Iota Arae

ι Arae
Location of ι Arae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Ara
Right ascension 17h 23m 16.07624s[1]
Declination −47° 28′ 05.5057″[1]
Apparent magnitude (V) 5.18 - 5.26[2]
Characteristics
Spectral type B2 IIIne[3]
U−B color index −0.82[4]
B−V color index −0.11[4]
R−I color index −0.08
Variable type BE[2]
Astrometry
Radial velocity (Rv)−19[5] km/s
Proper motion (μ) RA: −6.209[1] mas/yr
Dec.: −17.699[1] mas/yr
Parallax (π)3.5613 ± 0.0904 mas[1]
Distance920 ± 20 ly
(281 ± 7 pc)
Absolute magnitude (MV)−2.06[6]
Details
Mass8.3±0.4[7] M☉
Radius6.3[1] R☉
Luminosity10,864[8] L☉
Surface gravity (log g)4.18[8] cgs
Temperature20,172[1] K
Rotational velocity (v sin i)340[8] km/s
Age30.0±7.4[7] Myr
Other designations
ι Ara, CD−47°11484, FK5 3379, HD 157042, HIP 85079, HR 6451, NSV 8566, SAO 227886.[9]
Database references
SIMBADdata

Iota Arae, Latinized from ι Arae, is the Bayer designation for a star in the southern constellation of Ara. It is 920 light-years (281 parsecs) from Earth, give or take a 20 light-year margin of error, and has an apparent visual magnitude of 5.2. Based upon the Bortle Dark-Sky Scale, this means the star is visible to the naked eye from suburban skies.

This is an evolved giant star with a stellar classification of B2 IIIne.[3] The 'e' notation indicates the spectrum displays emission lines, which means this is a Be star that is surrounded by hot, circumstellar gas. It is spinning rapidly with a projected rotational velocity of 340 km/s. The Doppler effect from this rotation is causing the absorption lines to widen and become nebulous, as indicated by the 'n' notation in the stellar class.

A light curve for Iota Arae, plotted from TESS data[10]

Iota Arae has around 8.3 times the mass of the Sun and is shining brightly with 10,864 times the Sun's luminosity. This energy is being radiated into space from the outer atmosphere at an effective temperature of 20,172 K, giving it the characteristic blue-white hue of a B-type star.[11] The General Catalog of Variable Stars classifies it as a BE variable star, ranging from visual magnitude 5.18 to 5.26 with a period of 13.36 hours.[2] In a study of the Hipparcos data, it was found to vary in brightness by 0.054 in magnitude with no clear period.[12]

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  3. ^ a b Cite error: The named reference apj157_313 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference aass61_387 was invoked but never defined (see the help page).
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  7. ^ a b Cite error: The named reference mnras410_1_190 was invoked but never defined (see the help page).
  8. ^ a b c Cite error: The named reference zorec2016 was invoked but never defined (see the help page).
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  10. ^ Cite error: The named reference MAST was invoked but never defined (see the help page).
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  12. ^ Cite error: The named reference aaa507_2_11411201 was invoked but never defined (see the help page).