View source for Astronomy:VW Cephei

{{Short description|Star system in the constellation Cepheus}}

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{{Starbox begin 
| name = VW Cephei
}}
{{Starbox image
| image = [[Image:VWCepLightCurve.png|250px]]
| caption = A [[Astronomy:Photometric system#Photometric letters|visual band]] [[Astronomy:Light curve|light curve]] for VW Cephei, adapted from Kreiner and Winiarski (1981)<ref name="Kreiner"/>
}}
{{Starbox observe 
| epoch = [[Astronomy:J2000.0|J2000.0]]
| constell = [[Astronomy:Cepheus (constellation)|Cepheus]]
| ra={{RA|20|37|21.5449}}
| dec={{DEC|+75|36|01.456}}
| appmag_v = 7.38
}} 
{{Starbox character 
| class = G5V/G8V/?K3V/?M5V
}} 
{{Starbox astrometry 
| dist_ly = 90.95
| dist_pc = 27.9<ref name="Zasche & Wolf" />
}} 
{{Starbox detail 
| mass = 1.21/0.22/0.75/0.19?
| radius = 0.9/0.55/0.77/0.23?
| luminosity = 0.66/0.17/0.26/0.0038?
| temperature = ≈5500/5000/≈4700/≈3000
}} 
{{Starbox orbit
| period = 0.0007625
| axis = 0.0083[[Astronomy:Astronomical unit|AU]]s
| eccentricity = 0 (fixed)
}} 
{{Starbox catalog 
| names = [[Astronomy:Variable star designation|VW]] Cep, LHS 3565, SAO 9828, LTT 16039, BD+75 752, GJ 9703, HD 197433, HIP 101750.  
}}
{{Starbox reference
| Simbad = VW+Cep
}}
{{Starbox end}}

'''VW Cephei''' ('''VW Cep''') is an eclipsing [[Astronomy:Contact binary|contact binary]] of [[Astronomy:W Ursae Majoris|W Ursae Majoris]]-type located roughly at 90.6 light years from the [[Astronomy:Sun|Sun]], whose two component stars share a common outer layer. Because the two components share their outer layers, as the components of [[Astronomy:W Ursae Majoris|W Ursae Majoris]] do, they have the same [[Astronomy:Stellar classification|stellar classification]], and are classified as yellow G-type [[Astronomy:Main sequence|main sequence]] dwarfs. The components take 0.2783 days (roughly 6.7 hours) to revolve around a common barycentre. Orbital period variations suggest the presence of one more additional perturbing objects of likely low-mass [[Astronomy:Star|stellar]] nature.

==Unseen companion(s)==

Orbital period variations suggest the presence of one more perturbing unseen object around the eclipsing binary.<ref name="Zasche & Wolf">{{cite journal | arxiv=0711.3980| author=Zasche| name-list-style=amp | author2=Wolf, M. | title=Combining astrometry with the light-time effect: The case of VW Cep, zeta Phe and HT Vir| journal=Astronomische Nachrichten| volume=328| issue=9| pages=928–938| date=2007 | doi=10.1002/asna.200710828| bibcode=2007AN....328..928Z| s2cid=14956926}}</ref> Several publications have tried to set constrains to putative orbital period and minimum mass for unseen component. The most recent article<ref name="Zasche & Wolf" /> proposes an [[Astronomy:Orbital period|orbital period]] of 29.8 years for a [[Astronomy:Fusor|stellar object]] with roughly three fourths the [[Astronomy:Sun|Sun]]'s mass and high [[Astronomy:Orbital eccentricity|orbital eccentricity]] (e=0.66). Inclination is assumed being 33.6 [[Degree (angle)|degree]]s.
Nevertheless, hints of an additional body in the system still subsist and the authors infer a period of 77.46 years and eccentricity of 0.54 for unseen fourth component. Minimum mass is unclear, tentatively assumed being as small as 0.19 solar masses, as inferred by Pribulla et al. in 2000.<ref name="Pribulla et al.">{{cite journal | arxiv=0711.3980| author=Pribulla | author2=Chochol, D. | author3=Tremko, J. | author4=Parimucha, S. | author5=Vanko, M. | author6=Kreiner, J. M. | title=Period study of the contact system VW Cep| journal=Contributions of the Astronomical Observatory Skalnate Pleso| volume=30| issue=2| pages=117–139| year=2007| doi=10.1002/asna.200710828 | bibcode=2000CoSka..30..117P| s2cid=14956926 }}</ref> In any case orbital solutions are still blurry and further calculations are needed to provide a more robust model.

==References==
{{reflist|refs=

<ref name="Kreiner">{{cite journal |last1=Kreiner |first1=J. M. |last2=Winiarski |first2=M. |title=Photoelectric observations and light curve variations of VW Cephei |journal=Acta Astronomica |date=January 1981 |volume=31 |issue=3 |pages=351–361 |bibcode=1981AcA....31..351K |url=https://ui.adsabs.harvard.edu/abs/1981AcA....31..351K |access-date=7 December 2021}}</ref>

}}

{{Stars of Cepheus}}

{{DEFAULTSORT:VW Cephei}}
[[Category:Cepheus (constellation)]]
[[Category:Objects with variable star designations|Cephei, VW]]
[[Category:W Ursae Majoris variables]]
[[Category:Henry Draper Catalogue objects|197433]]
[[Category:G-type main-sequence stars]]
[[Category:Hipparcos objects|101750]]
[[Category:Durchmusterung objects]]
[[Category:Gliese and GJ objects|9703]]



{{Sourceattribution|VW Cephei}}