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{{Starbox begin
|name = HV 2112
}}
{{Starbox image
| image =
{{Location mark
|image=HV-2112.jpg|alt=HV-2112|float=center|width=300
|label=|position=center
|mark=Red circle.svg|mark_width=10|mark_link=HV 2112
|x=500|y=502
}}
| caption = HV 2112 (紅圈)
| credit ESA/Hubble and Digitized Sky Survey 2
}}
{{Starbox observe
|epoch = J2000.0
|constell = [[杜鵑座]]<ref name=constellation/>
|ra = {{RA|01|10|03.858}}<ref name=2mass/>
|dec = {{DEC|−72|36|52.62}}<ref name=2mass/>
|appmag_v=12.7 to below 16.7<ref name=kochanek/><ref name=shappee/>
}}
{{Starbox character
|type=[[漸近巨星支|AGB]]<ref name=beasor/>
|class = M5.5 II {{nowrap|(M3e – M7.5<ref name=wood/>)}}
| appmag_1_passband = [[J band (infrared)|J]]
| appmag_1 = 10.020<ref name=2mass/>
| appmag_2_passband = [[H band (infrared)|H]]
| appmag_2 = 9.100<ref name=2mass/>
| appmag_3_passband = [[K band (infrared)|K]]
| appmag_3 = 8.723<ref name=2mass/>
|b-v = +1.80<ref name=boyer/>
|u-b = +0.33<ref name=boyer/>
|variable = [[Mira variable|Mira]]?<ref name=gcvs/>
}}
{{Starbox astrometry
|radial_v = 157<ref name=levesque/>
|prop_mo_ra = +1.038<ref name=dr3/>
|prop_mo_dec = −1.274<ref name=dr3/>
|parallax = 0.0164
|p_error = 0.0246
|parallax_footnote=<ref name=dr3/>
|dist_ly =
|dist_pc =
|absmag_v = −5.2<ref name=levesque/>
}}
{{Starbox detail
|source=
|mass=~5<ref name=beasor/>
|radius=675 - 1,193<ref name=beasor/>{{efn | name=radius | 根據有效溫度和光度數據計算得出，參考標準太陽溫度為5,772 K: <math>\sqrt{(5772/3750)^4 * 81,283} = 675.4\ R\odot</math>
<math>\sqrt{(5772/2500)^4 * 50,119} = 1,193.4\ R\odot</math>}}
|luminosity=50,100 - 81,300<ref name=beasor/>
|temperature=2,500 - 3,750<ref name=beasor/>
|gravity=0.0<ref name=levesque/>
|metal_fe=−2.18<ref name=starhorse>{{cite journal |bibcode=2019A&A...628A..94A |title=Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia DR2 stars brighter than G = 18 |last1=Anders |first1=F. |last2=Khalatyan |first2=A. |last3=Chiappini |first3=C. |last4=Queiroz |first4=A. B. |last5=Santiago |first5=B. X. |last6=Jordi |first6=C. |last7=Girardi |first7=L. |last8=Brown |first8=A. G. A. |last9=Matijevič |first9=G. |last10=Monari |first10=G. |last11=Cantat-Gaudin |first11=T. |last12=Weiler |first12=M. |last13=Khan |first13=S. |last14=Miglio |first14=A. |last15=Carrillo |first15=I. |last16=Romero-Gómez |first16=M. |last17=Minchev |first17=I. |last18=De Jong |first18=R. S. |last19=Antoja |first19=T. |last20=Ramos |first20=P. |last21=Steinmetz |first21=M. |last22=Enke |first22=H. |journal=Astronomy and Astrophysics |volume=628 |pages=A94 |year=2019 |arxiv=1904.11302 |doi=10.1051/0004-6361/201935765 |s2cid = 131780028}}</ref>
|rotation=
|age =
}}
{{Starbox catalog
|names=[[Harvard Variable|HV]] 2112, [[2MASS]] J01100385-7236526, SMC V2156,<ref name=gcvs/> PMMR 187<ref name=SIMBAD>{{cite simbad|title=HV 2112|accessdate=2021-05-05}}</ref>
}}
{{Starbox reference
|Simbad=HV+2112
}}
{{Starbox end}}

