EBLM J0555-57

EBLM J0555-57 is a triple star system approximately 670 light-years from Earth. EBLM J0555-57Ab, the smallest star in the system, orbits its primary star with a period of 7.8 days, and at the time of discovery, was the smallest known star with a mass sufficient to enable the fusion of hydrogen in its core.

EBLM J0555-57AB

Resolved image of EBLM J0555-57A (left) and EBLM J0555-57B (right) taken with the Leonhard Euler Telescope at the ESO's La Silla Observatory[1]
Credit: ESO
Observation data
Epoch J2000      Equinox J2000
Constellation Pictor
EBLM J0555-57A
Right ascension 05h 55m 32.6885s[2]
Declination −57° 17′ 26.067″[2]
Apparent magnitude (V) 9.98[1]
EBLM J0555-57B
Right ascension 05h 55m 32.3944s[3]
Declination −57° 17′ 26.748″[3]
Apparent magnitude (V) 10.76[1]
Characteristics
EBLM J0555-57A
Spectral type F8[4]
Variable type Eclipsing[1]
EBLM J0555-57B
Spectral type G0V
Astrometry
EBLM J0555-57A
Radial velocity (Rv)18.66±0.74[5] km/s
Proper motion (μ) RA: 2.972[2] mas/yr
Dec.: −39.532[2] mas/yr
Parallax (π)4.8611 ± 0.0137 mas[2]
Distance671 ± 2 ly
(205.7 ± 0.6 pc)
EBLM J0555-57B
Proper motion (μ) RA: 2.838[3] mas/yr
Dec.: −38.344[3] mas/yr
Parallax (π)4.8747 ± 0.0175 mas[3]
Distance669 ± 2 ly
(205.1 ± 0.7 pc)
Position (relative to A)
ComponentB
Epoch of observation1998
Angular distance2.50″ [4]
Position angle254° [4]
Observed separation
(projected)		479 AU [1]
Orbit[1]
PrimaryAa
CompanionAb
Period (P)7.757676+0.000029
−0.000025 d
Semi-major axis (a)0.0817±0.0019 au
Eccentricity (e)0.0894+0.0035
−0.0036
Inclination (i)89.84+0.2
−1.8°
Argument of periastron (ω)
(secondary)		−53.7+1.5
−1.8°
Details[1]
EBLM J0555-57Aa
Mass1.13±0.08[1] M☉
Radius0.99+0.15
−0.03[1] R☉
Luminosity3.245[6] L☉
Surface gravity (log g)4.18±0.21[1] cgs
Temperature6,461±124[1] K
Metallicity [Fe/H]−0.24±0.16[1] dex
Rotational velocity (v sin i)7.60±0.28[1] km/s
Age1.6±1.2[7] Gyr
EBLM J0555-57Ab
Mass85.2+4.0
−3.9[1] MJup
Radius0.84+0.14
−0.04[1] RJup
Surface gravity (log g)5.50+0.03
−0.13[1] cgs
EBLM J0555-57B
Mass1.01[8] M☉
Radius0.94±0.08[1] R☉
Luminosity1.501[9] L☉
Surface gravity (log g)4.37[8] cgs
Temperature5,717±124[1] K
Metallicity [Fe/H]−0.38[8] dex
Other designations
CD−57 1311, CPD−57 913, WDS J05555-5717, TYC 8528-926, 2MASS J05553262-5717261
Database references
SIMBADdata

System
A z' band light curve for EBLM J0555-57, adapted from von Boetticher et al. (2017)[1]

EBLM J0555-57, also known as CD−57 1311, is a triple star system[1][10] in the constellation Pictor, which contains a visual binary system consisting of two sun-like stars separated by 2.5": EBLM J0555-57Aa, a magnitude 9.98 spectral type F8 star, and EBLM J0555-57B, a magnitude 10.76 star. No orbital motion has been detected but they have almost identical radial velocities and are assumed to be gravitationally bound.[1]

Component A of the system is itself an eclipsing binary (EBLM J0555-57Ab orbiting EBLM J0555-57Aa). Eclipses, also known as transits in the context of planetary searches, have been detected in the near infrared, with brightness drops of 0.05% during the eclipse. The shape and duration of the transits allow the radii of the two stars to be determined. A full solution of the orbit gives a period of 7 days and 18 hours, with a low eccentricity of 0.09, an almost edge-on inclination of 89.84°, and a semi-major axis of 0.08 AU.[1]

