HD 16754

This article is about s Eridani. For S Eridani, see 64 Eridani.

HD 16754 is a binary^[12] or triple-star^[9] 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.^[3] It is located at a distance of approximately 132 light years from the Sun based on parallax,^[2] and is drifting further away with a radial velocity of +18 km/s.^[3] The system is a member of the Columba association of co-moving stars.^[13]

HD 16754

Observation data Epoch J2000      Equinox J2000
Constellation	Eridanus[1]
Right ascension	02h 39m 47.96544s[2]
Declination	−42° 53′ 30.3638″[2]
Apparent magnitude (V)	+4.74[3]
Characteristics
Spectral type	A1 Vb[4] + M2-5V[5] + ?
B−V color index	0.061±0.003[3]
Astrometry
Radial velocity (Rv)	+18.0±4.2[3] km/s
Proper motion (μ)	RA: +88.20[6] mas/yr Dec.: −17.82[6] mas/yr
Parallax (π)	24.7076±0.3930 mas[2]
Distance	132 ± 2 ly (40.5 ± 0.6 pc)
Absolute magnitude (MV)	+1.76[7]
Details
Aa
Mass	1.95[8] M☉
Radius	1.93[9] R☉
Luminosity	17.44[3] L☉
Surface gravity (log g)	4.40±0.14[8] cgs
Temperature	9,099±309[8] K
Metallicity [Fe/H]	−0.06[4] dex
Rotational velocity (v sin i)	167.6±1.7[10] or 13.4±1.5[7] km/s
Age	212[8] or 30[9] Myr
Other designations
s Eri, CD−43°814, FK5 2185, HD 16754, HIP 12413, HR 789, SAO 215996[11]
Database references
SIMBAD	data

This object was flagged as an astrometric binary based on proper motion measurements made from the Hipparcos spacecraft.^[14][15] Zuckerman et al. (2011) consider it a multi-star system, with a bright A-type primary plus a faint M-type companion at an angular separation of 25″ to the north. The astrometric companion to the primary remains unresolved.^[9]

The main component is an A-type main-sequence star with a stellar classification of A1 Vb.^[4] Based upon stellar models, it has an age estimated at 212 million years.^[8] Consistency with its membership in the Columba association suggests a much younger age of 30 million years.^[9] Earlier measurements showed a high projected rotational velocity of 168 km/s.^[10] However, Ammler-von Eiff and Reiners (2012) found a much lower velocity of 13 km/s.^[7]

The visible companion is a red dwarf star with a class in the range M2-5V. The system is a source of X-ray emission with a luminosity of 924×10²⁰ W, which is most likely coming from this component and the unresolved companion.^[5]