Observations and Analysis of the GK Persei Nova Shell and its "Jet-like" Feature

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by  E. Harvey

Title: willbesetbythepublisher
Editors:willbesetbythepublisher
EASPublicationsSeries,Vol.?,2016
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2 THE GK PERSEI NOVA SHELL AND ITS ‘JET-LIKE’ FEATURE

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a E.Harvey1,M.P.Redman1,P.Boumis2 andS.Akras3
J

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] Abstract. GKPersei(1901,the‘FireworkNebula’)isanoldbutbrightnova
R remnantthatoffersachancetoprobethephysicsandkinematicsofnovashells.
S Thekinematicsinnewandarchivallongslitopticalechellespectrawereanal-
. ysed using the shape software. New imaging from the Aristarchos telescope
h
p continues to track the proper motion, extinction and structural evolution of
- theknots, whichhavebeenobservedintermittentlyoverseveral decades. We
o presentforthefirsttime,kinematicalconstraintsonalargefaint‘jet’feature,
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t that waspreviously detected beyond theshell boundary. Theseobservational
s constraintsallowforthegenerationofmodelsforindividualknots,interactions
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withinknotcomplexes, andthe‘jet’feature. Puttogether,andtakingintoac-
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count dwarf-novaacceleratedwindsemanatingfromthecentralsource, these

