View source for 15 Vulpeculae

{{Short description|A-type giant star in the constellation Vulpecula}}
{{Starbox begin
| name = 15 Vulpeculae
}}
{{Starbox image
|image=
{{Location mark
|image=Vulpecula constellation map.svg|alt=|float=center|width=280
|label=|position=right
|mark=Red circle.svg|mark_width=10|mark_link=15 Vulpeculae
|x=564|y=316
}}
|caption=Location of 15 Vulpeculae (circled)
}}
{{Starbox observe
| epoch = J2000
| constell = [[Vulpecula]]
| ra = {{RA|20|01|06.0486}}<ref name="Gaia EDR3"/>
| dec = {{DEC|+27|45|12.863}}<ref name="Gaia EDR3"/>
| appmag_v = 4.66<ref name=XHIP/> (4.62 - 4.67)<ref name=gcvs/>
}}
{{Starbox character
| class = A4IIIm<ref name=gcvs/> or {{nowrap|kA5hA7mA7 (IV–V)}}<ref name=Çay2016/>
| b-v = +0.18<ref name=MermiliodUBV/>
| u-b = +0.15<ref name=MermiliodUBV/>
| variable = [[Alpha2 Canum Venaticorum variable|α<sup>2</sup> CVn]]<ref name=gcvs/>
}}
{{Starbox astrometry
| radial_v = −26.10<ref name=Gontcharov2006/>
| prop_mo_ra = {{val|57.817|0.081}}<ref name="Gaia EDR3"/>
| prop_mo_dec = {{val|3.994|0.085}}<ref name="Gaia EDR3"/>
| parallax = 13.4427
| p_error = 0.1050
| parallax_footnote = <ref name="Gaia EDR3"/>
| absmag_v = 0.36<ref name=XHIP/>
}}
{{Starbox detail
| mass = 2.41<ref name=Cay2025/>
| temperature = {{val|7,685|100|fmt=commas}}<ref name=Cay2025/>
| luminosity = 61.6<ref name=Cay2025/>
| radius = {{solar radius calculator|type=logLT|1.79|7685|decimals=2}}<ref name=Cay2025/>{{Efn|name=rad|1=Calculated, using the [[Stefan-Boltzmann law]] and the star's [[effective temperature]] and luminosity, with respect to the [[Sun|solar]] nominal effective temperature of {{val|fmt=commas|5,772|ul=K}}:<math display="block">\sqrt{\biggl(\frac{5,772}{7,685}\biggr)^4 \cdot 10^{1.79}} = 4.43\ R_\odot.</math>}}
| rotational_velocity = 15.0<ref name=Glebocki2005/>
| gravity = 3.53<ref name=Cay2025/>
| metal_fe = +0.02<ref name=XHIP/>
}}
{{Starbox catalog
| names = {{odlist | V=NT Vul | F=15 Vul | BD=+27°3587 | FK5=1523 | HD=189849 | HIP=98543 | HR=7653 | SAO=88071 | GC=27753 }}<ref name="Simbad"/>
}}
{{Starbox reference
| Simbad = 15+Vulpeculae
}}
{{Starbox end}}

'''15 Vulpeculae''' is a [[variable star]] in the northern [[constellation]] of [[Vulpecula (constellation)|Vulpecula]], located approximately 243 light years away based on [[parallax]] measurements.<ref name="Gaia EDR3"/> It has the [[variable star designation]] '''NT Vulpeculae'''; ''15 Vulpeculae'' is the [[Flamsteed designation]]. It is visible to the naked eye as a faint, white-hued star with a typical [[apparent visual magnitude]] of 4.66.<ref name=XHIP/> This object is moving closer to the Earth with a heliocentric [[radial velocity]] of {{val|−26|u=km/s}}.<ref name=Gontcharov2006/>

[[File:NTVulLightCurve.png|thumb|An [[Photometric_system#Photometric_letters|ultraviolet band]] [[light curve]] for NT Vulpeculae, adapted from Kuvshinov ''et al.'' (1976)<ref name="Kuvshinov"/>|center]]
The star is considered a marginal [[Am star]] with a [[stellar classification]] of A4&nbsp;IIIm,<ref name=gcvs/> matching an [[stellar evolution|evolved]] [[A-type star|A-type]] [[giant star]]. However, Gray & Garrison (1989) found a class of kA5hA7mA7 (IV–V),<ref name=Çay2016/> which matches a blend of [[subgiant star|subgiant]] and [[main sequence]] [[luminosity class]]es with the [[Calcium K line|K-line]] (kA5) of an A5 star and the [[Hydrogen spectral series|hydrogen]] (hA7) and [[metallicity|metal]] (mA7) [[absorption line]]s of an A7 star. 15 Vulpeculae was a typical Am star when a [[main sequence]], when evolving into a subgiant, it lost most of the peculiar properties of an Am star but still maintain some element abundance peculiarities.<ref name=Cay2025/> The star is 2.4 times more massive than the Sun and has expanded to four times the Sun's diameter.{{efn|name=rad}} It is radiating 62 times the [[Sun's luminosity]] from its [[photosphere]] at an [[effective temperature]] of {{val|fmt=commas|7685|u=K}}.<ref name=Cay2025/> It is an [[Alpha2 Canum Venaticorum variable|Alpha<sup>2</sup> Canum Venaticorum]]-type variable with magnitude ranging from 4.62 down to 4.67 over a period of 14 days.<ref name=gcvs/>