'''HV 2112'''是一顆位於[[小麦哲伦星系]]的[[紅超巨星]]。該恆星被認為是可能性極高的[[索恩－祖特阔夫天体]]候選者。

== 概要 ==
天文學家於2014年以位於[[智利]]的[[麦哲伦望远镜]]中的克萊望遠鏡確認了HV 2112的存在<ref name="Eller">{{cite web|url=http://phys.org/news/2014-06-kip-thorne-discusses-discovery-thorne-zytkow.html|title=Kip Thorne discusses first discovery of Thorne-Zytkow object|last=Eller|first=Cynthia|date=30 June 2014|accessdate=30 June 2014|archive-date=2014-07-06|archive-url=https://web.archive.org/web/20140706054754/http://phys.org/news/2014-06-kip-thorne-discusses-discovery-thorne-zytkow.html|dead-url=no}}</ref>。該恆星的[[鋰]]、[[钼]]和[[铷]]元素豐度異常地高<ref name="Eller"/>。天文學家{{link-en|艾蜜莉·李維斯克|Emily Levesque}}（Emily Levesque）使用[[阿帕契點天文台]]的望遠鏡分析銀河系中的24顆紅超巨星，以及利用克萊望遠鏡觀測分別觀測[[大麥哲倫星系]]16顆和小麥哲倫星系24顆紅超巨星，發現了HV 2112這個索恩－祖特阔夫天体候選者<ref name="snc">{{cite web|url=http://www.sci-news.com/astronomy/science-thorne-zytkow-object-01970.html|title=First Thorne-Zytkow Object Found 200,000 Light-Years Away|date=5 June 2014|accessdate=30 June 2014|archive-date=2014-07-01|archive-url=https://web.archive.org/web/20140701180130/http://www.sci-news.com/astronomy/science-thorne-zytkow-object-01970.html|dead-url=no}}</ref>。

== 發現 ==
HV 2112 最早在 1908 年由[[亨丽爱塔·斯万·勒维特]]報告為變星。當時它被標記為哈佛編號 2112。雖然未給出具體的變光週期，但報告中指出其「可能為長週期」。根據攝影底片的觀測，其[[視星等]]範圍為13.7至暗於16.5。<ref name=hv/>

1966 年，對[[麥哲倫雲]]變星的分析顯示 HV 2112 的攝影星等範圍為13.0至暗於17.8。根據其大幅度且相當規律的光度變化（週期約為600天），它被歸類為長週期變星，也就是如今所稱的[[蒭藁變星]]。<ref name=pg/><ref name="Grady"/>

== 可能的天體類型 ==
[[File:HV2112LightCurve.png|thumb|left|HV 2112 的[[測光系統|可見光波段]][[光變曲線]]，繪製自 [[超新星全天自動巡天|ASAS-SN]] 數據<ref name="ASAS-SN"/>]]

=== 漸近巨星支星（AGB star） ===
HV 2112 過去一直被視為一顆極為明亮的[[漸近巨星支]]（AGB）星，即已耗盡核心氦燃料並處於[[恆星演化]]末期的[[紅巨星]]。大幅度的 M 型變星與光譜類型晚於 M5 的恆星，幾乎總是 AGB 星而非[[紅超巨星]]。這類恆星有理論上的最大光度，在小麥哲倫雲的距離下，HV 2112 的光度通常被計算為略高於此上限，約為 {{solar luminosity|60,000|link=y}} 倍太陽光度。<ref name=wood/>

較新的計算結果將 HV 2112 的光度估算為超過 {{solar luminosity|100,000}}，這已明確超出 AGB 星的範圍。這些計算考慮到 0.4 星等的星際[[消光]]，該值高於小麥哲倫雲中大質量恆星的平均值；然而對紅超巨星來說並不罕見，因為它們可能因鄰近恆星的環星塵埃導致額外的消光。<ref name=levesque/>

2016 年對 HV 2112 的[[自行]]分析顯示，其自行對於小麥哲倫雲內的恆星來說異常地大，雖然其[[徑向速度]]與 SMC 其他天體一致。其每年約 10 毫角秒的自行若真發生在 SMC 的距離下，表示其空間速度約為 3,100 公里/秒，遠高於該星系的逃逸速度。更可能的解釋是 HV 2112 實際上位於我們銀河系內，距離約為 3,000 秒差距，此時其光度應為 {{solar luminosity|1,000}}，而非 {{solar luminosity|100,000}}，是一顆典型的 AGB 星。重元素的過度豐富則可能是來自未被觀測到的伴星造成的「汙染」，形成所謂的[[S型星]]。<ref name=maccarone/> 也有其他研究認為其自行速度非常小，與位於 SMC 內的天體一致。<ref name=worley2016/><ref name=mcmillan/>

