Abstract
We present the results of a VLT polarimetric monitoring campaign of the GRB 020813 optical afterglow carried out in three nights, from 0.88 to 4.20 days after the gamma-ray event. The mean values of the degree of linear polarization (P) and its position angle (θ) resulting from our campaign are 〈P〉 = 1.18 ± 0.10% and 〈θ〉 = 148.7° ± 23°, after correcting for Galactic interstellar polarization. Our VLT data set is most naturally described by a constant degree of linear polarization and position angle, nonetheless a slow θ evolution cannot be entirely ruled out by our data. The VLT monitoring campaign did not reveal either a significant θ rotation respect to the Keck spectropolarimetric observations performed ∼0.25 days after the GRB (Barth et al. 2003). However, 〈P〉 is a factor of two lower than the polarization degree measured from Keck. Additionally, the VLT polarization data allowed us to construct an accurate V-band light curve. The V-band photometric data revealed a smooth light curve with a break located between the last Keck and our first VLT polarimetric measurement, 0.33 < tbreak.V < 0.88 days after the GRB. The typical magnitude fluctuations of the VLT V-band lightcurve are 0.003 mag, 0.010 mag and 0.016 mag for our three observing nights, respectively. We speculate that the stability of 9 might be related to the smoothness of the light curve.
Original language | English (US) |
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Pages (from-to) | 113-119 |
Number of pages | 7 |
Journal | Astronomy and Astrophysics |
Volume | 422 |
Issue number | 1 |
DOIs | |
State | Published - Jul 2004 |
Externally published | Yes |
Keywords
- Gamma rays: bursts
- Techniques: photometric
- Techniques: polarimetric
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science