{ "bibcode": "2005GCN..3141....1S", "body": "This is a multi-part message in MIME format.\n--------------010903040009000401050606\nContent-Type: multipart/alternative;\n boundary=\"------------020908080103070301090909\"\n\n\n--------------020908080103070301090909\nContent-Type: text/plain; charset=us-ascii; format=flowed\nContent-Transfer-Encoding: 7bit\n\n\n<> V. Simon, R. Hudec (Astronomical Institute AV CR, Ondrejov, Czech\n\nRepublic) and G. Pizzichini, N. Masetti (INAF/IASF Bologna, Italy) report: \n\n<>\nWe have determined the color indices of the optical afterglow (OA) of\n\nGRB050319 in its very early phase from the available data (GCN 3124, \n\n3129). The interpolation method described in Simon et al. (2001, A&A, \n\n377, 450) was used. Since the Swift UVOT magnitudes need a confirmation \n\nof their calibration, we determined the indices separately for UVOT and \n\nground-based observations. The indices of the OA from UVOT are: \n\nt-To=0.0044 d: B-V=0.68; 0.0119: -0.10; 0.0625: 0.85; 0.1968: 0.64, \n\nwhile those of the ground-based observations (GCN 3124) are: t-To(d)=\n\n0.331 d: B-R=0.73; 0.448: 1.12. The typical error of these indices is \n\nabout 0.10 mag. \n\n \n\nThe Galactic reddening E(B-V)=0.011, determined from the maps by \n\nSchlegel et al. (1998, ApJ, 500, 525), is comparable to the errors \n\nof the measurements. \n\n \n\nWe note that the variations in B-V, with a peak at t-To=0.01 days, \n\nare caused by a plateau in B while the V magnitude was already \n\nsteadily decreasing. The last two measurements from UVOT can \n\nsuggest that B-V reached the value roughly consistent with the \n\ntypical one for the ensemble of 23 OAs, defined by Simon et al. \n\n(2001; 2004, AIP Conf. Proc., Vol.727, p.487), not later than at \n\nt-To=0.06 days.\n\n \n\nThe indices of the OA of GRB050319 for t-To > 0.06 days thus appear \n\nto be plausibly consistent with the mean values of the ensemble \n\n(B-V)o=0.45+/-0.15, (B-R)o=0.86+/-0.17. This suggests that the shape \n\nof the spectrum of the afterglow of GRB050319 is similar to the other \n\nafterglows and that its intrinsic reddening (that is inside the host \n\ngalaxy) must be again small (Simon et al. 2001; 2004, AIP Conf. \n\nProc., Vol.727, p.487). Also the redshift of GRB050319 z=3.24 (GCN \n\n3136) suggests that this GRB appears to be another member of the \n\nabove-mentioned ensemble of the OAs with z < 3.5. \n\nThe search for the host galaxy and the determination of its type \n\nare also encouraged. \n\n \n\nThis message may be cited.\n\n \n\n\n--------------020908080103070301090909\nContent-Type: text/html; charset=us-ascii\nContent-Transfer-Encoding: 7bit\n\n\n\n\n \n \n\n\n
\n
\n<> V. Simon, R. Hudec (Astronomical Institute AV CR, Ondrejov,\nCzech \n
Republic) and G. Pizzichini, N. Masetti (INAF/IASF Bologna, Italy) report: \n
\n<>
\nWe have determined the color indices of the optical\nafterglow (OA) of \n
GRB050319 in its very early phase from the available data (GCN 3124,
\n
3129). The interpolation method described in Simon et al. (2001, A&A,
\n
377, 450) was used. Since the Swift UVOT magnitudes need a confirmation
\n
of their calibration, we determined the indices separately for UVOT and
\n
ground-based observations. The indices of the OA from UVOT are:
\n
t-To=0.0044 d: B-V=0.68; 0.0119: -0.10; 0.0625: 0.85; 0.1968: 0.64,
\n
while those of the ground-based observations (GCN 3124) are: t-To(d)=
\n
0.331 d: B-R=0.73; 0.448: 1.12. The typical error of these indices is
\n
about 0.10 mag.
\n
 
\n
The Galactic reddening E(B-V)=0.011, determined from the maps by
\n
Schlegel et al. (1998, ApJ, 500, 525), is comparable to the errors
\n
of the measurements.
\n
 
\n
We note that the variations in B-V, with a peak at t-To=0.01 days,
\n
are caused by a plateau in B while the V magnitude was already
\n
steadily decreasing. The last two measurements from UVOT can
\n
suggest that B-V reached the value roughly consistent with the
\n
typical one for the ensemble of 23 OAs, defined by Simon et al.
\n
(2001; 2004, AIP Conf. Proc., Vol.727, p.487), not later than at
\n
t-To=0.06 days.
\n
\n
The indices of the OA of GRB050319 for t-To > 0.06 days thus appear
\n
to be plausibly consistent with the mean values of the ensemble
\n
(B-V)o=0.45+/-0.15, (B-R)o=0.86+/-0.17. This suggests that the shape
\n
of the spectrum of the afterglow of GRB050319 is similar to the other
\n
afterglows and that its intrinsic reddening (that is inside the host
\n
galaxy) must be again small (Simon et al. 2001; 2004, AIP Conf.
\n
Proc., Vol.727, p.487). Also the redshift of GRB050319 z=3.24 (GCN
\n
3136) suggests that this GRB appears to be another member of the
\n
above-mentioned ensemble of the OAs with z < 3.5.
\n
The search for the host galaxy and the determination of its type
\n
are also encouraged.
\n
 
\n
This message may be cited.
\n
\n\n\n\n--------------020908080103070301090909--\n\n--------------010903040009000401050606\nContent-Type: text/x-vcard; charset=utf-8;\n name=\"rhudec.vcf\"\nContent-Transfer-Encoding: 7bit\nContent-Disposition: attachment;\n filename=\"rhudec.vcf\"\n\nbegin:vcard\nfn:Rene Hudec\nn:Hudec;Rene\norg:Astronomical Institute, CZ-251 65 Ondrejov, Czech Republic;High Energy Astrophysics Group\nadr:;;Observatory Ondrejov;Ondrejov;;CZ-251 65;Czech Republic\nemail;internet:rhudec@asu.cas.cz\ntel;work:00420 323 620128\ntel;fax:00420 323 620263\ntel;home:00420 323 649011\ntel;cell:00420 737 137396\nurl:http://www.asu.cas.cz\nversion:2.1\nend:vcard\n\n\n--------------010903040009000401050606--", "circularId": 3141, "createdOn": 1111747815000, "email": "rhudec@asu.cas.cz", "subject": "GRB050319, color indices", "submitter": "Rene Hudec at AIO ", "eventId": "GRB 050319" }