Upsilon4 Eridani

For other star systems with this Bayer designation, see Upsilon Eridani.

Upsilon⁴ Eridani is a close binary star system in the constellation Eridanus. It is visible to the naked eye with an apparent visual magnitude of 3.56.^[2] Based upon parallax measurements, the pair are located around 54.6 parsecs (178 ly) from the Sun.^[1]

Upsilon⁴ Eridani

Location of Upsilon4 in Eridanus (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Eridanus
Right ascension	04h 17m 53.66241s[1]
Declination	−33° 47′ 54.0569″[1]
Apparent magnitude (V)	3.56[2]
Characteristics
Spectral type	B8V + B9.5V[3]
U−B color index	−0.36[2]
B−V color index	−0.12[2]
Astrometry
Radial velocity (Rv)	+17.6[4] km/s
Proper motion (μ)	RA: +62.52[1] mas/yr Dec.: −7.24[1] mas/yr
Parallax (π)	18.33 ± 0.15 mas[1]
Distance	178 ± 1 ly (54.6 ± 0.4 pc)
Absolute magnitude (MV)	−0.20[5]
Orbit[6]
Period (P)	5.0103250±0.0000008 d
Semi-major axis (a)	1.902±0.006 mas
Eccentricity (e)	0
Inclination (i)	146.2±0.1°
Periastron epoch (T)	2454407.7214 ± 0.002 JD
Semi-amplitude (K1) (primary)	62.68±0.17[7] km/s
Semi-amplitude (K2) (secondary)	64.70±0.15[7] km/s
Details[6]
υ4 Eri A
Mass	3.17±0.07 M☉
Radius	2.32±0.18 R☉
Luminosity	100.6±4.3 L☉
Surface gravity (log g)	4.21±0.07 cgs
Temperature	12,930±440[8] K
Rotational velocity (v sin i)	19[8] km/s
Age	146[8] Myr
υ4 Eri B
Mass	3.07±0.07 M☉
Radius	2.32±0.18 R☉
Luminosity	87.4±3.3 L☉
Surface gravity (log g)	4.21±0.07 cgs
Temperature	12,250 K
Other designations
υ4 Eri, 41 Eridani, CD−34° 1614, HD 27376, HIP 20042, HR 1347, SAO 194902.[9]
Database references
SIMBAD	data

This is a double-lined spectroscopic binary star system,^[10] which means that the Doppler-shifted spectral lines of both components can be distinguished. The pair have a circular orbit with a period of five days. The system is composed of two B-type main-sequence stars: one has a stellar classification of B8V and the other B9.5V.^[3] Both stars show HgMn peculiarities in their spectrum,^[7] and their properties are nearly identical.^[6] The spin rate of the two stars is synchronized to their orbital period.^[6] It is possible that a nearby K-type star is also related.^[3]

References

1. van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
2. Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M.
3. Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
4. Evans, D. S. (June 20–24, 1966), Batten, Alan Henry; Heard, John Frederick (eds.), "The Revision of the General Catalogue of Radial Velocities", Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, vol. 30, University of Toronto: International Astronomical Union, p. 57, Bibcode:1967IAUS...30...57E.
5. Hubrig, S.; et al. (June 2001), "Search for low-mass PMS companions around X-ray selected late B stars", Astronomy and Astrophysics, 372: 152–164, arXiv:astro-ph/0103201, Bibcode:2001A&A...372..152H, doi:10.1051/0004-6361:20010452, S2CID 17507782.
6. Hummel, Christian A.; Schöller, Markus; Duvert, Gilles; Le Bouquin, Jean-Baptiste; Hubrig, Swetlana (2016), "The orbit of the mercury-manganese binary 41 Eridani", in Malbet, Fabien; Creech-Eakman, Michelle J.; Tuthill, Peter G. (eds.), Optical and Infrared Interferometry and Imaging V, Proceedings of SPIE, vol. 9907, pp. 99070Q, arXiv:1703.07668, Bibcode:2016SPIE.9907E..0QH, doi:10.1117/12.2231859, S2CID 125160002
7. Hubrig, S.; et al. (November 2012), "Magnetic fields of HgMn stars", Astronomy & Astrophysics, 547: 24, arXiv:1208.2910, Bibcode:2012A&A...547A..90H, doi:10.1051/0004-6361/201219778, S2CID 85520917, A90.
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. "* ups04 Eri -- Spectroscopic binary". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-10-13.{{cite web}}: CS1 maint: postscript (link)
10. Chini, R.; et al. (2012), "A spectroscopic survey on the multiplicity of high-mass stars", Monthly Notices of the Royal Astronomical Society, 424 (3): 1925, arXiv:1205.5238, Bibcode:2012MNRAS.424.1925C, doi:10.1111/j.1365-2966.2012.21317.x, S2CID 119120749.