CX Draconis

CX Draconis

Light curves for CX Draconis. The main plot, from Hipparcos data, [1] shows the long-term variability. The inset plot, from TESS data, [2] shows how the brightness changes of short timescales.
Observation data Epoch J2000.0        Equinox J2000.0
Constellation	Draco
Right ascension	18h 46m 43.089s [3]
Declination	+52° 59′ 16.65″ [3]
Apparent magnitude  (V)	5.68 to 5.99 [4]
Characteristics
Spectral type	B2.5 V + F5 III [5]
Variable type	γ Cas + rotating ellipsoidal [4]
Astrometry
Radial velocity (Rv)	−2.1±2.3 [6]  km/s
Proper motion (μ)	RA: 10.965  mas/yr [3] Dec.: −4.920  mas/yr [3]
Parallax (π)	2.8262 ± 0.0587  mas [3]
Distance	1,150 ± 20  ly (354 ± 7  pc)
Orbit [7]
Period (P)	6.695957±0.000043 d
Semi-major axis (a)	≥ 3.253 Gm [8]
Eccentricity (e)	0.052±0.006
Inclination (i)	52 to 55°
Periastron epoch (T)	2,442,549.48±0.24  HJD
Argument of periastron (ω) (secondary)	267.9±6.4°
Semi-amplitude (K1) (primary)	33.66±0.86 km/s
Semi-amplitude (K2) (secondary)	145.92±0.82 km/s
Details
Primary
Mass	7.3 [9]   M☉
Surface gravity (log g)	3.71±0.27 [10]   cgs
Temperature	19,580±640 [10]   K
Rotational velocity (v sin i)	163±10 [10]  km/s
Secondary
Mass	~1.7 [9]   M☉
Temperature	6,500 [11]   K
Rotational velocity (v sin i)	~65 [11]  km/s
Other designations
CX Dra, BD+52°2280, FK5  1492, GC  25757, HD  174237, HIP  92133, HR  7084, SAO  31165 [12]
Database references
SIMBAD	data

CX Draconis is an interacting binary star system in the northern constellation of Draco, abbreviated CX Dra. It has the designation HD 174237 in the Henry Draper Catalogue ; CX Draconis is the variable star designation. This is a double-lined spectroscopic binary system with a near circular orbit. ^[7] The brightness of the system undergoes long-term irregular fluctuations, ^[11] ranging from an apparent visual magnitude of 5.68 down to 5.99. ^[4] Based on parallax measurements, it is located at a distance of approximately 1,150  light years from the Sun. ^[3]

In 1921, this target was found to have a varying radial velocity by J. S. Plaskett and associates. ^{[13] [14]} It was shown to be a Be star by O. C. Mohler in 1940, ^[15] and in 1965 M. Lacoarret studied variations in the hydrogen alpha emission profiles from the target. This system was discovered to be a photometric variable by P. Merlin in 1975. ^[14] P. Koubský measured the radial velocity variations in 1976, ^[16] and in 1978 published orbital elements for this binary system with a period of 6.696 days. ^[17] He found that the variation in emission lines matched the time scale of the orbit, indicating that this is an interacting binary. ^[11]

Using observations from the Einstein Observatory, in 1984 this system was shown to be an X-ray source by E. F. Guinan and associates. This emission may be coming from the cooler secondary that is phase-locked with the primary and is magnetically active due to rapid rotation. ^[18] In 1992, J. Horn and associates determined that the secondary component is an evolved F-type giant star. Evidence suggests this star is overflowing its Roche lobe with gas streaming toward the primary. ^[11]

Models indicate that the main source of the H-alpha emission is located mid-way between the two stars, with other emission lines originating from an accretion disk orbiting the primary. The circumstellar environment is changing in cycles lasting hundreds of days. ^[7] Infrared emission to the northeast of the system suggests it may be undergoing systematic mass loss. ^[19]

