当前位置：文档之家 › A 10-micron Search for Inner-Truncated Disks Among Pre-Main-Sequence Stars With Photometric

A 10-micron Search for Inner-Truncated Disks Among Pre-Main-Sequence Stars With Photometric

  • 格式：pdf
  • 大小：360.57 KB
  • 文档页数：37

arXiv:astro-ph/0010657v1 31 Oct 2000A10µmSearchforInner-TruncatedDisksAmongPre-Main-SequenceStarswithPhotometricRotationPeriods

KeivanG.Stassun1andRobertD.Mathieu1

FrederickJ.Vrba2

TseviMazeh3

ArneHenden2Received–2–

ABSTRACT

Weusemid-IR(primarily10µm)photometryasadiagnosticforthepres-

enceofdiskswithinnercavitiesamong32pre-mainsequencestarsinOrion

andTaurus-Aurigaforwhichrotationperiodsareknownandwhichdonotshow

evidenceforinnerdisksatnear-IRwavelengths.Diskswithinnercavitiesare

predictedbymagneticdisk-lockingmodelsthatseektoexplaintheregulation

ofangularmomentuminTTauristars.Onlythreestarsinoursampleshow

evidenceforexcessmid-IRemission.Whilethesethreestarsmaypossesstrun-

cateddisksconsistentwithmagneticdisk-lockingmodels,theremaining29stars

inoursampledonot.Apparently,starslackingnear-IRexcessesingeneraldo

notpossesstruncateddiskstowhichtheyaremagneticallycoupled.

Wediscusstheimplicationsofthisresultforthehypothesisofdisk-regulated

angularmomentum.Evidently,youngstarscanexistasslowrotatorswithout

theaidofpresentdisk-locking,andthereexistveryyoungstarsalreadyrotating

nearbreakupvelocitywhosesubsequentangularmomentumevolutionwillnotbe

regulatedbydisks.Moreover,wequestionwhetherdisks,whenpresent,truncate

inthemannerrequiredbydisk-lockingscenarios.Finally,wediscusstheneed

forrotationalevolutionmodelstotakefullaccountofthelargedispersionof

rotationratespresentat1Myr,whichmayallowthemodelstoexplainthe

rotationalevolutionoflow-masspre-mainsequencestarsinawaythatdoesnot

dependuponbrakingbydisks.

Subjectheadings:accretion,accretiondisks—stars:evolution—stars:

formation—stars:pre-mainsequence—stars:rotation–3–

1.Introduction

Akeystoneofthecurrentparadigmofrotationalevolutionamonglow-masspre-main-

sequence(PMS)starsistheregulationofstellarangularmomentumbycircumstellar

disks.Indeed,mostrotationalevolutionmodelstodayrelychieflyuponsomeformof

disk-regulatedstellarangularmomentumtoconnecttherotationalpropertiesofTTauri

stars(TTS)tothoseofzero-agemainsequence(ZAMS)stars(Bouvier,Forestini,&Allain

1997;Krishnamurthietal.1997;CollierCameron,Campbell,&Quaintrell1995).The

theoreticaledificesupportingthedisk-regulationparadigmhasbeendevelopedbyseveral

researchers(K¨onigl1991;Ostriker&Shu1995;Yi1995;CollierCameron&Campbell

1993;Ghosh&Lamb1979a,1979b),whereinasteady-state,magneticallymediated,

star-diskcouplingmechanismkeepsthestaratroughlyconstantangularvelocityforthe

lifetimeofthedisk,preventingthestarfromspinningupasitcontracts.Thismagnetic

disk-lockingmodelprovidesanattractivesolutiontothelong-standingpuzzleofhowstars

depleteangularmomentumastheyevolvetothemainsequence(Stauffer&Hartmann

1987).

Observationalinvestigationsofdisk-regulatedangularmomentumhaveyieldedmixed

results.Insupportofdisk-locking,severalauthorshave,eitherdirectlyorindirectly,linked

diskstoslowstellarrotation.Forexample,Herbstandcollaborators(Choi&Herbst1996,

andreferencestherein)havereportedthedistributionofTTSrotationperiodsintheOrion

NebulaCluster(ONC)tobedistinctlybimodal.Theslowrotators(Prot>4days),they

suggest,representthosestarsthatarepresently,orwereuntilrecently,disk-locked.More

directsupporthasbeenpresentedbyEdwardsetal.(1993),whoreportedacorrelation

betweenthepresenceofexcessnear-IRemissionandslowstellarrotationamong34TTSin

TaurusandOrion.ConsideringstarsintheirsamplelaterthanK5,thoseauthorsfound

excessnear-IRemissionamongnoneoftherapidrotatorsbutamonghalfoftheslow–4–

rotators.Bouvieretal.(1993)reportedsimilarresultsamong26TTSinTaurus-Auriga.

