{{short description|Triple star system in constellation Draco}} {{Sky|15|33|51.0571|+|63|54|25.6950}} {{Starbox begin }} {{Starbox image | image = [[Image:TWDraLightCurve.png|250px]] | caption = A [[light curve]] for TW Draconis, plotted from [[Transiting Exoplanet Survey Satellite|''TESS'']] data<ref name=MAST/> }} {{Starbox observe | epoch = J2000 | ra = {{RA|15|33|51.0571}}<ref name=DR3A/> | dec = {{DEC|+63|54|25.695}}<ref name=DR3A/> | appmag_v = 7.46<ref name=SIMBAD>{{cite simbad |title=TW Dra|access-date=2021-12-13}}</ref> | constell = [[Draco (constellation)|Draco]] }} {{Starbox character | component1=HD 139319A |component2=HD 139319B | type = |type2= | class =A8V+K0III<ref name=Kim2003/> |class2=F7V{{cn|date=April 2026}} | appmag_1_passband = g | appmag_1 = 7.39<ref name=DR3A/> | appmag_1_passband2 = g | appmag_1_2 = 9.65<ref name=DR3B/> }} {{Starbox astrometry |component1=HD 139319A | radial_v = | prop_mo_ra = 11.44{{±|0.03}} | prop_mo_dec = 22.39{{±|0.02}} | pm_footnote=<ref name=DR3A/> | parallax =6.0571 | p_error = 0.0179 | parallax_footnote = <ref name=DR3A/> | absmag_v = | component2 = HD 139319B | radial_v2 = 1.6{{±|0.7}}<ref name=DR3B/> | prop_mo_ra2 = 12.09{{±|0.02}} | prop_mo_dec2 = 21.278{{±|0.018}} | pm_footnote2 = <ref name=DR3B/> | parallax2 = 6.0345 | p_error2 = 0.0160 | parallax_footnote2 = <ref name=DR3B/> | absmag_v2 = <!--Absolute magnitude (Johnson-Cousins V system)--> }} {{Starbox orbit | reference = <ref name=Tkachenko2010>{{citation |bibcode=2016RAA....16...94L |doi=10.1088/1674-4527/16/6/094 |title=Lunar-based Ultraviolet Telescope study of the well-known Algol-type binary TW Dra |year=2016 |last1=Liao |first1=Wen-Ping |last2=Qian |first2=Sheng-Bang |last3=Zejda |first3=Miloslav |last4=Zhu |first4=Li-Ying |last5=Li |first5=Lin-Jia |journal=Research in Astronomy and Astrophysics |volume=16 |issue=6 |page=009 |s2cid=124656327 |doi-access=free }}</ref> | primary = TW Draconis A | name = TW Draconis B | period = <!--Period (in years)--> | period_unitless = 2.8068491 [[day|d]] | axis = | axis_unitless =0.057 [[astronomical unit|AU]] | eccentricity = | inclination = 86.8 | node = <!--Longitude of node (in degrees)--> | periastron = <!--Periastron epoch--> | periarg = <!--Argument of periastron (in degrees), secondary --> | periarg_primary = <!--Argument of periastron (in degrees), primary --> | k1 = 64.05 | k2 = 150 }} {{Starbox detail |source=<ref>{{citation |bibcode=2013IBVS.6086....1B |title=Standard UBV photometry and improved physical properties of TW Dra |last1=Bozic |first1=H. |last2=Nemravova |first2=J. |last3=Harmanec |first3=P. |journal=Information Bulletin on Variable Stars |year=2013 |volume=6086 |page=1 }}</ref> | component1 =TW Draconis A | mass = 2.16{{±|0.11}} | radius =2.64{{±|0.04}} | temperature = 7815{{±|92}} |gravity= 3.928{{±|0.026}} | luminosity = | metal_fe= |rotation= | rotational_velocity= | age_gyr = | component2 = TW Draconis B | mass2 = 0.93{{±|0.05}} | radius2= 3.66{{±|0.06}} |gravity2= 3.314{{±|0.026}} | temperature2 =4442{{±|32}} | luminosity2 = | age_myr2 = }} {{Starbox catalog |component1=HD 139319A |component2=HD 139319B | names = BD+64 1077, HIP 76196, [[2MASS]] J15335104+6354257, GSC 04184-00061 | names1=TW Draconis, TYC 4184-61-1, Gaia DR2 1640708022815757568 | names2=TYC 4184-61-2, Gaia DR2 1640708022815757824 }} {{Starbox reference | Simbad = HD+139319 }} {{Starbox end}}
'''HD 139319''' is a ternary system composed of the binary [[Algol variable]] star known as TW Draconis, and a [[Main sequence|main-sequence]] companion star at a separation of 3 arcseconds.<ref name=Tkachenko2010/> The system lies in the constellation of [[Draco (constellation)|Draco]] about {{val|540|ul=light years}} away.
== System == The primary star is an eclipsing, semi-detached binary, the brighter component of which is a pulsating star of [[Delta Scuti variable|Delta Scuti]] type. Its pulsation frequency is 17.99 cycles per day.<ref name=Kim2003>{{citation |doi=10.1051/0004-6361:20030630 |bibcode=2003A&A...405..231K |title=Search for A–F Spectral type pulsating components in Algol-type eclipsing binary systems |year=2003 |last1=Kim |first1=S.-L. |last2=Lee |first2=J. W. |last3=Kwon |first3=S.-G. |last4=Youn |first4=J.-H. |last5=Mkrtichian |first5=D. E. |last6=Kim |first6=C. |journal=Astronomy & Astrophysics |volume=405 |pages=231–236 |doi-access=free }}</ref> Mass transfer between stars is ongoing in the system<ref>{{citation|arxiv=1601.03198|year=2016|title=SuperWASP discovery and SALT confirmation of a semi-detached eclipsing binary that contains aδScuti star|doi=10.1051/0004-6361/201526881|last1=Norton|first1=A. J.|last2=Lohr|first2=M. E.|last3=Smalley|first3=B.|last4=Wheatley|first4=P. J.|last5=West|first5=R. G.|journal=Astronomy & Astrophysics|volume=587|pages=A54|bibcode=2016A&A...587A..54N|s2cid=10625309}}</ref> with a transfer rate of 6.8×10<sup>−7</sup>{{Solar_mass}}/year. The 2.8 day period of the Algol binary is cyclically variable with a period 116.04 years, possibly due to gravitational influence of the distant companion HD 139319B. Another three stars in the system are suspected.<ref name=Tkachenko2010/>
== References == {{Reflist|refs= <ref name=DR3A>{{cite Gaia DR3|1640708022815757568}}</ref> <ref name=DR3B>{{cite Gaia DR3|1640708022815757824}}</ref> <ref name=MAST>{{cite web |title=MAST: Barbara A. Mikulski Archive for Space Telescopes |url=https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html |publisher=Space Telescope Science Institute |access-date=8 December 2021}}</ref> }}
{{Draco (constellation)}} [[Category:Triple star systems|3]] [[Category:Draco (constellation)]] [[Category:Durchmusterung objects|BD+64 1077]] [[Category:Hipparcos objects|076196]] [[Category:Henry Draper Catalogue objects|139319]] [[Category:G-type main-sequence stars]] [[Category:K-type giants]] [[Category:F-type main-sequence stars]] [[Category:Algol variables]] [[Category:Objects with variable star designations|Draconis, TW]]