1 dataandmodelsgiveadeeperinsightintotheGKPernovaremnantasawhole.
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9 1 Introduction
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GK Per (1901) is a nearby, historic and spectacular source with a proximity of 470pc
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1 Harrisonetal.,2013. The system is one of only two classical novae observed within a
0 planetarynebulatodate,offeringachancetostudytheevolutionofbothclassesofobject.
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Aclassicalnovaeventistheresultofthermonuclearrunawayonthesurfaceofawhite
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dwarfaccretingfrom,typically,amainsequenceoralateGorKtypestarWarner,1995.
:
v The accreted shell is ejected, at velocities that range from 5x102 to a few x103 km s−1
i
X Bodeetal.,2008. Dwarfnovae,whicharealsoexhibitedbyGKPer,arecausedbyanin-
stabilityintheaccretiondisksurroundingthewhitedwarfstarOsaki1996. Theseevents
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a accelerate winds to the order of 1-6x103 km s−1, see Kafkaetal.,2004 and references
therein. It is unknown if their ejection is spherically uniform or intrinsically bipolar
Lloydetal.,1997, Porteretal.,1998. The common envelope phase is thought to play
a majorrole in the shapingof novaremnantsand planetarynebulae alike. Slower nova
1CentreforAstronomy,SchoolofPhysics,NationalUniversityofIrelandGalway,Galway,Ireland
2NationalObservatoryAthens,IAASARS,I.Metara&V.Pavlou,Penteli,GR-15236Athens,Greece
3Observato´riodoValongo,UniversidadeFederaldoRiodeJaneiro,LadeiraPedroAntonio4320080-090
RiodeJaneiro,Brazil
(cid:13)c EDPSciences2016
DOI:(willbeinsertedlater)
2 Title: willbesetbythepublisher
eventsarebelievedtohavestrongerdeviationsfromsphericalsymmetrye.g. V1280Sco
Chesneauetal.,2012 when comparedto their moreenergeticcounterparts. The system
exhibitsapronouncedstreamofemissiontotheNEofthenovashellthatisreminiscent
ofajetbutwhoseoriginhasnotbeensettled. Newandarchivalobservationsareusedto
explorethestructureandkinematicsoftheGKPernovashell.
2 Kinematicsoftheshell,knotsand‘jet’
Using the Aristarchos telescope in Greece, new imaging was collected of GK Per in
September 2014. The observations consisted of three narrow band filters (Hα, [N ii]
and[Oiii]),with1800sexposuresineachfilter. ArchivaldataofLiimetsetal.,2012was
used and of Lawrenceetal.,1995, Sharaetal.,2012. The imaging was reduced using
iraf. Tobuildafullerviewoftheremnantandexaminethe‘jet-like’feature,Manchester
EchelleSpectrometer(MES)data were obtainedatthe San PedroMa´rtirobservatoryin
Mexico. Position-Velocity(P-V) arrayswere generated. The knotandshell P-V arrays
were simulated using the morpho-kinematicmodelling code shape Steffenetal.,20061.
AfulldiscussioncanbefoundinHarveyetal. (2016inprep).
Shellkinematics: shapemodelingdemonstratesthattheshellmostprobablyconsists
ofanoblateelongatedring-likeequatorialstructure(PA∼120◦ andinc∼54◦)withpolar
over-densities (Fig. 1). The ‘boxy’ nature of the nebula has long been observed e.g.
Seaquistetal.,1989. The position angle derived of the old nova shell fits that of the
‘fossil’ bipolar planetary nebula and the inclination to that of the binary. We find that
the‘polarcaps’haveasystematicallylowerexpansionvelocitythantherestoftheshell.
In the IRSA archives the longer wavelength WISE Wrightetal.,2010 bands show an
abundanceofmaterialalongthesepolarregions,potentiallyhavingasignificanteffecton
theirvelocitystructureevolution.
Knot Characteristics: In a clump-wind interaction their relative velocities must be
considered,asitisbelievedtobethemainmechanismintheshapingoftheclumps. Un-
dermoreuniformconditions,sub-sonicclumpshavelongtailsandtheirsupersoniccoun-
terparts display short-stubby tails Pittardetal. 2005. There are a variety of tail shapes
presentinGKPersuggestingdiverselocalflowconditions. Thesinusoidalnatureofthe
tailsoftheknotsalongtheouteredgeoftheshellareevidentinthe1997Hubbleimages
inSharaetal.,2012. Thesewavy tailscouldbeattributedtoshapingbythedwarfnova
winds,whichcanthusbefoundtohaveavelocityof∼4400kms−1.Bianchinietal.,1986
gaveavelocityestimateofGKPer’sdwarfnovawindsofafew1000kms−1.
Kinematics of the jet-like feature: Previously there have been several theories to
theoriginofthisfeature,Bodeetal.,2003,Anupamaetal.,2005,Sharaetal.,2012,first
mentionedinAnupamaetal.,1993. Light-echocontoursoverIRASimageryhintedthat
it predated the nova shell Bodeetal.,2003. As our new kinematic data suggests a low
velocity (<17 km s−1 with a Gaussian FHWM rangingfrom 30-40 km s−1) we suggest
that the feature may be an illuminated part of the waist of the fossil planetary nebula.
Thiswouldalsoexplainthecurvatureandspreadingoutofthefeature. Thereisaslight
1Afulldescriptionofshapecanbefoundathttp://bufadora.astrosen.unam.mx/shape/
Harveyetal.:GKPerKinematics... 3
Fig. 1: Panel(a) showsthe red-blueDopplerdistributionasderivedfromP-Varraysas
well as channelmaps overlaid on an image from the Mayall telescope, north is up and
eastistotheleft. Panel(b)showstheobservedradialvelocitiesof148knotsdependant
ontheir‘y’position,i.e. fromthenorthtosouthofthenebula,wherethegreyscaleisthe
equivalentforthemodelcreatedinshape. Panel(c)isthesameasthemiddlepanelexcept
thepositionalargumentsarefromtheeasttowest.
Fig.2:Examplesofknotsprogressingovertime(2007-2014)andtheircorrespondingP-V
arrayandmorpho-kinematicshapemodel.AdditionalepochP-Vinformationisincluded,
the knots here are along an axis of symmetry of the nova shell. The ALFOSC P-Vs
correspond to the 2007 NOT image and the MES P-Vs correspond to the Aristarchos
observationsepoch.
augmentationinbrightnessofthislineintheHαand[Oiii]5007Ålinescorrespondingto
thelocationofinteractionwithpre-existingmaterialseeninradioandX-rayobservations
Anupamaetal.,2005,Balman,2005,Takeietal.,2015.
3 Discussion&Questions
One of the main findings from Liimetsetal.,2012was there is no significantdecelera-
tionoftheknotsintheSWquadrantofthenovashell,thoughithadbeenlongbelieved
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that the shell had been experiencing a stronger interaction with circumbinary material
in this quadrant Duerbecketal.,1987. The barrel with polar over-densities structure
presented here, as well as the basic bullet crushing time calculation support their find-
ing. Takeietal.,2015 indicates the system is moving through less dense material than
during the time of the observations of Balman,2005. The derived morphology is de-
cidedly oblate, in contrast to the shapes of other nova shells e.g. Ribeiroetal.,2009,
Munarietal.,2010. Lloydetal.,1997used a 2.5D codeto investigateremnantshaping
for a variety of speed classes and produced rings, blobs and caps as expected but also
created oblate remnants. Later Porteretal.,1998 included the effects of a rotating ac-
creted envelope,surprisinglythe first panelin their Fig. 2 baresquite a resemblanceto
themorphologyderivedhere.
SOKER:HaveyoulookedatthejetsinNGC40thatareperpendiculartotheshell?
HARVEY:Interestingbutno. Iwillinvestigate.
HAMAGUCHI:DoesyourmodelfittheX-raymorphology?
HARVEY:Itsuggeststhattheflattenedshellisanintrinsicfeatureandissupportedby
thenon-perpendicularpropermotionofthesystemfrom1917-1993,derivedbyBode.
DEMARCO:Ontheneonoverabundance,couldGKPerbeabornagainABGstar?
HARVEY:In photoionisationsimulations, we conductedusing Cloudy, a significant
initialoverabundanceofneonwasrequired.However,thestellarspectrumisnotdeficient
inhydrogennorenrichedinhelium,suggestinganovaoriginismorelikely.
E.HarveywishestoacknowledgethesupportoftheIrishResearchCouncilforprovidingfundingforthisproject
undertheirpostgraduateresearchscheme. TheauthorsgreatlybenefittedfromdiscussionswithDr. Wolfgang
Steffen,Prof.JohnMeaburn,Dr.MyfanwyLlyod,Dr.TomilsavJurkicandDr.ValerioRibeiro,amongstothers.
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