95.[4]
The distance to HD 984 is about 149 light-years, based on Gaia DR3 data.[1] Kinematically, it is part of the Columba group.[4][8] The system has a relatively high proper motion.[4] The age of the HD 984 system is likely to be less than 200 million years, based on HD 984 A's rotation and stellar activity. Ages less than 30 million years can be ruled out, based the isochronal age constraints for HD 984 B.[4]
HD 984 A edit
HD 984 A is a F-type main-sequence star with a spectral type of F7V.[2][4] It is 20% more massive than the Sun and 25% larger.[4] The effective temperature of HD 984 A is 6,326 K (6,053 °C),[3] 464 degrees hotter than the Sun,[note 2] and its luminosity is equivalent to 2.21 times the solar luminosity.[6][d] It is one of the fastest-rotating stars, with a rotation period estimated to be less than 1.6 days (38 hours), which is faster than 99% of all stars.[3] The Sun's rotational period is 27 days for comparison.
Its rotation, coronal activity and cromospheric activity indicates that it is a young and active main-sequence star.[4] Its age is very likely to less than 200 millon years, based on its rotation and activity indicators.[4] The star is expected to live 5 billion years on the main sequence.[4]
HD 984 B edit
HD 984 B is a brown dwarf, a class of astronomical objects that are intermediate between planets and stars, having masses between 13 and 75 MJ, and, unlike stars, can't produce thermonuclear fusion of hydrogen.[9] It was discovered in 2015, using direct imaging from the Apodizing Phase Plate coronagraph at the Very Large Telescope with NaCo. The discovery was announced by Meshkat et al.[4]
Its mass was firstly estimated using the age of the system, by Meshkat et al. (2015) and Jonson-Groh et al. (2017).[6][4] Mass estimates of HD 984 B range from 34 MJ to 94 MJ, assuming ages of 30 and 200 million years respectively.[6] Assuming the largest mass and age, HD 984 B would be in the stellar mass regime.[5] A 2022 study found a dynamical mass of 61±4 MJ, which places HD 984 B in the brown dwarf regime at 99.7% confidence.[5] This mass was obtained using astrometric acceleration, new direct imaging of the object and radial velocity measurements, and is consistent with evolutionary models.[5]
HD 984 B has an effective temperature of 2,730 K (2,460 °C) and a luminosity of 1.32% (0.00132) of the solar luminosity.[6] A radius of 0.162 R☉ (1.576 RJ) is calculated using the luminosity and temperature. The spectral type is M6.5±1.5, which makes HD 984 B in the M spectral type.[6] The metalicity of the companion, i.e. the abundance of elements other than hydrogen and helium, is −0.62±0.02 dex, which is equivalent to one-fourth of the solar metalicity.[3]
HD 984 B is orbiting HD 984 A at a mean distance of 28 AU (4.2×109 km),[5] which is about the same distance of Neptune to the Sun. It has an orbital period of 140 years and an eccentric orbit (e = 0.76±0.05).[5] The orbital eccentricity causes the distance of HD 984 B to the host star to vary from 6.72 to 49.3 AU.[e] The orbital inclination of HD 984 B is of 121 degrees.[5]
Further reading edit
- Meshkat, T.; Bonnefoy, M.; Mamajek, E. E.; Quanz, S. P.; Chauvin, G.; Kenworthy, M. A.; Rameau, J.; Meyer, M. R.; Lagrange, A.-M.; Lannier, J.; Delorme, P. (2015-11-01). "Discovery of a low-mass companion to the F7V star HD 984". Monthly Notices of the Royal Astronomical Society. 453 (3): 2379–2387. doi:10.1093/mnras/stv1732. ISSN 0035-8711.
- Johnson-Groh, Mara; Marois, Christian; De Rosa, Robert J.; Nielsen, Eric L.; Rameau, Julien; Blunt, Sarah; Vargas, Jeffrey; Ammons, S. Mark; Bailey, Vanessa P.; Barman, Travis S.; Bulger, Joanna; Chilcote, Jeffrey K.; Cotten, Tara; Doyon, René; Duchêne, Gaspard (2017-04-01). "Integral Field Spectroscopy of the Low-mass Companion HD 984 B with the Gemini Planet Imager". The Astronomical Journal. 153: 190. doi:10.3847/1538-3881/aa6480. ISSN 0004-6256.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - Franson, Kyle; Bowler, Brendan P.; Brandt, Timothy D.; Dupuy, Trent J.; Tran, Quang H.; Brandt, G. Mirek; Li, Yiting; Kraus, Adam L. (2022-02-01). "Dynamical Mass of the Young Substellar Companion HD 984 B". The Astronomical Journal. 163 (2): 50. doi:10.3847/1538-3881/ac35e8. ISSN 0004-6256.