TheyfoundthattheclassicalTTS(CTTS;thoseshowingevidenceofactiveaccretionand

circumstellardisks)intheirsamplerotatemoreslowlyonaveragethantheirweak-lined

(WTTS)counterparts.Incontrasttothesestudies,wedidnotfindstrongevidencefora

bimodaldistributionofrotationperiods,nordidwefindevidenceforalinkagebetween

disksandslowstellarrotation,inourownstudyofdisksandstellarrotationinOrion

(Stassunetal.1999,hereafterPaperI;seealsoStassunetal.2000foraconcisesummary).

Among254starswith0.1

bestatisticallyconsistentwithauniformdistribution.Moreover,wefoundnear-IRexcesses

tobepresentwithroughlyequalfrequencyamongbothslowandrapidrotatorswhenwe

combinedourrotationperiodswithnear-IRphotometryfromtheliterature(Hillenbrandet

al.1998)formorethan100starsinoursample.

Herbstetal.(2000)haveshownthatsubdividingtheONCsamplebymasscan

reconcilesomeofthesecontradictoryfindings.Theyfindthatthebimodaldistributionof

rotationperiodsinOrionholdstruewhentheyconsideronlystarswithM⋆>0.25M⊙,i.e.

earlierthanaboutM3.Forthesestars,theyalsofindaweakbutstatisticallysignificant

correlationbetweennear-IRexcessandstellarrotationperiod;theslowerrotatorstendto

exhibitlargernear-IRexcesses.

WhethertheseIRobservationsofTTSinfactagreewiththepredictionsofdisk-locking

合集下载

2020年广东省中小学生 天文知识竞赛试题(低年组)

2020年广东省中小学生 天文知识竞赛试题(低年组)

2020年广东省中小学生

天文知识竞赛试题（低年组）

注意事项：

1、本卷为闭卷考试，请答卷人按照自己的真实水平独立完成。

2、选择题全部为单项选择，考生直接在试题页面中点选一个最接近正确的答案，答错不扣分。

3、总分100分，每题2分，考试时间100分钟。

4、本场考试允许使用不具编程功能的计算器。

5、考试过程中不得切出考试页面，否则平台将自动收卷。

6、比赛结果将在广东天文学会网站和微信公众号公布。

_______________________________________________________________________________________________

Part 1. 天文热点

1. 我国首个自主发射的火星探测器“天问一号”计划于何时入轨火星？ B

A. 2020年12月底左右 B. 2021年2月底左右

C. 2021年5月中左右 D. 2022年7月底左右

2. 我国嫦娥五号探测器在今年何时发射升空？ C

A. 12月24日 B. 12月7日 C. 11月24日 D. 11月28日

3. 2020年的诺贝尔物理学奖分别颁发给罗杰·彭罗斯、莱因哈特·根策尔和安德烈娅·盖兹。其中彭罗斯获奖的理由是“发现黑洞形成是广义相对论的一个预言”，那根策尔和盖兹获奖的理由是？ A

A. 发现银河系中心的超大质量致密天体

B. 发现第一颗环绕类太阳恒星运动的系外行星

C. 验证了引力波的存在

D. 发现了一种测量宇宙大尺度结构的探针

4. 以下哪所高校在今年正式成立天文系？ D

A. 香港科技大学 B. 贵州大学 C. 中山大学 D. 广州大学

5. 今年7月，一颗“黑马”彗星亮度达到2等以上，吸引了很多爱好者拍摄。这颗彗星是？C

A. C/2019 Y4 (ATLAS) B. C/2020 F8 (SWAN)

引力波观测原文PhysRevLett.116.061102

引力波观测原文PhysRevLett.116.061102

ObservationofGravitationalWavesfromaBinaryBlackHoleMerger

B.P.Abbottetal.*

(LIGOScientificCollaborationandVirgoCollaboration)(Received21January2016;published11February2016)