=== 索恩–日科夫天體（Thorne–Żytkow object） ===
2014 年，HV 2112 曾被認為可能是一顆[[索恩-祖特阔夫天体]]（TZO），這一發現來自智利的[[麦哲伦望远镜]]。為尋找 TZO 候選天體，[[Emily Levesque]] 使用[[阿帕契點天文台]]觀測了銀河系中的 24 顆紅超巨星，並利用 Magellan Clay 望遠鏡觀測了[[大麥哲倫雲]]中的 16 顆和小麥哲倫雲中的 22 顆。HV 2112 被發現含有異常高濃度的[[鋰]]、[[鉬]]和[[銣]]，而這些元素預期只會在 TZO 中產生。<ref name=levesque/>

2018 年一篇重新評估 HV 2112 性質的論文指出，未發現其具有異常的化學元素豐度，且其光度也低於先前估計。這表明該恆星不太可能是 TZO，更可能是一顆中等質量的[[漸近巨星支|AGB 星]]。<ref name=beasor/>

=== 雙星系統 ===
HV 2112 被[[OGLE]]星表列為未解析的多星系統。其[[自行]]與[[徑向速度]]皆與其他 SMC 恆星一致，[[視差]]雖為負值，但仍與如此遙遠天體的預期值相符。<ref name=gf/>

==參考資料==
{{reflist|refs=

<ref name=constellation>{{cite constellation|HV 2112}}</ref>

<ref name="Grady">{{cite journal |last1=O’Grady |first1=Anna J. G. |last2=Drout |first2=Maria R. |last3=Shappee |first3=B. J. |last4=Bauer |first4=Evan B. |last5=Fuller |first5=Jim |last6=Kochanek |first6=C. S. |last7=Jayasinghe |first7=T. |last8=Gaensler |first8=B. M. |last9=Stanek |first9=K. Z. |last10=Holoien |first10=Thomas W. S. |last11=Prieto |first11=J. L. |last12=Thompson |first12=Todd A. |title=Cool, Luminous, and Highly Variable Stars in the Magellanic Clouds from ASAS-SN: Implications for Thorne-Żytkow Objects and Super-asymptotic Giant Branch Stars |journal=The Astrophysical Journal |date=October 2020 |volume=901 |issue=2 |page=135 |doi=10.3847/1538-4357/abafad |doi-access=free |arxiv=2008.06563 |bibcode=2020ApJ...901..135O }}</ref>

<ref name="ASAS-SN">{{cite web |url=https://asas-sn.osu.edu/variables/lookup |website=ASAS-SN Variable Stars Database|title=ASAS-SN Variable Stars Database|publisher=ASAS-SN |access-date=6 January 2022}}</ref>

<ref name=beasor>{{cite journal |last1=Beasor |first1=Emma |last2=Davies |first2=Ben |last3=Cabrera-Ziri |first3=Ivan |last4=Hurst |first4=Georgia |title=A critical re-evaluation of the Thorne-Żytkow object candidate HV 2112 |journal=Monthly Notices of the Royal Astronomical Society |volume=479 |issue=3 |pages=3101 |date= 2 July 2018 |bibcode=2018MNRAS.479.3101B |doi=10.1093/mnras/sty1744 |doi-access=free |arxiv=1806.07399|s2cid=67766043 }}</ref>

<ref name=mcmillan>{{cite journal|arxiv=1804.10192v1|last1=McMillan|first1=Paul J|title=Gaia DR2 confirms that candidate Thorne-Żytkow object HV 2112 is in the SMC|journal=Research Notes of the AAS|volume=2|issue=2|pages=18|last2=Church|first2=Ross P|year=2018|doi=10.3847/2515-5172/aac0fb|bibcode=2018RNAAS...2...18M|s2cid=125376171 |doi-access=free }}</ref>

<ref name=gf>{{cite journal|bibcode=2015A&A...578A...3G|arxiv=1504.00003|title=A new survey of cool supergiants in the Magellanic Clouds|journal=Astronomy & Astrophysics|volume=578|pages=A3|last1=González-Fernández|first1=Carlos|last2=Dorda|first2=Ricardo|last3=Negueruela|first3=Ignacio|last4=Marco|first4=Amparo|year=2015|doi=10.1051/0004-6361/201425362|s2cid=55959019}}</ref>

