18 Monocerotis

Star in the constellation Monoceros

18 Monocerotis
Observation data Epoch J2000 Equinox J2000
Location of 18 Monocerotis (circled red)
Constellation	Monoceros
Right ascension	06^h 47^m 51.64752^s^[1]
Declination	2° 24′ 43.7737″^[1]
Apparent magnitude (V)	4.47^[2]
Characteristics
Spectral type	K0+IIIaBa0.2^[3]
U−B color index	+1.04^[2]
B−V color index	+1.11^[2]
Astrometry

Radial velocity (R_v)	+11.29^[4] km/s
Proper motion (μ)	RA: -16.898^[1] mas/yr Dec.: -16.229^[1] mas/yr
Parallax (π)	8.0947 ± 0.2385 mas^[1]
Distance	400 ± 10 ly (124 ± 4 pc)
Absolute magnitude (M_V)	-0.78^[5]

Orbit^[6]^[7]
Primary	18 Monocerotis A
Companion	18 Monocerotis B
Period (P)	1760.9±1.9 d
Semi-major axis (a)	6.63 mas
Eccentricity (e)	0.40±0.04
Inclination (i)	96.25°
Longitude of the node (Ω)	47.63°
Periastron epoch (T)	2441942.5
Argument of periastron (ω) (secondary)	172±6°
Details
18 Mon A
Radius	26.95+1.56 −0.81^[1] `R`_☉
Luminosity	311.2±10.5^[1] `L`_☉
Surface gravity (log g)	2.59^[8] cgs
Temperature	4,750^[9] K
Metallicity [Fe/H]	-0.03^[5] dex
Rotational velocity (v sin i)	< 2.0^[10] km/s

Other designations
18 Mon, BD+02°1397, FK5 258, GC 8892, HD 49293, HIP 32578, HR 2506, SAO 114428^[11]
Database references
SIMBAD	data

18 Monocerotis is a binary star system located about half way from Orion's Belt to Procyon,^[6] in the equatorial constellation of Monoceros.^[11] It is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of 4.47,^[2] and is positioned around 370^[1] light years away from the Sun based on parallax. The system is receding from the Earth with a heliocentric radial velocity of +11 km/s.^[4]

It is reported as a single-lined spectroscopic binary with an orbital period of 1,760.9 days (4.8 years) and an eccentricity of 0.4.^[6] The visible component is an aging K-type giant star with a stellar classification of K0+IIIaBa0.2,^[3] showing a slight overabundance of barium. The spectrum displays strong violet lines of CN.^[6] With the supply of hydrogen at its core exhausted, this star has expanded to 27^[1] times the radius of the Sun. It is radiating 311^[1] times the luminosity of the Sun from its swollen photosphere at an effective temperature of 4,750 K.^[9]

References

^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
^ ^a ^b ^c ^d Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D.
^ ^a ^b Hoffleit, D.; Warren, W. H. (1995). "VizieR Online Data Catalog: Bright Star Catalogue, 5th Revised Ed. (Hoffleit+, 1991)". VizieR On-line Data Catalog: V/50. Originally Published in: 1964BS....C......0H. 5050. Bibcode:1995yCat.5050....0H.
^ ^a ^b Famaey, B.; Jorissen, A.; Luri, X.; Mayor, M.; Udry, S.; Dejonghe, H.; Turon, C. (2005). "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data". Astronomy & Astrophysics. 430: 165–186. arXiv:astro-ph/0409579. Bibcode:2005A&A...430..165F. doi:10.1051/0004-6361:20041272. S2CID 17804304.
^ ^a ^b Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644. Vizier catalog entry
^ ^a ^b ^c ^d Griffin, R. F. (1984). "Spectroscopic binary orbits from photoelectric radial velocities. Paper 59: 18 Monocerotis". The Observatory. 104: 267. Bibcode:1984Obs...104..267G.
^ ESA (1997). "The Hipparcos and Tycho Catalogues". VizieR On-line Data Catalog. Bibcode:1997yCat.1239....0E.
^ Soubiran, Caroline; Le Campion, Jean-François; Brouillet, Nathalie; Chemin, Laurent (2016). "The PASTEL catalogue: 2016 version". Astronomy & Astrophysics. 591: A118. arXiv:1605.07384. Bibcode:2016A&A...591A.118S. doi:10.1051/0004-6361/201628497. S2CID 119258214.
^ ^a ^b Gontcharov, G. A. (2009). "Red giant clump in the Tycho-2 catalogue". Astronomy Letters. 34 (11): 785–796. arXiv:1607.00619. Bibcode:2008AstL...34..785G. doi:10.1134/S1063773708110078. S2CID 73524157. Vizier catalog entry
^ De Medeiros, J. R.; Mayor, M. (1999). "A catalog of rotational and radial velocities for evolved stars". Astronomy and Astrophysics Supplement Series. 139 (3): 433. arXiv:astro-ph/0608248. Bibcode:1999A&AS..139..433D. doi:10.1051/aas:1999401. Vizier catalog entry
^ ^a ^b "18 Mon". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-05-30.

Constellation of Monoceros

Stars

Bayer	α β γ δ ε ζ
Flamsteed	1 2 3 6 7 9 10 12 13 14 16 17 18 19 20 21 23 24 25 27 28 77 Ori 78 Ori
Variable	R S (15) T U V RU RW SV TU UX VV VY AO AR AU AX BE BN BT BX CL CS CV CW DD FU GI IM PZ V372 V396 V474 V505 V569 V577 V578 V582 V588 V589 V590 V592 V614 V616 V638 V640 V641 V644 V653 V682 V684 V689 V694 V695 V696 V700 V715 V721 V723 V728 V731 V739 V743 V750 V753 V827 V838 V926
HR	2150 2154 2179 2205 2224 2234 2237 2267 2270 2280 2292 2300 2313 2317 2321 2324 2325 2328 2333 2342 2347 2355 2367 2370 2375 2378 2381 2386 2395 2406 2409 2418 2426 2430 2440 2458 2461 2467 2469 2474 2479 2502 2508 2514 2521 2530 2543 2551 2555 2570 2572 2577 2582 2584 2589 2599 2606 2610 2613 2624 2627 2636 2639 2647 2655 2656 2663 2676 2694 2731 2732 2739 2752 2765 2806 2807 2811 2833 2865 2866 2867 2876 2883 2920 2958 3014 3047 3054 3072 3150 3172 3174 3189
HD	42132 44179 44219 45090 45166 45215 45652 (Lusitânia) 46149 46150 46202 46223 46375 46966 48099 50064 50138 50281 52265 (Citalá) 65938 66428
Other	A0620-00 AFGL 961 CoRoT-1 CoRoT-4 CoRoT-5 CoRoT-7 CoRoT-12 CoRoT-13 CoRoT-14 CoRoT-15 CoRoT-18 CoRoT-19 CoRoT-20 CoRoT-21 CoRoT-24 Gliese 282 Monoceros R2 IRS 3 NGC 2264 IRS 1 Ross 614 Scholz's SCR 0640−0552 UGPS J0652+0324 UGPS J0722−0540

Exoplanets	CoRoT-1b CoRoT-4b CoRoT-5b CoRoT-7b CoRoT-7c CoRoT-7d CoRoT-12b CoRoT-13b CoRoT-14b CoRoT-15b CoRoT-18b CoRoT-19b CoRoT-20b CoRoT-20c CoRoT-21b CoRoT-24b CoRoT-24c HD 44219 b HD 45652 b (Viriato) HD 46375 b HD 52265 b (Cayahuanca)