HD 16754

HD 16754
Location of HD 16754 (circled in red)
Observation data
Epoch J2000      Equinox ICRS
Constellation Eridanus
Right ascension 02h 39m 47.97s
Declination −42° 53′ 30.4″
Apparent magnitude (V) +4.74
Characteristics
Spectral type A1 Vb
B−V color index 0.061±0.003
Astrometry
Radial velocity (Rv)+18.0±4.2 km/s
Proper motion (μ) RA: +92.11 mas/yr
Dec.: −17.82 mas/yr
Parallax (π)25.15±0.61 mas
Distance131.77 ± 0.33 ly
(40.4±0.1 pc)
Absolute magnitude (MV)+1.76
Details
s Eri Aa
Mass2.0 M☉
Radius1.7 R☉
Luminosity17.44 L☉
Surface gravity (log g)4.40±0.14 cgs
Temperature9,000 K
Metallicity [Fe/H]−0.06 dex
Rotational velocity (v sin i)167.6±1.7 or 13.4±1.5 km/s
Age160 Myr
s Eri Ab1
Mass0.92 M☉
Radius0.82 R☉
Temperature5,400 K
Age160 Myr
s Eri Ab2
Mass0.84 M☉
Radius0.75 R☉
Temperature5,100 K
Age160 Myr
Other designations
s Eri, CD−43°814, FK5 2185, HD 16754, HIP 12413, HR 789, SAO 215996
Database references
SIMBADdata

HD 16754 is a triple star system in the constellation Eridanus. It has the Bayer designation s Eridani; HD 16754 is the designation from the Henry Draper catalogue. The system is visible to the naked eye as a faint point of light with an apparent visual magnitude of +4.74. It is located 40.4 ± 0.1 parsecs (131.77 ± 0.33 ly) away and is drifting further away with a radial velocity of +18 km/s.

Characteristics

s Eridani was flagged as an astrometric binary based on proper motion measurements made from the Hipparcos spacecraft. Interferometric observations gathered in 2026 revealed it to be an hierarchical triple star system, with the primary star orbited by an inner binary. The components of the inner binary were found to be separated by a projected separation of 0.22 au, while the overall system has a projected separation of 4.6 au. If these values are close to the semi-major axis, combining them and the components' masses in Kepler's third law would imply orbital periods of roughly one month and five years for the inner and outer systems, respectively. The expected timescale of the Kozai mechanism is of 300 years, short enough for changes in the inner system's eccentricity and inclination to be detected in a timescale of a decade.

The primary component, s Eridani Aa, is an A-type main-sequence star with a stellar classification of A1 Vb. It has 2.0 times the mass and 1.7 times the radius of the Sun, with an effective temperature of 9000 K. Earlier measurements showed a high projected rotational velocity of 168 km/s. However, Ammler-von Eiff and Reiners (2012) found a much lower velocity of 13 km/s. The secondary and tertiary components, named s Eridani Ab1 and Ab2, are slightly smaller and cooler than the Sun, with masses of 0.92 and 0.84 M☉, radii of 0.82 and 0.75 R☉, and temperatures of 5,400 and 5,100 K, respectively. The presence of young solar-type stars explain the presence of hard X-ray emission coming from the system, which would not be expected for an A-type star.

The system has been considered to be a member of the Columba association of co-moving stars, which would give it an age of 30 million years, the same as the cluster. However, according to stellar isochrones the system has an age estimated at 160 million years, arguing against membership to the association.

s Eridani makes a wide sextuple system with two optical companions. Component B is separated by 25.3″ from the inner triple, implying a projected separation of a hundred au. It is a binary system itself, consisting of two red dwarfs with masses of 0.36 and 0.31 M☉. It has a combined class in the range M2-5V and is a source of X-ray emission with a luminosity of 924×1020 W. The outer companion (D) is also a red dwarf, with a mass of 0.14 M☉. It is separated by 10.9′ from the inner pair, implying a projected separation of 26,000 au.