There is evidence that 15 Vulpeculae may have a [[binary star|companion star]], given the high margins of error in the [[astrometry|astrometric]] measurements taken by [[Gaia DR3]], as well as its unusually slow [[projected rotational velocity]], which could also be explained if the star is being viewed pole-on.<ref name=Cay2025/>
{{clear left}}

==Notes==
{{notelist}}

==References==
{{Reflist|refs=

<ref name="Gaia EDR3">{{Cite Gaia DR3|2027458764012840576}}</ref>

<ref name=Cay2025>{{Cite journal |last1=Çay |first1=M. Taşkın |last2=Çay |first2=İpek H. |last3=Civelekler |first3=Betül |journal=Monthly Notices of the Royal Astronomical Society |title=A critical evaluation of the elemental abundances and evolutionary status of 15 Vul (HD 189849): The first identification of an evolved Am star |date=2025-01-13 |volume=537 |issue=4 |pages=3054–3065 |arxiv=2501.07504 |doi=10.1093/mnras/staf034 |doi-access=free |bibcode=2025MNRAS.537.3054C |s2cid=275463214 |type=Accepted manuscript}}</ref>

<ref name="Simbad">{{cite simbad | title=15 Vul | access-date=2018-03-15 }}</ref>

<ref name=MermiliodUBV>{{cite journal | bibcode=2006yCat.2168....0M | title=VizieR Online Data Catalog: Homogeneous Means in the UBV System (Mermilliod 1991) | journal=VizieR On-line Data Catalog: II/168. Originally Published in: Institut d'Astronomie | volume=2168 | last1=Mermilliod | first1=J. C. | year=2006 }}[http://vizier.u-strasbg.fr/viz-bin/VizieR-4?-source=II/168/ubvmeans&LID=%2B100189849 Vizier catalog entry]</ref>

<ref name="Kuvshinov">{{cite journal |last1=Kuvshinov |first1=V. M. |last2=Hildebrandt |first2=G. |last3=Schoeneich |first3=W. |title=Photoelektrische Untersuchungen des Magnetfeldes und der Helligkeit der Am-Sterne 15 VUL und 68 Tau |journal=Astronomische Nachrichten |date=January 1976 |volume=297 |issue=4 |pages=181–188 |doi=10.1002/asna.19762970405 |bibcode=1976AN....297..181K }}</ref>

<ref name=gcvs>{{cite journal | bibcode=2009yCat....102025S |title=VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)|journal=VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S|volume=1|display-authors=etal|last1=Samus|first1=N. N.|last2=Durlevich|first2=O. V.|year=2009}}</ref>

<ref name=Çay2016>{{cite journal
 | title=Elemental Abundance Analyses with DAO Spectrograms. XXXIX. The Am Stars 2 UMa and 15 Vul
 | last1=Çay | first1=İpek H.
 | last2=Teker Yelkenci | first2=Aysegul
 | last3=Adelman | first3=Saul J.
 | journal=Publications of the Astronomical Society of the Pacific
 | volume=128 | issue=963 | page=054201 | date=May 2016
 | doi=10.1088/1538-3873/128/963/054201 | bibcode=2016PASP..128e4201C | s2cid=123542297 }}</ref>

<ref name=Glebocki2005>{{cite journal | bibcode=2005yCat.3244....0G | title=VizieR Online Data Catalog: Catalog of Stellar Rotational Velocities (Glebocki+ 2005) | journal=VizieR On-line Data Catalog: III/244. Originally Published in: 2005csss...13..571G; 2005yCat.3244....0G | volume=3244 | last1=Glebocki | first1=R. | last2=Gnacinski | first2=P. | year=2005 }} [http://vizier.u-strasbg.fr/viz-bin/VizieR-4?-source=III/244/catalog&HIP=98543 Vizier catalog entry]</ref>

<ref name=XHIP>{{cite journal | bibcode=2012AstL...38..331A | doi=10.1134/S1063773712050015 | arxiv=1108.4971 | title=XHIP: An extended hipparcos compilation | journal=Astronomy Letters | volume=38 | issue=5 | pages=331 | year=2012 | last1=Anderson | first1=E. | last2=Francis | first2=Ch. | s2cid=119257644 }} [http://vizier.u-strasbg.fr/viz-bin/VizieR-4?-source=V/137D/XHIP&HIP=98543 Vizier catalog entry]</ref>

<ref name=Gontcharov2006>{{Cite journal | doi=10.1134/S1063773706110065 | bibcode=2006AstL...32..759G| title=Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system| journal=Astronomy Letters| volume=32| issue=11| pages=759–771| year=2006| last1=Gontcharov| first1=G. A.|arxiv = 1606.08053 | s2cid=119231169}}</ref>

}}

{{Stars of Vulpecula}}
{{Sky|20|01|06.0486|+|27|45|12.863}}

{{DEFAULTSORT:15 Vulpeculae}}
[[Category:A-type giants]]
[[Category:Am stars]]
[[Category:Alpha2 Canum Venaticorum variables]]
[[Category:Vulpecula]]
[[Category:Durchmusterung objects]]
[[Category:Flamsteed objects|Vulpeculae, 15]]
[[Category:Henry Draper Catalogue objects|189849]]
[[Category:Hipparcos objects|098543]]
[[Category:Bright Star Catalogue objects|7653]]
[[Category:Objects with variable star designations|Vulpeculae, NT]]