W Orionis

W Orionis
	; The visual band light curve for W Orionis, plotted from ASAS data
Observation data; Epoch J2000 Equinox J2000
Constellation	Orion
Right ascension	05h 05m 23.72142s
Declination	+01° 10′ 39.4512″
Apparent magnitude (V)	4.4 - 6.9
Characteristics
Evolutionary stage	AGB
Spectral type	C-N5 C25.5 (C5,4(N5))
U−B color index	+6.84
B−V color index	+3.42
Variable type	SRb
Astrometry
Radial velocity (Rv)	+16.50 km/s
Proper motion (μ)	RA: +7.5 mas/yr ; Dec.: -1.4 mas/yr
Parallax (π)	2.65 ± 0.95 mas
Distance	approx. 1,200 ly ; (approx. 400 pc)
Absolute magnitude (MV)	−5.76
Details
Mass	1-2 M☉
Radius	406 R☉
Luminosity	6,761 L☉
Surface gravity (log g)	−0.60 cgs
Temperature	2,600 K
Metallicity [Fe/H]	0.0 dex
Other designations
	W Ori, BD−00°939, HD 32736, HIP 23680
Database references
SIMBAD	data

W Orionis is a carbon star in the constellation Orion, approximately 400 parsecs (1,300 ly) away. It varies regularly in brightness between extremes of magnitude 4.4 and 6.9 roughly every 7 months.

Variability

W Orionis is a semiregular variable with an approximately 212‑day cycle.^[5] A long secondary period of 2,450 days has also been reported.^[10]

Properties

The angular diameter of W Orionis has been measured using interferometry and a value of 9.7 mas is found. Although it is known to be a pulsating variable star, no changes in the diameter were seen.^[9]

Technetium has not been detected in W Orionis, an unexpected result since this s-process element should be dredged up in all thermally-pulsating AGB stars and especially in carbon stars.^[9]

References

^ "ASAS All Star Catalogue". The All Sky Automated Survey. Retrieved 8 December 2021.
^ ^a ^b ^c ^d ^e Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
^ Watson, C. L; Henden, A. A; Price, A (2006). "The International Variable Star Index (VSX)". The Society for Astronomical Sciences 25th Annual Symposium on Telescope Science. Held May 23–25. 25: 47. Bibcode:2006SASS...25...47W.
^ Barnbaum, Cecilia; Stone, Remington P. S; Keenan, Philip C (1996). "A Moderate-Resolution Spectral Atlas of Carbon Stars: R, J, N, CH, and Barium Stars". Astrophysical Journal Supplement. 105: 419. Bibcode:1996ApJS..105..419B. doi:10.1086/192323.
^ ^a ^b ^c Samus, N. N.; Durlevich, O. V.; 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.
^ ^a ^b 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.
^ Gontcharov, G. A (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. S2CID 119231169.
^ Guandalini, R; Cristallo, S (2013). "Luminosities of carbon-rich asymptotic giant branch stars in the Milky Way". Astronomy & Astrophysics. 555: A120. arXiv:1305.4203. Bibcode:2013A&A...555A.120G. doi:10.1051/0004-6361/201321225. S2CID 54918450.
^ ^a ^b ^c ^d ^e ^f ^g ^h Cruzalèbes, P; Jorissen, A; Rabbia, Y; Sacuto, S; Chiavassa, A; Pasquato, E; Plez, B; Eriksson, K; Spang, A; Chesneau, O (2013). "Fundamental parameters of 16 late-type stars derived from their angular diameter measured with VLTI/AMBER". Monthly Notices of the Royal Astronomical Society. 434 (1): 437–450. arXiv:1306.3288. Bibcode:2013MNRAS.434..437C. doi:10.1093/mnras/stt1037. S2CID 49573767.
^ Olivier, E. A; Wood, P. R (2003). "On the Origin of Long Secondary Periods in Semiregular Variables". The Astrophysical Journal. 584 (2): 1035. Bibcode:2003ApJ...584.1035O. doi:10.1086/345715.