Astronomy:Iota Arae
  | |
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Ara[1] |
| Right ascension | 17h 23m 16.07624s[2] |
| Declination | −47° 28′ 05.5057″[2] |
| Apparent magnitude (V) | 5.18–5.26[3] |
| Characteristics | |
| Spectral type | B2 IVe + sdO[4] |
| U−B color index | −0.82[5] |
| B−V color index | −0.11[5] |
| R−I color index | −0.08 |
| Variable type | BE[3] |
| Astrometry | |
| Radial velocity (Rv) | −19.0±7.4[6] km/s |
| Proper motion (μ) | RA: −6.209[2] mas/yr Dec.: −17.699[2] mas/yr |
| Parallax (π) | 3.5613 ± 0.0904[2] mas |
| Distance | 920 ± 20 ly (281 ± 7 pc) |
| Absolute magnitude (MV) | −2.06[1] |
| Orbit[4] | |
| Period (P) | 176.17±0.04 |
| Inclination (i) | 46±6° |
| Periastron epoch (T) | 2458654.2±0.5 HJD |
| Semi-amplitude (K1) (primary) | 5.80±0.06 km/s |
| Semi-amplitude (K2) (secondary) | 57.6±0.6 km/s |
| Details | |
| ι Ara A | |
| Mass | 8.3±0.4[7] M☉ |
| Radius | 6.3[2] R☉ |
| Luminosity | 10,864[8] L☉ |
| Surface gravity (log g) | 4.18[8] cgs |
| Temperature | 20,172[2] K |
| Rotational velocity (v sin i) | 340[8] km/s |
| Age | 30.0±7.4[7] Myr |
| ι Ara B | |
| Mass | 1.06±0.29[4] M☉ |
| Radius | 0.61±0.09[9] R☉ |
| Luminosity | 437[9] L☉ |
| Temperature | 33,800[9] K |
| Other designations | |
| Database references | |
| SIMBAD | data |
Iota Arae is a binary star system in the southern constellation of Ara. Its name is a Bayer designation that is Latinized from ι Arae, and abbreviated Iota Ara or ι Ara. The system has a combined apparent visual magnitude of 5.2. Based upon the Bortle Dark-Sky Scale, this means it is visible to the naked eye from suburban skies. Parallax measurements yield a distance estimate of 920 light-years (281 parsecs), give or take a 20 light-year margin of error. It is drifting closer to the Sun with a radial velocity of around −19 km/s.[6]
The primary component is an evolved subgiant star with a stellar classification of B2 IVe.[4] 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.[8] The Doppler effect from this rotation is causing the absorption lines to widen and become nebulous.
Iota Arae has around 8.3[7] times the mass of the Sun and is shining brightly with 10,864 times the Sun's luminosity.[8] This energy is being radiated into space from the outer atmosphere at an effective temperature of 20,172 K,[2] giving it the characteristic blue-white hue of a B-type star.[12] 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.[3] In a study of the Hipparcos data, it was found to vary in brightness by 0.054 in magnitude with no clear period.[13]
This is a spectroscopic binary system with an orbital period of 176 days. The companion is a subdwarf O star with a mass similar to the Sun but only 61% of the Sun's radius.[4]
References
- ↑ 1.0 1.1 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940 Gaia DR3 record for this source at VizieR.
- ↑ 3.0 3.1 3.2 Samus, N. N. et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S 1. Bibcode: 2009yCat....102025S.
- ↑ 4.0 4.1 4.2 4.3 4.4 Wang, Luqian et al. (April 2023). "The Orbital and Physical Properties of Five Southern Be+sdO Binary Systems" (in en). The Astronomical Journal 165 (5): 203. doi:10.3847/1538-3881/acc6ca. ISSN 1538-3881. Bibcode: 2023AJ....165..203W.
- ↑ 5.0 5.1 Kozok, J. R. (September 1985). "Photometric observations of emission B-stars in the southern Milky Way". Astronomy and Astrophysics Supplement Series 61: 387–405. Bibcode: 1985A&AS...61..387K.
- ↑ 6.0 6.1 Kharchenko, N. V. et al. (2007). "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ∼55000 stars and mean radial velocities of 516 Galactic open clusters and associations". Astronomische Nachrichten 328 (9): 889. doi:10.1002/asna.200710776. Bibcode: 2007AN....328..889K.
- ↑ 7.0 7.1 7.2 Tetzlaff, N. et al. (January 2011). "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun". Monthly Notices of the Royal Astronomical Society 410 (1): 190–200. doi:10.1111/j.1365-2966.2010.17434.x. Bibcode: 2011MNRAS.410..190T.
- ↑ 8.0 8.1 8.2 8.3 8.4 Zorec, J. et al. (November 2016). "Critical study of the distribution of rotational velocities of Be stars. I. Deconvolution methods, effects due to gravity darkening, macroturbulence, and binarity". Astronomy & Astrophysics 595: 26. doi:10.1051/0004-6361/201628760. Bibcode: 2016A&A...595A.132Z.
- ↑ 9.0 9.1 9.2 Wang, Luqian et al. (2021). "The Detection and Characterization of Be+sdO Binaries from HST/STIS FUV Spectroscopy". The Astronomical Journal 161 (5): 248. doi:10.3847/1538-3881/abf144. Bibcode: 2021AJ....161..248W.
- ↑ "iot Ara". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=iot+Ara.
- ↑ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html.
- ↑ "The Colour of Stars". Australia Telescope, Outreach and Education. Commonwealth Scientific and Industrial Research Organisation. December 21, 2004. http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html.
- ↑ Lefèvre, L. et al. (November 2009). "A systematic study of variability among OB-stars based on HIPPARCOS photometry". Astronomy and Astrophysics 507 (2): 11411201. doi:10.1051/0004-6361/200912304. Bibcode: 2009A&A...507.1141L.
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