English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We present an analysis of optical afterglows (OAs) of long GRBs which were mostly discovered by NASA Swift. We used the method of the color indices that uses the commonly available multiband photometry. We show that for most OAs, in the observer frame, these colors, corrected for the reddening inside our Galaxy, display prominent clustering in some color-color diagrams. This clustering shows that we map part of the synchrotron spectrum of OAs with a very similar slope. The color indices of OAs also provide direct information about the environment of GRB. Strong concentration of most colors of OAs shows that the reddening inside their host galaxies must be quite similar and relatively small. Since OAs of the Swift GRBs are mapped in earlier phases than before, any possible color changes caused by the dust must occur in the first minutes after the start of the GRB. We show that although OAs have very similar colors indices, their absolute magnitudes display a very large scatter at the same (t −T0)rest = 0.1 d (i.e. in the rest frame of the GRB). This time corresponds to the early decay of OA. This can suggest that the properties of a fireball do not depend very much on the phenomenon which originated it while the intensities differ considerably.

Long gamma-ray bursts in the Swift era: the color indices of their optical afterglows