<ref name=maccarone>{{cite journal|bibcode=2016MNRAS.458L...1M|arxiv=1601.05455|title=Large proper motion of the Thorne-Żytkow object candidate HV 2112 reveals its likely nature as foreground Galactic S-star|journal=Monthly Notices of the Royal Astronomical Society: Letters|volume=458|issue=1|pages=L1|last1=MacCarone|first1=Thomas J.|last2=De Mink|first2=Selma E.|author2-link=Selma de Mink|year=2016|doi=10.1093/mnrasl/slw004|doi-access=free |s2cid=119306614}}</ref>

<ref name=shappee>{{cite journal|bibcode=2014ApJ...788...48S|arxiv=1310.2241|title=The Man behind the Curtain: X-Rays Drive the UV through NIR Variability in the 2013 Active Galactic Nucleus Outburst in NGC 2617|journal=The Astrophysical Journal|volume=788|issue=1|pages=48|last1=Shappee|first1=B. J.|last2=Prieto|first2=J. L.|last3=Grupe|first3=D.|last4=Kochanek|first4=C. S.|last5=Stanek|first5=K. Z.|last6=De Rosa|first6=G.|last7=Mathur|first7=S.|last8=Zu|first8=Y.|last9=Peterson|first9=B. M.|last10=Pogge|first10=R. W.|last11=Komossa|first11=S.|last12=Im|first12=M.|last13=Jencson|first13=J.|last14=Holoien|first14=T. W.-S.|last15=Basu|first15=U.|last16=Beacom|first16=J. F.|last17=Szczygieł|first17=D. M.|last18=Brimacombe|first18=J.|last19=Adams|first19=S.|last20=Campillay|first20=A.|last21=Choi|first21=C.|last22=Contreras|first22=C.|last23=Dietrich|first23=M.|last24=Dubberley|first24=M.|last25=Elphick|first25=M.|last26=Foale|first26=S.|last27=Giustini|first27=M.|last28=Gonzalez|first28=C.|last29=Hawkins|first29=E.|last30=Howell|first30=D. A.|display-authors=9|year=2014|doi=10.1088/0004-637X/788/1/48|s2cid=119113433}}</ref>

<ref name=kochanek>{{cite journal|bibcode=2017PASP..129j4502K|arxiv=1706.07060|title=The All-Sky Automated Survey for Supernovae (ASAS-SN) Light Curve Server v1.0|journal=Publications of the Astronomical Society of the Pacific|volume= 129|issue= 980|last1=Kochanek|first1=C. S.|last2=Shappee|first2=B. J.|last3=Stanek|first3=K. Z.|last4=Holoien|first4=T. W.-S.|last5=Thompson|first5=Todd A.|last6=Prieto|first6=J.-L.|last7=Dong|first7=Subo|last8=Shields|first8=J. V.|last9=Will|first9=D.|last10=Britt|first10=C.|last11=Perzanowski|first11=D.|last12=Pojmanski|first12=G.|display-authors=9|year=2017|page=104502|doi=10.1088/1538-3873/aa80d9|s2cid=118995322}}</ref>

<ref name=pg>{{cite journal|bibcode=1966SCoA....9....1P|title=Variable Stars in the Small Magellanic Cloud|journal=Smithsonian Contributions to Astrophysics|volume=9|pages=1–205|last1=Payne-Gaposchkin|first1=Cecilia|last2=Gaposchkin|first2=Sergei|year=1966|doi=10.5479/si.00810231.9.1}}</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=levesque>{{Cite journal|title=Discovery of a Thorne-̇Żytkow object candidate in the Small Magellanic Cloud|journal=Monthly Notices of the Royal Astronomical Society: Letters|volume=443|pages=L94–L98|last=Levesque|first=Emily|author1-link=Emily Levesque|date=1 September 2014|arxiv=1406.0001|bibcode = 2014MNRAS.443L..94L |doi = 10.1093/mnrasl/slu080 |doi-access=free |s2cid=119192926}}</ref>

