First Results of The Konkoly Blazhko Survey II

3.5 MB·English

by  Á. Sódor

**VolumeTitle**
ASPConferenceSeries,Vol.**VolumeNumber**
**Author**
(cid:13)c**CopyrightYear**AstronomicalSocietyofthePacific
FirstResultsofThe KonkolyBlazhko Survey II
2
1 A´.So´dor1,J.Jurcsik1,L.Molna´r1,B.Szeidl1,Zs.Hurta1,G.A´.Bakos2,
0 J.Hartman2,B.Be´ky2,R.W.Noyes2,D.Sasselov2,T.Mazeh4,J.Bartus5,
2 B.Belucz3,G.Hajdu6,Zs.Ko˝va´ri1,E.Kun7,I.Nagy3,K.Posztoba´nyi6,

n P.Smitola3,K.Vida1
a
J 1Konkoly Observatory oftheHungarian AcademyofSciences, P.O.Box67,

6 H-1525Budapest, Hungary
2
2Harvard-Smithsonian CenterforAstrophysics, Cambridge,MA

]
R 3Dept. ofAstronomy, Eo¨tvo¨sUniversity, 1518BudapestPOBox49,Hungary
S
4SchoolofPhysicsandAstronomy,Raymond&BeverlySacklerFacultyof
.
h ExactSciences, TelAvivUniversity, TelAviv69978, Israel
p
- 5Astrophysical Institute Potsdam,AnderSternwarte16,14482Potsdam,
o
Germany
r
t
s 6Visitingastronomer attheKonkoly Observatory oftheHungarian Academyof
a
[ Sciences

