Iota Trianguli

Iota Trianguli, also named Triminus,^[12] is a quadruple^[2] star system in constellation of Triangulum. The pair have a combined apparent magnitude of 4.95^[13] and are approximately 290 light-years from Earth.

A light curve for Iota Trianguli, plotted from Hipparcos data^[14]

Iota Trianguli

Location of ι Trianguli (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Triangulum
A
Right ascension	02h 12m 22.2797s[1]
Declination	+30° 18′ 11.053″[1]
Apparent magnitude (V)	5.32[2]
B
Right ascension	02h 12m 22.5637s[3]
Declination	+30° 18′ 12.342″[3]
Apparent magnitude (V)	6.83[2]
Characteristics
A
Spectral type	G0 III + G5 III[4]
B−V color index	+0.856[5]
Variable type	ellipsoidal + RS CVn[6]
B
Spectral type	F5V + ?[2]
B−V color index	+0.515[5]
Astrometry
A
Proper motion (μ)	RA: −64.350[1] mas/yr Dec.: −59.503[1] mas/yr
Parallax (π)	11.3011±0.1024 mas[1]
Distance	289 ± 3 ly (88.5 ± 0.8 pc)
B
Proper motion (μ)	RA: −64.414[3] mas/yr Dec.: −49.913[3] mas/yr
Parallax (π)	12.7375±0.5496 mas[3]
Distance	260 ± 10 ly (79 ± 3 pc)
Absolute magnitude (MV)	+0.20[7]
Orbit[8]
Primary	Aa
Companion	Ab
Period (P)	14.73018 days
Semi-major axis (a)	0.002[9]″
Eccentricity (e)	0.0035
Inclination (i)	55 – 58[9]°
Semi-amplitude (K1) (primary)	54.84 km/s
Semi-amplitude (K2) (secondary)	56.39 km/s
Orbit[10]
Primary	Ba
Companion	Bb
Period (P)	2.2365 days
Eccentricity (e)	0
Semi-amplitude (K1) (primary)	95.4 km/s
Semi-amplitude (K2) (secondary)	101.0 km/s
Details
Aa
Mass	2.50[9] M☉
Radius	4.0[8] R☉
Luminosity	61.7[8] L☉
Temperature	4,932[8] K
Rotational velocity (v sin i)	32.9[8] km/s
Ab
Mass	2.43[9] M☉
Radius	1.5[8] R☉
Luminosity	10.0[8] L☉
Temperature	6,486[8] K
Rotational velocity (v sin i)	3.0[8] km/s
Ba
Mass	1.58[9] M☉
Bb
Mass	1.56[9] M☉
Other designations
Triminus, ι Tri, 6 Tri, TZ Tri, BD+29°371, HD 13480, HIP 10280, HR 642, SAO 55347, WDS J02124+3018[11]
Database references
SIMBAD	data

Both components of ι Trianguli are spectroscopic binaries and the brighter pair is variable. It was discovered to be a variable star in 1980, by Douglas S. Hall et al.^[15] It has been given the variable star designation TZ Trianguli. The variations are due to the ellipsoidal shape of the stars as they rotate, and also it is classified as an RS Canum Venaticorum variable.^[16]

Nomenclature

Iota Trianguli, Latinized from ι Trianguli, is the star's Bayer designation; it is also known by the Flamsteed designation 6 Trianguli. Together with 10 Trianguli and 12 Trianguli, it formed part of the obsolete constellation Triangulum Minus.

The Latin name "Triminus" is composed of the IAU abbrevation of "Tri" for Triangulum and "Minus" for Triangulum Minus, or the lesser triangle made by Johannes Hevelius. The IAU Working Group on Star Names approved the name Triminus for this star on 25 August 2025 and it is now so entered in the IAU Catalog of Star Names.^[12]