References

1. EAS (1997), "The HIPPARCOS and TYCHO catalogues", Astrometric and Photometric Star Catalogues Derived from the ESA Hipparcos Space Astrometry Mission, ESA SP Series, 1200, Noordwijk, Netherlands: ESA Publications Division, Bibcode:1997ESASP1200.....E, ISBN   9290923997 , retrieved 15 October 2022.
2. MAST: Barbara A. Mikulski Archive for Space Telescopes, Space Telescope Science Institute, retrieved 8 December 2021.
3. Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics . 649: A1. arXiv: 2012.01533 . Bibcode:2021A&A...649A...1G. doi: 10.1051/0004-6361/202039657 . S2CID   227254300. (Erratum:  doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
4. Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports , 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID   125853869.
5. Berdyugin, A.; Piirola, V. (October 2002), "Polarization variability in the interacting Be binary CX Draconis", Astronomy and Astrophysics, 394: 181–186, Bibcode:2002A&A...394..181B, doi: 10.1051/0004-6361:20021109 .
6. Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35495 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.
7. Richards, Mercedes T.; Koubský, Pavel; Šimon, Vojtěch; Peters, Geraldine J.; Hirata, Ryuko; Škoda, Petr; Masuda, Seiji (March 2000), "A Multiwavelength Study of Spectral Variations in the CX Draconis Binary", The Astrophysical Journal, 531 (2): 1003–1027, Bibcode:2000ApJ...531.1003R, doi: 10.1086/308491 , S2CID   122795224.
8. Abt, Helmut A.; Gomez, Ana E.; Levy, Saul G. (October 1990), "The Frequency and Formation Mechanism of B2--B5 Main-Sequence Binaries", Astrophysical Journal Supplement, 74: 551, Bibcode:1990ApJS...74..551A, doi:10.1086/191508.
9. Harmanec, P.; Koubský, P.; Nemravová, J.; Royer, F.; Briot, D.; North, P.; Lampens, P.; Frémat, Y.; Yang, S.; Božić, H.; Kotková, L.; Škoda, P.; Šlechta, M.; Korčáková, D.; Wolf, M.; Zasche, P. (January 2015), "Properties and nature of Be stars 30. Reliable physical properties of a semi-detached B9.5e+G8III binary BR CMi = HD 61273 compared to those of other well studied semi-detached emission-line binaries", Astronomy and Astrophysics, 573, arXiv: 1411.5651 , Bibcode:2015A&A...573A.107H, doi:10.1051/0004-6361/201424640, S2CID   118456434, A107.
10. 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" (PDF), Astronomy & Astrophysics, 595: 26, Bibcode:2016A&A...595A.132Z, doi: 10.1051/0004-6361/201628760 .
11. Horn, J.; Hubert, A. M.; Hubert, H.; Koubsky, P.; Bailloux, N. (June 1992), "CX Draconis : the orbit parameters for both components", Astronomy and Astrophysics, 259: L5 –L8, Bibcode:1992A&A...259L...5H.
12. "CX Dra". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 14 February 2023.
13. Plaskett, J. S.; Harper, W. E.; Young, R. K.; Plaskett, H. H. (1921), "Eighty-eight spectroscopic binaries", Publications of the Dominion Astrophysical Observatory Victoria, 1: 287–306, Bibcode:1921PDAO....1..287P.
14. Merlin, P. (February 1975), "Variations photométriques de l'étoile B à émission HD 174237", Astronomy and Astrophysics (in French), 39: 139–141, Bibcode:1975A&A....39..139M.
15. Mohler, Orren C. (September 1940), "Six New BE Stars", Astrophysical Journal, 92: 315, Bibcode:1940ApJ....92..315M, doi: 10.1086/144221 .
16. Koubský, P. (October 1976), "HD 174237 (MWC 608)", Information Bulletin on Variable Stars, 1188 (1): 1, Bibcode:1976IBVS.1188....1K.
17. Koubský, P. (1978), "Properties and Nature of Be and Shell Stars. 9. Periodic Radial-velocity Changes of HD 174237", Bulletin of the Astronomical Institute of Czechoslovakia, 29: 288, Bibcode:1978BAICz..29..288K.
18. Guinan, E. F.; Koch, R. H.; Plavec, M. J. (July 1984), "Einstein observations of selected close binaries and shell stars", Astrophysical Journal, 282: 667–674, Bibcode:1984ApJ...282..667G, doi:10.1086/162246.
19. Mayer, A.; Deschamps, R.; Jorissen, A. (March 2016), "Search for systemic mass loss in Algols with bow shocks", Astronomy & Astrophysics, 587: A30, arXiv: 1601.00218 , Bibcode:2016A&A...587A..30M, doi:10.1051/0004-6361/201526623, S2CID   54596624, A30.