1 7University ofSzeged, Dept. ofExp. PhysicsandAstron. Obs.,6720Szeged,
v Do´mte´r9,Hungary
4
7
Abstract.
4
5 ThetwopartsoftheKonkolyBlazhkoSurvey(KBSIandII)areintroduced.The
. mostimportantpreliminaryfindingsofthesecondpartarepresentedincomparisonto
1
the results of the first part. Two interestingcases of verystrongmodulationfrom the
0
KBSIIarealsoshown.
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1
:
v
i
X
1. TheSurvey
r
a
The Konkoly Blazhko Survey (KBS)Iand II aim to collect accurate, extended, multi-
colourlightcurvesofbright,northern,fundamentalmodeRRLyraestarsoftheGalactic
field(So´dor 2007;Jurcsik 2009)inorder to determine the incidence rate of the modu-
lation,tostudythemodulationpropertiesindetailandtostudytemporalchangesinthe
modulation properties.
The first, already finished part of the survey, KBS I, was initiated in 2004. Al-
together, 30 bright, short-period (P < 0.5d) variables were observed with the 60-cm
automatic telescope of the Konkoly Observatory on about 750 nights. A surprisingly
high number of stars (14 out of 30; 47%) were found to show the Blazhko effect. The
mostimportantfindingsofKBSIhasalreadybeensummarizedinJurcsik etal.(2009).
In2009,thesecondpartofthesurvey,KBSII,waslaunchedtoobtainasampleof
longer-periodRRabstars. Ourmaingoalwastocheckwhetherthefrequentoccurrence
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2 So´dor,Jurcsik,Molna´retal.
ofthemodulationfoundintheKBSIsampleisageneralpropertyofRRabstars,orthe
ratio is pulsation-period dependent. In addition to the multicolour observations made
withthetelescopesoftheKonkolyObservatory,Hungarian-madeAutomatedTelescope
Network(HATNet)observations andlight-curve data frompublic data bases (ASAS–
Pojmanski 2002, NSVS–Woz´niaketal. 2004, WASP–Buttersetal. 2010)were also
used to study the whole sample of known RRab stars matching the following criteria:
declination above +10 deg, 2MASS K magnitude brighter than 13.0 mag, pulsation
periodinthe0.55–0.60drange. ThesampleofKBSIIconsistsof124objects.
WhilethemoderatesamplesizeofKBSIallowedadeepstudyofthosevariables,
themuchlarger KBSIIsample wasbetter suited forstatistical analysis ofthemodula-
tionproperties.
2. Light-CurveClassification
Theobjectswereclassifiedintothreegroupsbasedonthecharacterofthelightcurves:
(1)stablelightcurve,(2)modulatedlightcurveor(3)insufficient information.
First,tracesofmodulationweresought. Ifatleastonedatasetofanobjectshowed
definite variations inmaximum brightness, ortheFourier spectrum contained modula-
tion peaks around the pulsation harmonics, the object was classified as modulated. If
no modulation was found, we investigated the data quality to decide wether the light
curve can be classified as stable or the available information was insufficient either to
detectorexcludemodulation.
Aboutone-third (45)oftheinvestigated objectsshowedmodulation, while60ob-
jects had stable light curve. The remaining 19 objects of the sample had insufficient
observational dataforestablishing light-curve stabilityormodulation.
3. ResultsandComparisonwithKBSI
The incidence rate of the modulation in the KBS II sample, disregarding the 19 un-
certain objects, is 43%. The exact ratio depends on which objects have been judged
as uncertain, though. The modulation rate found is only slightly below the value we
have found among the short-period field RR Lyrae stars of the KBS I sample (47%).
This difference can be explained with the lower pulsation and modulation amplitudes
ofthe longer-period RRLyrae stars (Jurcsik etal. 2005). It should beemphasized that
the found incidence rate is a lower limit only, since there could be further Blazhko
stars with modulation amplitudes below the detection limit or the modulation can be
temporal.
In the KBS II sample, the phase relation between the amplitude and phase varia-
tionsofthemaximumlightissuchthat,inmostcases,thelightmaximumtravelsaround
acounterclockwise loop during themodulation. Inotherwords, theearliest-maximum
phase precedes the lowest-amplitude phase. This direction is clockwise only in one
case, counterclockwise at 20 objects and the loop is degenerated or uncertain at the
rest of the Blazhko stars. Similarly, in the KBSI sample, only one object, UZ Virhas
clockwise direction. Thisloop direction isrelated totheasymmetry ofthe modulation
peaks(Szeidl&Jurcsik 2009).
FirstResultsofTheKonkolyBlazhkoSurveyII 3
4. TwoVerySimilarandStrongModulations
