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Magnetars Magnetars (IAA-CSIC Granada) Galactic Galactic Neutron Neutron New New Between Between in a in a Link Link (Nature, 405, Pp

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Magnetars Magnetars (IAA-CSIC Granada) Galactic Galactic Neutron Neutron New New Between Between in a in a Link Link (Nature, 405, Pp RapidRapid flaringflaring inin aa newnew GalacticGalactic sourcesource:: aa missingmissing linklink betweenbetween magnetarsmagnetars andand dimdim isolatedisolated neutronneutron starsstars?? (Nature, 405, pp. 506-509) Alberto J. CASTRO-TIRADO (IAA-CSIC Granada) on behalf of a large Collaboration VILLAFRANCA DEL CASTILLO , 30 OCT 2008 CollaborationCollaboration A.J. Castro-Tirado (1), A. de Ugarte Postigo (2,1), J. Gorosabel (1), M. Jelínek (1), T. A. Fatkhullin (3), V. V. Sokolov (3), P. Ferrero (4), D. A. Kann (4), S. Klose (4), D. Sluse (5), M. Bremer (6), J. M. Winters (6), D. Nuernberger (2), D. Pérez-Ramírez (7), M. A. Guerrero (1), J. French (8) , G. Melady (8), L. Hanlon (8), B. McBreen (8), K. Leventis (9), S. Markoff (9), S. Leon (6), A. Kraus (10), F. J. Aceituno (1), R. Cunniffe (1), P. Kubánek (1) S. Vítek (1), S. Schulze (4), A. C. Wilson (11), R. Hudec (12), V. Simon (12), J. M. González-Pérez (13), T. Shahbaz (13), S. Guziy (14), S. B. Pandey (15), L. Pavlenko (16), E. Sonbas (17), S. Trushkin (3), N. Bursov (3), C. Sánchez.-Fernández (18) & L. Sabau-Graziati (19) (1) IAA-CSIC, Camino Bajo de Huétor, 50, E-18008 Granada, Spain (2) ESO, Alonso de Córdova 3107, Vitacura, Santiago, Chile (3) SAO-RAS, Nizhnij Arkhyz, Karachai-Cirkassian Rep., 369167 Russia (4) Thüringer Landessternwarte Tautenburg, Sternwarte 5, D-07778 Tautenburg, Germany (5) Laboratoire d'Astrophysique, EPFL, Observatoire, 1290 Sauverny, Switzerland (6) IRAM, 300 rue de la Piscine, 38406 Saint Martin d'Héres, France (7) Facultad de Ciencias Experimentales, Universidad de Jaén, Campus Las Lagunillas, E-23071 Jaén, Spain (8) School of Physics, University College, Dublin, Ireland (9) Astronomical Institute ‘Anton Pannekoek’, Univ. of Amsterdam, The Netherlands (10) MPI fur Radioastronomie, Bonn, Germany (11) Department of Astronomy, University of Texas, Austin, TX 78712, USA (12) Astronomical Institute of the Czech Academy of Sciences, Ondrejov (13) IAC, Vía Láctea s/n, La Laguna, Tenerife, Spain (14) Nikolaev State University, Nikolskaya 24, 54030 Nikolaev, Ukraine (15) ARIES, NainiTal, India (16) Crimean Astrophysical Observatory, Nauchnyv, Ukraine (17) Univ. of Cukurova, Dep. of Physics, Adana, Turkey (18) ESAC Villafranca del Castillo (Madrid), Spain (19) INTA, Ctra. de Ajalvir km. 4, 28750 Torrejón de Ardoz (Madrid), Spain OutlineOutline IntroductionIntroduction (neutron(neutron stars,stars, pulsars,pulsars, magnetarsmagnetars,, ……)) GRBGRB 070610:070610: aa veryvery unusualunusual XX--ray/optray/opt counterpartcounterpart SWIFTSWIFT J1955+2604:J1955+2604: ExtragalacticExtragalactic oror GalacticGalactic ?? DistanceDistance scalescale ItsIts nature:nature: aa likelylikely magnetarmagnetar (but(but aa UCXRBUCXRB cannotcannot bebe completelycompletely excluded)excluded) Implications:Implications: aa missingmissing linklink inin thethe NSNS familyfamily ?? I.I. IntroductionIntroduction NeutronNeutron