References

  1. ↑ Roman, Nancy G. (1987). "Identification of a constellation from a position". Publications of the Astronomical Society of the Pacific. 99 (617): 695. Bibcode:1987PASP...99..695R. doi:10.1086/132034. Constellation record for this object at VizieR.
  2. 1 2 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.
  3. 1 2 3 4 5 6 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.
  4. 1 2 3 Gray, R. O.; 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 119476992.
  5. 1 2 3 EAS (1997). "The HIPPARCOS and TYCHO catalogues". Astrometric and Photometric Star Catalogues Derived from the ESA Hipparcos Space Astrometry Mission. ESA SP Series. 1200. Noordwijk, Netherlands: ESA Publications Division. Bibcode:1997ESASP1200.....E. ISBN 9290923997. Retrieved 15 October 2022.{{cite journal}}: CS1 maint: periodical has ISBN (link)
  6. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Waisberg, Idel; Klein, Ygal; Katz, Boaz (2026-07-24), "Hidden Companions to Intermediate-mass Stars. XXXVIII. Upgraded Multiplicity 3 → 6 s Eridani (HIP 12413) is a Compact Triple within a Sextuple System", Research Notes of the AAS, 10 (7): 208, doi:10.3847/2515-5172/ae8f36, ISSN 2515-5172.
  7. 1 2 3 Ammler-von Eiff, Matthias; Reiners, Ansgar (June 2012), "New measurements of rotation and differential rotation in A-F stars: are there two populations of differentially rotating stars?", Astronomy & Astrophysics, 542: A116, arXiv:1204.2459, Bibcode:2012A&A...542A.116A, doi:10.1051/0004-6361/201118724, S2CID 53666672.
  8. ↑ David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, arXiv:1501.03154, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146, S2CID 33401607.
  9. 1 2 Díaz, C. G.; et al. (July 2011), "Accurate stellar rotational velocities using the Fourier transform of the cross correlation maximum", Astronomy & Astrophysics, 531: A143, arXiv:1012.4858, Bibcode:2011A&A...531A.143D, doi:10.1051/0004-6361/201016386, S2CID 119286673.
  10. ↑ "HD 16754". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-12-16.
  11. ↑ Makarov, V. V.; Kaplan, G. H. (May 2005), "Statistical Constraints for Astrometric Binaries with Nonlinear Motion", The Astronomical Journal, 129 (5): 2420–2427, Bibcode:2005AJ....129.2420M, doi:10.1086/429590.
  12. ↑ Frankowski, A.; et al. (March 2007), "Proper-motion binaries in the Hipparcos catalogue. Comparison with radial velocity data", Astronomy and Astrophysics, 464 (1): 377–392, arXiv:astro-ph/0612449, Bibcode:2007A&A...464..377F, doi:10.1051/0004-6361:20065526, S2CID 14010423.
  13. ↑ Elliott, P.; et al. (May 2016), "Search for associations containing young stars (SACY). VII. New stellar and substellar candidate members in the young associations", Astronomy & Astrophysics, 590: 28, arXiv:1604.03550, Bibcode:2016A&A...590A..13E, doi:10.1051/0004-6361/201628253, S2CID 53138126, A13.
  14. ↑ Zuckerman, B.; et al. (May 2011), "The Tucana/Horologium, Columba, AB Doradus, and Argus Associations: New Members and Dusty Debris Disks", The Astrophysical Journal, 732 (2): 61, arXiv:1104.0284v1, Bibcode:2011ApJ...732...61Z, doi:10.1088/0004-637X/732/2/61, S2CID 62797470.
  15. ↑ Schröder, C.; Schmitt, J. H. M. M. (November 2007), "X-ray emission from A-type stars", Astronomy and Astrophysics, 475 (2): 677–684, Bibcode:2007A&A...475..677S, doi:10.1051/0004-6361:20077429.