OnSeptember14,2015at09:50:45UTCthetwodetectorsoftheLaserInterferometerGravitational-WaveObservatorysimultaneouslyobservedatransientgravitational-wavesignal.Thesignalsweepsupwardsinfrequencyfrom35to250Hzwithapeakgravitational-wavestrainof1.0×10−21.Itmatchesthewaveformpredictedbygeneralrelativityfortheinspiralandmergerofapairofblackholesandtheringdownoftheresultingsingleblackhole.Thesignalwasobservedwithamatched-filtersignal-to-noiseratioof24andafalsealarmrateestimatedtobelessthan1eventper203000years,equivalenttoasignificancegreater

than5.1σ.Thesourceliesataluminositydistanceof410þ160−180Mpccorrespondingtoaredshiftz¼0.09þ0.03−0.04.

Inthesourceframe,theinitialblackholemassesare36þ5−4M⊙and29þ4−4M⊙,andthefinalblackholemassis62þ4−4M⊙,with3.0þ0.5−0.5M⊙c2radiatedingravitationalwaves.Alluncertaintiesdefine90%credibleintervals.Theseobservationsdemonstratetheexistenceofbinarystellar-massblackholesystems.Thisisthefirstdirectdetectionofgravitationalwavesandthefirstobservationofabinaryblackholemerger.

Physics Letters B

Physics Letters B

DESY02-096ISSN0418-9833

July2002

SearchforExcitedElectronsatHERA

H1Collaboration

Abstract

Asearchforexcitedelectron(e∗

)productionisdescribedinwhichtheelectroweakdecays

e∗

→eγ,e∗

→eZande∗

→νWareconsidered.Thedatausedcorrespondtoan

integratedluminosityof120pb−1

takenine±

pcollisionsfrom1994to2000withtheH1

detectoratHERAatcentre-of-massenergiesof300and318GeV.Noevidenceforasignal

isfound.Massdependentexclusionlimitsarederivedfortheratioofthecouplingstothe

compositenessscale,f/Λ.Theselimitsextendtheexcludedregiontohighermassesthan

hasbeenpossibleinpreviousdirectsearchesforexcitedelectrons.

Tobesubmittedto

PhysicsLettersBC.Adloff33

,V.Andreev24

,B.Andrieu27

,T.Anthonis4

,A.Astvatsatourov35

,A.Babaev23

,

J.B¨ahr35

,P.Baranov24

,E.Barrelet28

,W.Bartel10

,S.Baumgartner36

,J.Becker37

,

M.Beckingham21

,A.Beglarian34

,O.Behnke13

,A.Belousov24

,Ch.Berger1

近距恒星列表

近距恒星列表

除了比邻星外，邻近太阳系的恒星由近而远的十颗依序为：

1、半人马座α星（αCen）4.3光年

2、巴纳德星（Barnard's）5.86光年

3、伍尔夫359星（Wolf359）7.7光年

4、勃兰得2147星（BD+36°）8.2光年

5、鲸鱼座uv星（Luyten726-8）8.4光年

6、天狼星（Sirius，大犬座α星）8.7光年

7、罗斯154星（Ross 154）9.5光年

8、罗斯248星（Ross 248）10.4光年

9、波江座ε星（εEri）10.8光年

10、罗斯128星（Ross 128）10.9光年

近距恒星列表

# 名称 恒星

类形 mV MV Teff

K(±err) 历元 J2000.0 视差[2][3]

”(±err) 距离[4]

光年(±err) 附加

参考资料

系统 恒星 RA[2] Dec[2]

太阳系 太阳 G2V[2] −26.72[2] 4.85[2] 5,778[5] — — 180° 0.0000158(3)

or

approx. 8 光分

1 半人马座α

(Rigil

Kentaurus;

Toliman) 半人马座比邻星(V645

Centauri) M5.5Ve 11.09[2] 15.53[2] 3,040[6] 14h

29m

43.0s −62°

40′ 46″ 0.768

87(0

29)″[7][8] 4.2421(16) [9]

半人马座

αA(HD

128620) G2V[2] 0.01[2] 4.38[2] 5,790[6] 14h

39m

36.5s −60°

50′ 02″ 0.747

23(1

17)″[7][10] 4.3650(68) 半人马座

αB (HD

128621) K0V[2] 1.34[2] 5.71[2] 5,260[6] 14h

39m

35.1s −60°