The association of a supernova with GRB 0303291,2 strongly supports the collapsar model3 of -ray bursts (GRBs), where a relativistic jet4 forms after 1 the progenitor star collapses. Such jets cannot be spatially resolved because of their cosmological distances. Their existence is conjectured based on breaks in GRB afterglow light curves and the theoretical desire to reduce the GRB energy requirements. Temporal evolution of polarization5,6,7 may provide independent evidence for the jet structure of the relativistic outflow. Small-level polarization ( 1-3%)8−17 has been reported for a few bursts, but the temporal evolution of polarization properties could not be established. Here, we report polarimetric observations of the afterglow of GRB 030329 with high signal-to-noise and high sampling frequency. We establish the polarization light curve, detect sustained polarization at the percent level, and find significant variability. The data imply that the afterglow magnetic field has small coherence length and is mostly random, probably generated by turbulence, in contrast with the high polarization detected in the prompt -rays from GRB 02120618. Our results suggest a different structure and origin of the magnetic field in the prompt vs. afterglow emission regions

Greiner, Jochen

Hartmann, Dieter H.

Klose, Sylvio

Kouveliotou, Chryssa

Palazzi, Eliana

Rau, Arne

Reisch, Klaus

Sari, Re\u27em

Schmid, Hans Martin

Straubmeier, Christian

English

Clemson University: TigerPrints

Clemson UniversityTigerPrintsPublications Physics and AstronomyFall 11-12-2003Evolution of the Polarization of the OpticalAfterglow of the Gamma-ray Burst GRB 030329Dieter H. HartmannDepartment of Physics and Astronomy, Clemson University, hdieter@clemson.eduJochen GreinerMax-Planck-Institut für extraterrestrische Physik, GiessenbachstrasseSylvio KloseThüringer Landessternwarte Tautenburg - Tautenburg, GermanyKlaus ReischUniversitäts-Sternwarte GöttingenHans Martin SchmidInstitut für AstronomieSee next page for additional authorsFollow this and additional works at: https://tigerprints.clemson.edu/physastro_pubsThis Article is brought to you for free and open access by the Physics and Astronomy at TigerPrints. It has been accepted for inclusion in Publicationsby an authorized administrator of TigerPrints. For more information, please contact kokeefe@clemson.edu.Recommended CitationPlease use publisher's recommended citation.AuthorsDieter H. Hartmann, Jochen Greiner, Sylvio Klose, Klaus Reisch, Hans Martin Schmid, Re'em Sari, ChryssaKouveliotou, Arne Rau, Eliana Palazzi, and Christian StraubmeierThis article is available at TigerPrints: https://tigerprints.clemson.edu/physastro_pubs/127arXiv:astro-ph/0311282v1  12 Nov 2003Evolution of the polarization of the opticalafterglow of the gamma-ray burst GRB030329Jochen Greiner∗, Sylvio Klose†, Klaus Reinsch‡, Hans Martin Schmidℓ, Re’em Sari$, Di-eter H. Hartmann¶, Chryssa Kouveliotou§, Arne Rau∗, Eliana Palazzi♦, Christian Straubmeier∗∗,Bringfried Stecklum†, Sergej Zharikov††, Gaghik Tovmassian††, Otto Bärnbantner♯, ChristophRies♯, Emmanuel Jehin¶¶, Arne Henden§§, Anlaug A. Kaas‡‡, Tommy Grav$$, Jens Hjorthℓℓ,Holger Pedersenℓℓ, Ralph A.M.J. Wijers#, A. Kaufer¶¶, Hye-Sook Park♦♦, Grant Williams♯♯,Olaf Reimer##∗Max-Planck-Institut für extraterrestrische Physik, 85741 Garching, Germany†Thüringer Landessternwarte, 07778 Tautenburg, Germany‡Universitäts-Sternwarte Göttingen, 37083 Göttingen, GermanyℓInstitut für Astronomie, ETH Zürich, 8092 Zürich, Switzerland$California Institute of Technology, Theoretical Astrophysics 130-33, Pasadena, CA 91125,USA¶Clemson University, Department of Physics and Astronomy, Clemson, SC 29634, USA§NSSTC, SD-50, 320 Sparkman Drive, Huntsville, AL 35805, USA♦Istituto di Astrofisica Spaziale e Fisica Cosmica, CNR, Sezione di Bologna, 40129 Bologna,Italy∗∗ I. Physikalisches