EBLM J0555-57Ab

EBLM J0555-57Ab has a mass of about 85.2±4 Jupiter masses, or 0.081 solar masses. Its radius is 0.08 solar radii (about 59,000 km), comparable to Saturn, which has an equatorial radius of 60,268 km. The star is about 250 times more massive than Saturn.[1] Current stellar models put its mass at the lower limit for hydrogen-burning stars. EBLM J0555-57Ab was discovered by a group of scientists at the University of Cambridge associated with the EBLM project (Eclipsing Binary, Low Mass),[1] using data collected by the WASP project. WASP (Wide Angle Search for Planets) is searching for exoplanets using the transit method.[11] Additional properties of the star were determined using Doppler spectroscopy, to measure the periodic radial velocity variation of the primary star due to the gravitational influence of its companion.[1]

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EBLM J0555-57Ab is the smallest hydrogen burning star currently known.

See also

References
  1. von Boetticher, Alexander; Triaud, Amaury H. M. J.; Queloz, Didier; Gill, Sam; Lendl, Monika; Delrez, Laetitia; Anderson, David R.; Collier Cameron, Andrew; Faedi, Francesca; et al. (2017). "The EBLM project III. A Saturn-size low-mass star at the hydrogen-burning limit". Astronomy and Astrophysics. 1706: L6. arXiv:1706.08781. Bibcode:2017A&A...604L...6V. doi:10.1051/0004-6361/201731107. S2CID 54610182.
  2. Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  3. Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  4. Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal. 122 (6): 3466. Bibcode:2001AJ....122.3466M. doi:10.1086/323920.
  5. Kunder, Andrea; Kordopatis, Georges; Steinmetz, Matthias; Zwitter, Tomaž; McMillan, Paul J.; Casagrande, Luca; Enke, Harry; Wojno, Jennifer; Valentini, Marica; Chiappini, Cristina; Matijevič, Gal; Siviero, Alessandro; De Laverny, Patrick; Recio-Blanco, Alejandra; Bijaoui, Albert; Wyse, Rosemary F. G.; Binney, James; Grebel, E. K.; Helmi, Amina; Jofre, Paula; Antoja, Teresa; Gilmore, Gerard; Siebert, Arnaud; Famaey, Benoit; Bienaymé, Olivier; Gibson, Brad K.; Freeman, Kenneth C.; Navarro, Julio F.; Munari, Ulisse; et al. (2017). "The Radial Velocity Experiment (RAVE): Fifth Data Release". The Astronomical Journal. 153 (2): 75. arXiv:1609.03210. Bibcode:2017AJ....153...75K. doi:10.3847/1538-3881/153/2/75. S2CID 118835808.
  6. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  7. von Boetticher, Alexander; et al. (2019). "The EBLM Project". Astronomy & Astrophysics. 625: A150. arXiv:1903.10808. Bibcode:2019A&A...625A.150V. doi:10.1051/0004-6361/201834539. S2CID 85517239.
  8. Anders, F.; Khalatyan, A.; Queiroz, A. B. A.; Chiappini, C.; Ardevol, J.; Casamiquela, L.; Figueras, F.; Jimenez-Arranz, O.; Jordi, C.; Monguio, M.; Romero-Gomez, M.; Altamirano, D.; Antoja, T.; Assaad, R.; Cantat-Gaudin, T.; Castro-Ginard, A.; Enke, H.; Girardi, L.; Guiglion, G.; Khan, S.; Luri, X.; Miglio, A.; Minchev, I.; Ramos, P.; Santiago, B. X.; Steinmetz, M. (2022). "VizieR Online Data Catalog: StarHorse2, Gaia EDR3 photo-astrometric distances (Anders+, 2022)". Vizier Online Data Catalog. Bibcode:2022yCat.1354....0A.
  9. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  10. Wenz, John (11 July 2017). "This Is the Smallest Star Ever Discovered". Popular Mechanics. Retrieved 17 July 2017.
  11. "Smallest-ever star discovered by astronomers". Phys.org. 12 July 2017. Retrieved 12 July 2017.
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