TwooftheBlazhkostars intheKBSIIsampleexhibited sostrongmodulation thatthe
pulsation almost disappeared at the lowest-amplitude phase. The light curves of these
two objects, ASAS 212034+1837.2 (HATNet data) and V397 Her (WASP data) are
showninthepanelsofFig.4. Similarlydrasticlight-curvevariationshavealreadybeen
detected in V442 Her (Schmidt&Lee 2000), V445 Lyr (KIC 6186029; Benko˝ etal.
2010)andV18ofM5(Jurcsiketal.2011).
Asignificantdifferenceis,however,thatinV442HerandV18ofM5,noBlazhko
period was found, only long-term pulsation amplitude variations were detected. Con-
trarily, in the two very strongly modulated objects of the KBS II sample, definite
Blazhko periods could be determined (82 d and 52 d for ASAS 212034+1837.2 and
V397Her,respectively).
It is stunning that these two objects, ASAS 212034+1837.2 and V397 Her, be-
haved so similarly, even though they both have complex modulation properties. Both
oftheseobjectswereobservedintwoseasonsandtheverystrongmodulationoccurred
only in one of the seasons. Both stars’ modulation was modestly strong in their re-
spectivefirstobserving seasons(seeupperpanelsoftheobjects). Twoyearslater,both
exhibited almost the strongest possible modulation (bottom panels). These changes in
the modulation could be the result of multiperiodic modulation, where the two modu-
lations caused beating and at certain phases they amplified each other similarly to the
modulation of CZ Lac in 2004 (So´doretal. 2011). Note that, according to Fig. 2 of
Benko˝ etal.(2010),thismightbethecaseinV445Lyr,too.
Such a strong modulation can hardly be explained by non-radial modes superim-
posedonthefundamental radialpulsation mode(Jurcsik etal.2011).
Acknowledgments. ThefinancialsupportoftheHungarianOTKAgrantsT-068626
andK-081421isacknowledged. HATNetoperationshavebeenfundedbyNASAgrants
NNG04GN74G,NNX08AF23GandSAOIR&Dgrants.
References
Benko˝, J. M., Kolenberg, K., Szabo´, R., Kurtz, D. W., Bryson, S., Bregman, J., Still, M.,
Smolec, R., Nuspl, J., Nemec, J. M., Moskalik, P., Kopacki, G., Kolla´th, Z., Guggen-
berger, E., di Criscienzo, M., Christensen-Dalsgaard,J., Kjeldsen, H., Borucki, W. J.,
Koch,D.,Jenkins,J.M.,&vanCleve,J.E.2010,MNRAS,409,1585.1007.3928
Butters, O. W., West, R. G., Anderson, D. R., Collier Cameron, A., Clarkson, W. I., Enoch,
B.,Haswell,C.A.,Hellier,C.,Horne,K.,Joshi,Y.,Kane,S.R.,Lister,T.A.,Maxted,
P.F.L.,Parley,N.,Pollacco,D.,Smalley,B.,Street,R.A.,Todd,I.,Wheatley,P.J.,&
Wilson,D.M.2010,A&A,520,L10.1009.5306
Jurcsik,J.2009,CommunicationsinAsteroseismology,159,53
Jurcsik,J., So´dor,A´., Szeidl,B., Hurta, Z.,Va´radi,M., Posztoba´nyi,K.,Vida, K., Hajdu,G.,
Ko˝va´ri,Z.,Nagy,I.,Molna´r,L.,&Belucz,B.2009,MNRAS,400,1006.0908.1015
Jurcsik,J.,So´dor,A.,&Va´radi,M.2005,InformationBulletinonVariableStars,5666,1
Jurcsik, J., Szeidl, B., Clement, C., Hurta, Z., & Lovas, M. 2011, MNRAS, 411, 1763.
1010.1119
Pojmanski,G.2002,ActaAstronomica,52,397.arXiv:astro-ph/0210283
Schmidt,E.G.,&Lee,K.M.2000,PASP,112,1262
So´dor,A´.2007,AstronomischeNachrichten,328,829.0704.3341
So´dor,A´.,Jurcsik,J.,Szeidl,B.,Va´radi,M.,Henden,A.,Vida,K.,Hurta,Z.,Posztoba´nyi,K.,
De´ka´ny,I.,&Szing,A.2011,MNRAS,411,1585.1009.5498
4 So´dor,Jurcsik,Molna´retal.
ASAS 212034+1837.2 data from HATNet
10.5
2007 2007
magnitude 11.0
11.5
-0.4 -0.2 0.0 0.2 0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8
pulsation phase modulation phase
10.5
2009 2009
magnitude 11.0
11.5
-0.4 -0.2 0.0 0.2 0.4 0.6-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8
pulsation phase modulation phase
V397 Her data from WASP
13.0
2004 2004
magnitude 13.5
14.0
-0.2 0.0 0.2 0.4 0.6 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8
pulsation phase modulation phase
13.0
2006 2006
magnitude 13.5
14.0
-0.2 0.0 0.2 0.4 0.6 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8
pulsation phase modulation phase
Figure1. TheBlazhkoeffectoftwostronglymodulatedtargetsofKBSIIindif-
ferentseasons. Thehighest-andlowest-amplitudeBlazhkophasesaremarkedwith
differentshades/colours. Thestrengthofthemodulationchangedinbothcasessim-
ilarlyduringthenearlytwoyearselapsedbetweentheirtwoobservingseasons.
Szeidl,B.,&Jurcsik,J.2009,CommunicationsinAsteroseismology,160,17.0906.3987
Woz´niak,P.R.,Vestrand,W.T.,Akerlof,C.W.,Balsano,R.,Bloch,J.,Casperson,D.,Fletcher,
S., Gisler, G., Kehoe, R., Kinemuchi, K., Lee, B. C., Marshall, S., McGowan, K. E.,
McKay, T. A., Rykoff, E. S., Smith, D. A., Szymanski, J., & Wren, J. 2004, AJ, 127,
2436.arXiv:astro-ph/0401217