Institut, Universität Köln, 50937 Köln, Germany††Instituto de Astronomia, UNAM, 22860 Ensenada, Mexico♯Wendelstein-Observatorium, Universitätssternwarte, 81679 München, Germany¶¶European Southern Observatory, Alonso de Cordova 3107, Vitacura, Casilla 19001, Santi-ago 19, Chile§§Universities Space Research Association, U.S. Naval Observatory, P.O. Box 1149, Flagstaff,AZ 86002, USA‡‡Nordic Optical Telescope, 38700 Santa Cruz de La Palma, Spain$$University of Oslo, Institute for Theoretical Astrophysics, 0315 Oslo, Norway, and Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USAℓℓAstronomical Observatory, NBIfAFG, University of Copenhagen, 2100 Copenhagen , Den-mark#Astronomical Institute Anton Pannekoek, Kruislaan 403, 1098 SJ Amsterdam, The Nether-lands♦♦Lawrence Livermore National Laboratory, University of California, P.O. Box 808, Liver-more, CA 94551, USA♯♯MMT Observatory, University of Arizona, Tucson, AZ 85721, USA##Theoretische Weltraum-und Astrophysik, Ruhr-Universität Bochum, 44780 Bochum, Ger-manyThe association of a supernova with GRB 0303291,2 strongly supports thecollapsar model3 of γ-ray bursts (GRBs), where a relativistic jet4 forms after1the progenitor star collapses. Such jets cannot be spatially resolved because oftheir cosmological distances. Their existence is conjectured based on breaks inGRB afterglow light curves and the theoretical desire to reduce the GRB energyrequirements. Temporal evolution of polarization5,6,7 may provide independentevidence for the jet structure of the relativistic outflow. Small-level polarization(∼1-3%)8−17 has been reported for a few bursts, but the temporal evolution ofpolarization properties could not be established. Here, we report polarimetricobservations of the afterglow of GRB 030329 with high signal-to-noise and highsampling frequency. We establish the polarization light curve, detect sustainedpolarization at the percent level, and find significant variability. The data im-ply that the afterglow magnetic field has small coherence length and is mostlyrandom, probably generated by turbulence, in contrast with the high polariza-tion detected in the prompt γ-rays from GRB 02120618. Our results suggest adifferent structure and origin of the magnetic field in the prompt vs. afterglowemission regions.GRB 030329 triggered the High Energy Transient Explorer, HETE-II, on March 29, 2003(11:37:14.67 UT)19. The discovery of the burst optical afterglow20,21 was quickly followed bya redshift measurement22 for the burster of z=0.1685 (∼800 Mpc), thus making GRB 030329the second closest long-duration23 GRB ever studied, after GRB 9804253. The proximityof GRB 030329 resulted in very bright prompt and afterglow emission, leading to the best-sampled afterglow to date. Detailed optical spectroscopy revealed an underlying supernova(SN 2003dh)1,2 with an astonishing spectral similarity to SN 1998bw (at z=0.0085, associatedwith GRB 9804253), thus strongly supporting the link of long-duration GRBs with core-collapse supernovae.The apparent brightness of GRB 030329 also afforded a unique opportunity to studythe temporal evolution of polarization in the afterglow phase. Previous single measurementsfound low-level (1-3 %) polarization8−15 in optical afterglows, and the only reports on vari-able polarization16,17 were based on few measurements with different instruments and modestsignal-to-noise. We have overcome the previous sampling limitations with 31 polarimetric ob-servations of the afterglow of GRB 030329 obtained with the same instrumentation (plus fewmore with different instruments) over a time period of 38 days for a total of an unprecedented∼50 hours of observations with an 8m telescope. For the first time we establish a polarizationlight curve for an optical gamma-ray burst afterglow.We performed relative photometry, and derived from each pair of simultaneous