{{cite journal}}: CS1 maint: unflagged free DOI (link)
References edit
- ^ a b c d e f g h i 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.
- ^ a b c d e f g "HD 984". SIMBAD. Centre de données astronomiques de Strasbourg.
- ^ a b c d e f g h Costes, J. C.; Xuan, J. W.; Vigan, A.; Wang, J.; D'Orazi, V.; Mollière, P.; Baker, A.; Bartos, R.; Blake, G. A. (2024-04-17), Fresh view of the hot brown dwarf HD 984 B through high-resolution spectroscopy, doi:10.48550/arXiv.2404.11523, retrieved 2024-04-19
- ^ a b c d e f g h i j k l m n o p q r Meshkat, T.; Bonnefoy, M.; Mamajek, E. E.; Quanz, S. P.; Chauvin, G.; Kenworthy, M. A.; Rameau, J.; Meyer, M. R.; Lagrange, A.-M.; Lannier, J.; Delorme, P. (2015-11-01). "Discovery of a Low-Mass Companion to the F7V star HD 984". Monthly Notices of the Royal Astronomical Society. 453 (3): 2379–2387. doi:10.1093/mnras/stv1732. ISSN 0035-8711.
- ^ a b c d e f g h Franson, Kyle; Bowler, Brendan P.; Brandt, Timothy D.; Dupuy, Trent J.; Tran, Quang H.; Brandt, G. Mirek; Li, Yiting; Kraus, Adam L. (2022-02-01). "Dynamical Mass of the Young Substellar Companion HD 984 B". The Astronomical Journal. 163 (2): 50. doi:10.3847/1538-3881/ac35e8. ISSN 0004-6256.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - ^ a b c d e f g h i j Johnson-Groh, Mara; Marois, Christian; De Rosa, Robert J.; Nielsen, Eric L.; Rameau, Julien; Blunt, Sarah; Vargas, Jeffrey; Ammons, S. Mark; Bailey, Vanessa P.; Barman, Travis S.; Bulger, Joanna; Chilcote, Jeffrey K.; Cotten, Tara; Doyon, René; Duchêne, Gaspard (2017-04-01). "Integral Field Spectroscopy of the Low-mass Companion HD 984 B with the Gemini Planet Imager". The Astronomical Journal. 153: 190. doi:10.3847/1538-3881/aa6480. ISSN 0004-6256.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - ^ Curtis, Heber Doust (1903-01-01). "On the limits of unaided vision". Lick Observatory Bulletin. 38: 67–69. doi:10.5479/ADS/bib/1903LicOB.2.67C. ISSN 0075-9317.
- ^ Nielsen, E. L.; De Rosa, R.; Macintosh, B.; Wang, J.; Ruffio, J.; Chiang, E.; Marley, M.; Saumon, D.; Savransky, D.; Gemini Planet Imager Exoplanet Survey Team (2020-01-01). "The Gemini Planet Imager Exoplanet Survey: Giant Planet and Brown Dwarf Demographics from 10-100 AU". 235: 280.02.
{{cite journal}}: Cite journal requires|journal=(help) - ^ "Brown dwarf | Astronomy, Formation & Characteristics | Britannica". www.britannica.com. 2024-04-22. Retrieved 2024-04-24.
- ^ Calculated from a temperature of 2730 K and a luminosity logarithm of -2.88.
- ^ From a logarithm of -2.88.
- ^ Based on the coordinates placed on this website.
- ^ Using a luminosity logarithm of 0.346.
- ^ Calculated using the semi-major axis and the obrital eccentricity.
28×(1-0.76) = 6.72 AU.
28×(1+0.76) = 49.28 AU.
Cite error: There are <ref group=note> tags on this page, but the references will not show without a {{reflist|group=note}} template (see the help page).