stars,stars, pulsars,pulsars, magnetarsmagnetars,, …… NeutronNeutron starstar ““flavoursflavours”” AccretionAccretion--poweredpowered (mainly(mainly XX--rayray binaries)binaries) RotationRotation--poweredpowered (ordinary(ordinary pulsars)pulsars) UltraUltra--strongstrong magneticmagnetic fieldfield--poweredpowered ((magnetarsmagnetars)) RotationRotation andand magneticmagnetic fieldfield poweredpowered (one(one case!)case!) UltraUltra--strongstrong BB--powered:powered: MagnetarsMagnetars First detection on 5 Mar 1979 by Mazets et al. (1979): a tremendous, short burst of soft gamma- rays arising from the SNR N49 in LMC. Dubbed “SGR 0525-65” (“Soft Gamma-ray Repeater”). The localization superimposed to the SNR N49 (Cline et al. 1979) made straightforward its relationship to a NS Another SGRs discovered in the next decades (half a dozen so far) An X-ray burst arising from SGR 1806-20 was detected in 1993, confirming the NS origin (Murakami et al. 1993) Detection of pulsations in SGR 1806-20 (Kouveliotou et al. 1998) proposed a rotating NS with B~5 x 1014 G The magnetar model (Duncan & Thompson 1992) Anomalous X-ray pulsars join magnetars in A magnetic twist gives rise to X-ray 2000’s. emissions (from R. Duncan) II.II. TheThe γγ--rayray burstburst 070610070610 AA veryvery unusualunusual XX--rayray andand opticaloptical counterpartcounterpart (SWIFT(SWIFT J1955+2605)J1955+2605) SwiftSwift detectiondetection ofof aa GRBGRB Detected on 10 June 2007 20:52:26 UT by Swift/BAT as a normal burst, indistinguishable from cosmic GRBs (Pagani et al. GCN 6489) at galactic ccordinates (l , b) = (63.5, -1.0) T90~5s (longer and harder than soft gamma-ray repeater bursts) Photon index 1.76 ± 0.25 GRB 070610 Fluence (2.4 ± 0.4)·10-7 erg/cm2 (Tueller et al. GCN 6491) Swift/XRT detected an X-ray counterpart 3100s later (Pagani et al. GCN 6490) with a column density slightly lower than the Galactic. TheThe opticaloptical counterpartcounterpart Stefanescu et al. (GCN 6492) reported the detection of a variable optical counterpart. de Ugarte Postigo et al. (GCN 6501) confirmed the detection with observations from the 1.5m OSN. D.A. Kann et al. (GCN 6505) suggested a Galactic origin, based on unusual flaring activity and location near the galactic plane: l=63.3º b=-1º Dubbed SWIFT J195509+261406. OurOur datasetdataset BetweenBetween 11 minuteminute andand 11 yearyear afterafter thethe burst:burst: RadioRadio observationsobservations fromfrom RATANRATAN--600600 andand 100m100m EffelsbergEffelsberg MillimetreMillimetre observationsobservations fromfrom PlateauPlateau dede BureBure && IRAMIRAM NIRNIR imagingimaging fromfrom 8.2m8.2m VLTVLT (including(including AO)AO) OpticalOptical datadata fromfrom 1.51.5--mm OSN,OSN, 0.30.3--mm BOOTESBOOTES--2,2, 0.40.4--mm WATCHER,WATCHER, 1.341.34--mm TLS,TLS, 6.06.0--mm BTABTA andand 8.28.2-- mm VLTVLT XX--rayray datadata fromfrom SwiftSwift/XRT/XRT && XMMXMM--NewtonNewton OpticalOptical andand XX--rayray lightlight curvescurves Early light curve / early flares (I) We recorded ~ 40 flare episodes Up to I~14.8, timescales of ~20sec - 7 min Amplitudes up to 1 7 mag OpticalOptical lightlight curvecurve (I)(I) Early light curve / early flares (II) An example of a dense series of VRI Dense series of VRI observations (duration observations (duration ~75 min) (June 10, ~65 min) (June 