measure-ments at orthogonal angles the Stokes parameters U and Q. In order to obtain the intrinsicpolarization of the GRB afterglow, we have to correct for Galactic interstellar polarization(mostly due to dust). We performed imaging polarimetry to derive the polarization parame-ters of seven stars in the field of GRB 030329, and obtained an interstellar (dust) polarizationcorrection of 0.45% at position angle 155deg. Subtraction of the mean foreground polarizationwas performed in the Q/U plane (Qfp=0.0027±0.0013, Ufp=-0.0033±0.0017). Figure 1 showsan R band image of the GRB 030329 field with the polarization ”vectors” superimposed.The temporal evolution of the degree and angle of polarization together with the R bandphotometry is shown in Figure 2. This figure demonstrates the presence of non-zero polar-2ization, Π ∼0.3-2.5 % throughout a 38-day period, with significant variability in degree andangle on time scales down to hours. Further, the spectropolarimetric data of the first threenights as well as the simultaneous R and K band imaging polarimetry during the second nightshow that the relative polarization and the position angle are wavelength independent (withinthe measurement errors of about 0.1 %) over the entire spectral range. These data imply thatpolarization due to dust in the host galaxy of GRB 030329 does not exceed ∼0.3 %. Dustdestruction in the vicinity of the gamma-ray burster due to the strong radiation field wouldresult in a monotonically decreasing polarization degree at constant position angle, whichis not observed during the first days. We therefore conclude that the bulk of the observedvariability is intrinsic to the afterglow.Figure 2 shows that while the polarization properties show substantial variability (forwhich no simple empirical relationship is apparent), the R band flux is a sequence of powerlaws. During each of the power law decay phases the polarization is of order few percent,different from phase to phase, and variable within the phase, but not in tandem with the”bumps and wiggles” in the light curve. We observe a decreasing polarization degree shortlyafter the light curve break at ∼0.4 days (as determined from optical21,24 and X-ray data25,26).Rapid variations of polarization occur ∼1.5 days after the burst, and could be related to theend of the transition period towards a new power law phase starting at ∼1.7 days. Polarizationeventually rises to a level of ∼2%, which remains roughly constant for another two weeks. Atlate time the underlying Type Ic SN 2003dh1,2 increasingly contributes to the total light andprobably also to the observed polarization properties. Asymmetries in this type of supernovacan produce polarization of order 1 %27,28, as we observe towards the end of our campaign.GRB 030329 belongs to a growing group of bursts for which densely monitored afterglowlight curves show significant ”bumps” and ”wiggles” relative to a simple power law decay(most notably GRB 021004 and GRB 011211). These bumps and wiggles complicate theinterpretation of the polarization properties. While the rapid decrease in polarization degreeduring the first night is consistent with the model predictions5,6,7, the position angle changesare not, and thus it remains to be proven whether or not these early polarization datasupport the break at 0.4 days as due to a jet. A connection to theoretical models throughoutthe entire period covered in Fig. 2 is a daunting task. A detailed comparison of our datawith characteristic features of various theoretical models is beyond the scope of this paper,and will be presented elsewhere.In summary, our data constitute the most complete and dense sampling of the polarizationbehaviour of a GRB afterglow to date. For GRB 030329 we conclude that the afterglowpolarization probably did not rise above ∼2.5 % at any time, and that the polarization didnot correlate with