Further reading

• Pustylnik, I.; Kalv, P.; Harvig, V.; Aas, T. (2007), "On Quasi-Periodic Intrinsic Light Variability in a Close Spectroscopic Binary CX DRA", Odessa Astronomical Publications, 20: 186, Bibcode:2007OAP....20..186P.
• Berdyugin, A.; Piirola, V. (October 2002), "Polarization variability in the interacting Be binary CX Draconis", Astronomy and Astrophysics, 394: 181–186, Bibcode:2002A&A...394..181B, doi: 10.1051/0004-6361:20021109 .
• Skoda, Petr; Koubsky, Pavel (2000), Smith, M. A.; Henrichs, H. F.; Fabregat, J. (eds.), "IUE Spectra of Be Star CX Dra: Evidence for Winds" (PDF), The Be Phenomenon in Early-Type Stars, IAU Colloquium 175, ASP Conference Series, vol. 214, p. 573, Bibcode:2000ASPC..214..573S , retrieved 15 February 2023.
• Iwamatsu, H.; Hirata, R.; Masuda, S. (2000), Smith, Myron A.; Henrichs, Huib F. (eds.), "Origin of Circumstellar Matter in the Spectroscopic Binary CX Dra", The Be Phenomenon in Early-Type Stars, IAU Colloquium 175, ASP Conference Proceedings, vol. 214, Astronomical Society of the Pacific, p. 701, Bibcode:2000ASPC..214..701I, ISBN   1-58381-045-5.
• Koubský, P.; Richards, M. T.; Šimon, V. (February 1998), Dusek, J.; Zejda, M. (eds.), "Circumstellar Matter in the Interacting Binary CX Draconis", Proceedings of the 29th Conference on Variable Star Research. 7th - 9th November 1997. Brno, Czech Republic, p. 64, Bibcode:1998stel.conf...64K, ISBN   80-85882-09-4.
• Koubsky, P.; Harmanec, P.; Bozic, H.; Rercy, J. R.; Ziznovsky, J.; Huang, L.; Richards, M. T.; Hadrava, P.; Simon, V. (1998), "Spectroscopy and Photometry of the Interacting Binary CX Draconis - Evidence for Circumstellar Mater", Hvar Observatory Bulletin, 22 (1): 17–36, Bibcode:1998HvaOB..22...17K.
• Simon, V. (April 1996), "The interacting binary CX Draconis: new orbital elements and evidence for mass transfer.", Astronomy and Astrophysics, 308: 799–808, Bibcode:1996A&A...308..799S.
• Koubský, P.; Horn, J.; Harmanec, P.; Peters, G. J.; Polidan, R. S. (1990), İbanoğlu, C (ed.), "Interacting Binary CX Draconis", Active Close Binaries, NATO ASI Series, vol. 319, Dordrecht: Springer, pp. 237–238, doi:10.1007/978-94-009-0679-2_18, ISBN   978-94-010-6790-4.
• Magalashvili, N. L.; Kumsishvili, Ya. I. (1986), "Photometric observations of the emission B star CX Dra (HD 174237)", Byulleten Abastumanskaya Astrofizicheskaya Observatoriya, 61: 79–82, Bibcode:1986AbaOB..61...79M.
• Harmanec, P.; Horn, J.; Koubsky, P.; Ziznovsky, J. (March 1981), "Call for Systematic Photoelectric Observations of CX Dra", Information Bulletin on Variable Stars, 1931: 1, Bibcode:1981IBVS.1931....1H.
• Koubský, P.; Harmanec, P.; Horn, J.; Jerzykiewicz, M.; Papoušek, J.; Kříž, S.; Pavlovski, K.; Ždárský, F. (1980), "Properties and Nature of Be and Shell Stars. 10. Light and Colour Variations of CX Dra", Bulletin of the Astronomical Institute of Czechoslovakia, 31 (2): 75–84, Bibcode:1980BAICz..31...75K.
• Koubský, P.; Harmanec, P.; Horn, J.; Jerzykiewicz, M.; Kríz, S.; Pavlovski, K.; Zdárský, F. (1980), "UBV photometry of CX Cra. Search for rapid variations" (PDF), Acta Universitatis Carolinae, Mathematica et Physica, 21 (2): 33–54, Bibcode:1980AcMPh..21...33K , retrieved 15 February 2023.