11, 2007). J1955 was clearly 2007). J1955 was near the detection limit, detected. The I and R data are not quite but peaks of several flares are resolved. simultaneous. Significant fluctuations of the Amplitude of the brightest R band flare is brightness are apparent (~1 mag, timescale > 1 mag(R). Baseline brightness is below ~15 min). Baseline brightness is well- the detection limit. defined both in R and I. OpticalOptical lightlight curvecurve (II)(II) Early light curve / early flares (III) Statistical distribution of R and I magnitudes in the June 11 series. The most abundant faintest magnitude and negative skewness imply that the I observed brightness fluctuations have the form of peaks (spikes) from a well-defined baseline R brightness. The mutual similarity of the statistical distributions of R and I magnitudes in this night series enables to determine the mean color index R-I from the mean mag in each filter. Comparison of the color index R-I from the June 11 series with the color of OAs of GRBs from Simon et al. (2004). Colors of the ensemble are de-reddened for the Galactic extinction and are in the observer frame. The color of J1955 was dereddened by AV = 4 mag, near the lower limit AV=3.6 mag of the suggested range. Further increase of AV leads to the decrease of the color index (arrow). (R-I)0 of J1955 is thus similar to that of the ensemble of OAs and is consistent with the synchrotron emission (e.g. Sari et al. 1998). Thus thermal emission is ruled out. OpticalOptical lightlight curvecurve (III)(III) 2 3 OpticalOptical lightlight curvecurve (IV)(IV) Late flaring AfterAfter thethe thirdthird dayday activityactivity decreasesdecreases AA faintfaint sourcesource waswas stillstill detectabledetectable LastLast flareflare ((nIRnIR)) isis detecteddetected 1111 daysdays afterafter OpticalOptical lightlight curvecurve (V)(V) Light curve- 3 (quiet level) 3 3 OpticalOptical lightlight curvecurve (VI)(VI) Baseline flux evolution The emission between flares 24281211 JuneSeptemberOctoberJune 20072007 2007 2007 slowly decreased until it disappeared. No detectable quiescent counterpart once the flaring emission ceased Limits: H, I > 23 (VLT, SAO, this work) R > 26.5 (Keck, Kasliwal et al. paper, ApJ 2008) I > 24.5 (Keck, Kasliwal et al. paper, ApJ 2008) OpticalOptical spectroscopyspectroscopy…… andand MurphyMurphy’’ss lawlaw Attempted at the 6.0m BTA the 11th and the 12th (bad weather; green) Finally achieved on the 13th when the source was already I~23 (arrow) 6x600s BTA spectra showed not even a detection of continuum III.III. DistanceDistance scalescale TheThe HH columncolumn inin thethe lineline ofof sightsight vsvs thethe absorptionabsorption columncolumn fromfrom thethe XX--rayray spectrumspectrum TheThe redred giantsgiants clumpclump methodmethod DistanceDistance scalescale (I)(I) G. Kanbach & A. Stefanescu DistanceDistance scalescale (II)(II) X-ray (Swift/XRT data): PL +3 21 -2 NH = (7.2 -2) x 10 cm → AV=3.6 – 7.5 mag 21 -2 following E(B-V) = NH/5.9x10 cm H I observations (21 cm line) (Effelsberg), 3 x 3 raster p. 21 -2 → NH I =(8.1±1.2) x 10 cm DistanceDistance scalescale (III)(III) +3 21 -2 X-ray → NH=(7.2 -2) x 10 cm → AV=3.6 – 7.5 mag H I observations 21 -2 → NH I = (8.1±1.2) x 10 cm H2 observations (PdB)
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