the flux. The low level of polarization implies that the components of themagnetic field parallel and perpendicular to the shock do not differ by more than ∼10 %, andsuggests an entangled magnetic field, probably amplified by turbulence behind shocks, ratherthan a pre-existing field. This is in contrast with the high level of polarization detected inthe prompt γ-rays from GRB 02120618 and suggests a different structure and origin of themagnetic field in the prompt vs. afterglow emission regions. Evolving polarization propertiesprovide a unique diagnostic tool for GRB studies, and the extremely complex light curve ofthe optical afterglow of GRB 030329 emphasises that measurements should be carried outwith high sampling frequency.31. Stanek, K.Z., et al. Spectroscopic discovery of the supernova 2003dh associated with GRB030329. Astrophys. J. 591, L17-L20 (2003)2. Hjorth, J., et al. A very energetic supernova associated with the γ-ray burst of 29 March2003. Nature 423, 847-850 (2003)3. Woosley, S.E., Eastman, R.G., Schmidt, B.P. Gamma-ray bursts and type Ic supernovaSN 1998bw. Astrophys. J. 516, 788-796 (1999)4. Mszros, P. Theories of gamma-ray bursts. Ann. Rev. Astron. Astrophys. 40, 137-169(2002)5. Sari, R. Linear polarization and proper motion in the afterglow of beamed gamma-raybursts. Astrophys. J. 524, L43-L46 (1999)6. Gruzinov, A. Strongly polarized optical afterglows of gamma-ray bursts. Astrophys. J.525, L29-L31 (1999)7. Ghisellini, G., Lazzati, D. Polarization light curves and position angle variation of beamedgamma-ray bursts. Mon. Not. R. Astron. Soc. 309, L7-L11 (1999)8. Hjorth, J., et al. Polarimetric constraints on the optical afterglow emission from GRB990123. Science 283, 2073-2075 (1999)9. Wijers, R.A.M.J., et al. Detection of polarization in the afterglow of GRB 990510 withthe ESO Very Large Telescope. Astrophys. J. 523, L33-L36 (1999)10. Covino, S., et al. GRB 990510: linearly polarized radiation from a fireball. Astron.Astrophys. 348, L1-L4 (1999)11. Rol, E., et al. GRB 990712: First indication of polarization variability in a gamma-rayburst afterglow. Astrophys. J. 544, 707-711 (2000)12. Björnsson, G., Hjorth, J., Pedersen, K., Fynbo, J.U. The afterglow of GRB 010222: Acase of continuous energy injection. Astrophys. J. 579, L59-L62 (2002)13. Masetti, N., et al. Optical and near-infrared observations of the GRB 020405 afterglow.Astron. Astrophys. 404, 465-481 (2003)14. Covino, S., et al. Polarization evolution of the GRB 020405 afterglow. Astron. Astrophys.400, L9-L12 (2003)15. Bersier, D., et al. The strongly polarized afterglow of GRB 020405. Astrophys. J. 583,L63-L66 (2003)16. Barth, A., et al. Optical spectropolarimetry of the GRB 020813. Astrophys. J. 584,L47-L51 (2003)417. Rol, E., et al. Variable polarization in the optical afterglow of GRB 021004. Astron.Astrophys. 405, L23-L27 (2003)18. Coburn, W., and Boggs, S.E. Polarization of the prompt (-ray emission from the (-rayburst of 6 December 2002. Nature 423, 415-417 (2003)19. Vanderspek, R., Crew, G., Doty, J., Villasenor, J., Monelly, G. GRB 030329 (=H2652):A long, extremely bright GRB localized by HETE WXM and SCX. GCN Circ. 1997 (2003)20. Price, P.A., et al. The bright optical afterglow of the nearby (-ray burst of 29 March2003. Nature 423, 844-847 (2003)21. Uemura, M., et al. Structure in the early afterglow light curve of the (-ray burst of 29March 2003. Nature 423, 843-844 (2003)22. Greiner, J., et al. Redshift of GRB 030329. GCN Circ. 2020 (2003)23. Kouveliotou, C., et al. Identification of two classes of gamma-ray bursts. Astrophys. J.413, L101-L104 (1993)24. Burenin, R., et al. First hours of the GRB 030329 optical afterglow. Astron. Lett. 29,9, 1-6 (2003)25. Marshall, F.E., Markwardt, C., Swank, J.H. GRB 030329: fading X-ray afterglow withRXTE. GCN Circ. 2052 (2003)26. Tiengo, A., et al. The X-ray afterglow of GRB 