<ref name=2mass>{{cite journal |bibcode=2003yCat.2246....0C |title=VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003) |journal=CDS/ADC Collection of Electronic Catalogues |pages=II/246 |volume=2246 |last1=Cutri |first1=Roc M. |last2=Skrutskie |first2=Michael F. |last3=Van Dyk |first3=Schuyler D. |last4=Beichman |first4=Charles A. |last5=Carpenter |first5=John M. |last6=Chester |first6=Thomas |last7=Cambresy |first7=Laurent |last8=Evans |first8=Tracey E. |last9=Fowler |first9=John W. |last10=Gizis |first10=John E. |last11=Howard |first11=Elizabeth V. |last12=Huchra |first12=John P. |last13=Jarrett |first13=Thomas H. |last14=Kopan |first14=Eugene L. |last15=Kirkpatrick |first15=J. Davy |last16=Light |first16=Robert M. |last17=Marsh |first17=Kenneth A. |last18=McCallon |first18=Howard L. |last19=Schneider |first19=Stephen E. |last20=Stiening |first20=Rae |last21=Sykes |first21=Matthew J. |last22=Weinberg |first22=Martin D. |last23=Wheaton |first23=William A. |last24=Wheelock |first24=Sherry L. |last25=Zacarias |first25=N. |year=2003 |url=http://vizier.u-strasbg.fr/viz-bin/VizieR?-source=II/246 }}</ref>

<ref name=wood>{{cite journal|bibcode=1983ApJ...272...99W|title=Long-period variables in the Magellanic Clouds – Supergiants, AGB stars, supernova precursors, planetary nebula precursors, and enrichment of the interstellar medium|url=https://archive.org/details/sim_astrophysical-journal_1983-09-01_272_1/page/98|journal=Astrophysical Journal|volume=272|pages=99|last1=Wood|first1=P. R.|last2=Bessell|first2=M. S.|last3=Fox|first3=M. W.|year=1983|doi=10.1086/161265|doi-access=free}}</ref>

<ref name=hv>{{cite journal|bibcode=1907AnHar..60...87L|title=1777 variables in the Magellanic Clouds|journal=Annals of Harvard College Observatory|volume=60|pages=87|last1=Leavitt|first1=Henrietta S.|year=1908}}</ref>

<ref name=boyer>{{cite journal|bibcode=2011AJ....142..103B|arxiv=1106.5026|title=Surveying the Agents of Galaxy Evolution in the Tidally Stripped, Low Metallicity Small Magellanic Cloud (SAGE-SMC). II. Cool Evolved Stars|journal=The Astronomical Journal|volume=142|issue=4|pages=103|last1=Boyer|first1=Martha L.|last2=Srinivasan|first2=Sundar|last3=Van Loon|first3=Jacco Th.|last4=McDonald|first4=Iain|last5=Meixner|first5=Margaret|last6=Zaritsky|first6=Dennis|last7=Gordon|first7=Karl D.|last8=Kemper|first8=F.|last9=Babler|first9=Brian|last10=Block|first10=Miwa|last11=Bracker|first11=Steve|last12=Engelbracht|first12=Charles W.|last13=Hora|first13=Joe|last14=Indebetouw|first14=Remy|last15=Meade|first15=Marilyn|last16=Misselt|first16=Karl|last17=Robitaille|first17=Thomas|last18=Sewiło|first18=Marta|last19=Shiao|first19=Bernie|last20=Whitney|first20=Barbara|display-authors=9|year=2011|doi=10.1088/0004-6256/142/4/103|s2cid=119268816}}</ref>

<ref name=worley2016>{{cite journal |doi=10.1093/mnrasl/slw034 |title=The proper motion of HV2112: A TŻO candidate in the SMC |journal=Monthly Notices of the Royal Astronomical Society: Letters |volume=459 |issue=1 |pages=L31–L35 |year=2016 |last1=Worley |first1=C. Clare |last2=Irwin |first2=Mike. J. |last3=Tout |first3=Christopher A. |last4=Żytkow |first4=Anna N. |last5=Fraser |first5=Morgan |last6=Izzard |first6=Robert G. |doi-access=free |bibcode=2016MNRAS.459L..31W |arxiv=1602.08479 |s2cid=118463486 }}</ref>

<ref name=dr3>{{cite Gaia DR3|4687439865638979712}}</ref>

}}

==備註==
{{notelist}}

{{Stars of Tucana}}

[[Category:杜鵑座]]
[[Category:麥哲倫雲]]
[[Category:M型亮巨星]]
[[Category:银河系外恒星]]
[[Category:小麥哲倫星系]]

HV 2112 - 版本历史

imported>InternetArchiveBot：​Add 1 book for verifiability (20251017sim)) #IABot (v2.0.9.5) (GreenC bot

imported>InternetArchiveBot：Add 1 book for verifiability (20251017sim)) #IABot (v2.0.9.5) (GreenC bot