030329. Astron. Astrophys., in press;astro-ph/0305564 (2003)27. Wang, L., Howell, D. A., Hflich, P., and Wheeler, J. C. Bipolar supernova explosions.Astrophys. J. 550, 1030-1035 (2001)28. Leonard, D. C., Filippenko, A. V., Chornock, R., and Foley, R. J. Photospheric-phasespectropolarimetry and nebular-phase spectroscopy of the peculiar type Ic supernova 2002ap.Publ. Astron. Soc. Pac. 114, 1333-1348 (2002)AcknowledgementsThis work is primarily based on observations collected at ESO, Chile, with additionaldata obtained at the German-Spanish Astronomical Centre Calar Alto, operated by the Max-Planck-Institute for Astronomy, Heidelberg, jointly with the Spanish National Commissionfor Astronomy, the NOT on La Palma, Canary Islands, and the Observatorio AstronomicoNational, San Pedro, Mexico. We are grateful to the staff at the Paranal, Calar Alto andNOT observatories, in particular A. Aguirre, M. Alises, S. Hubrig, A.O. Jaunsen, C. Ledoux,S. Pedraz, T. Szeifert, L. Vanzi and P. Vreeswijk for obtaining the service mode data reportedhere.5Figure 1: R band image of the field centred on the optical afterglow of GRB 030329. The27 FORS1 (Focal Reducer and Low Dispersion Spectrograph at VLT/Antu) measurementsare shown as ”vectors” where the length is a measure of the polarization degree, and theorientation indicates the position angle. While the afterglow varies in degree as well as angle,the polarization of seven field stars is constant within 0.1% in polarization degree and 1.5degree in position angle throughout the 38 days. Linear polarization was measured from setsof exposures with different retarder plate position angles. Imaging polarimetry was obtainedduring the first four nights (when the afterglow was brighter than 17th mag) from sixteendifferent retarder plate angles, and from eight angles thereafter. Since the FORS1 polarizationoptics allows determination of the degree of polarization to an accuracy of ¡3x10-4 and of thepolarization angle to ∼ 0.2 deg, we consider the above variance of the field stars to representthe systematic error over the 38-day time period. Observations of polarimetric standard starsreproduced their tabulated values within 5%. The FORS1 retarder plate zero point angle of-1.2 degrees was subtracted from the polarization angle. The position angle has a systematicuncertainty of 1.5 deg, which was added in quadrature to the statistical errors.67Figure 2: Evolution of the polarization during the first 38 days. Top and middle panelsshow the polarization degree in percent and the position angle in degrees. The red data pointsare from imaging polarimetry with FORS1/VLT. Spectropolarimetry (blue symbols, 700-800nm range) was performed during the first three nights. The green points were obtained withCAFOS at the 2.2m telescope at Calar Alto on March 30/31. The magenta data point wasobtained with AFOSC at the 2.56m NOT telescope on 2003 April 2. The bottom panelshows the residual R band light curve after subtraction of the contribution of a power lawt-1.64 describing the undisturbed decay during the time interval 0.5-1.2 days after the GRB(i.e., after the early break at 0.4 days), thus leading to a horizontal curve. The symbolscorrespond to data obtained through: the literature (black), the 1m USNO telescope atFlagstaff (blue), the OAN Mexico (cyan), and FORS1/VLT (red). Lines indicate phases ofpower law decay, with the first one from early data21 (not shown). Yellow bars mark re-brightening transitions. Contributions from an underlying supernova (solid curved line) donot become significant until ∼10 days after the GRB.8

Evolution of the Polarization of the Optical Afterglow of the Gamma-ray Burst GRB 030329

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Evolution of the Polarization of the Optical Afterglow of the Gamma-ray Burst GRB 030329

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