1 / 21

Exploring Radio Afterglows of Gamma-Ray Bursts: Insights from Sydney Institute for Astronomy

Delve into the world of gamma-ray bursts (GRBs) and their radio properties with researchers from the Sydney Institute for Astronomy. Learn about the detection rates of intense bursts of gamma-rays associated with the core collapse of massive stars and the intriguing afterglows of GRBs. Discover how sensitivity limitations influence detection rates and the distribution of faint and bright GRBs. Explore the impact of redshift distribution on detection biases and the power of visibility stacking in measuring population flux. Uncover the existence of two distinct populations of GRBs, shedding light on intrinsic differences between radio bright and faint bursts. This research provides valuable insights into the nature of GRBs and their radio emissions.

yestin
Download Presentation

Exploring Radio Afterglows of Gamma-Ray Bursts: Insights from Sydney Institute for Astronomy

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Radio faint GRB afterglows Sydney Institute for Astronomy (SIfA)/ CAASTRO – The University of Sydney Dr. Paul Hancockwith Bryan Gaensler, Tara Murphy, and DavideBurlon

  2. Overview • Intro to GRBs • Radio properties of GRBs • Radio detection rate

  3. Gamma Ray Bursts • Intense bursts of gamma-rays detected by satellites such as Swift / fermi • Associated with the core collapse of massive stars

  4. GRB afterglows • Long GRBs associated with SNIbc T Totani Piran, 2003, Nature, 422, 268

  5. Only 30% of GRBs are detected at radio frequencies • 304 GRBs observed (VLA+ATCA) • Only 30% have a detected radio afterglow • Detections and upper limits overlap in flux Bright GRB980703A "Typical" GRB980329A Days Since Burst Chandra&Frail 2012

  6. Sensitivity limitations? • Assumption is that detection rate is a function of sensitivity. • Implicitly: • There is a single population of GRBs • Flux (Luminosity) distribution may be broad but is single peaked • Better sensitivity would result in more detections • Thus • The destinction between bright/faint is artificial • the mean flux of the faint GRBs is not far below this artificial divide

  7. Redshift distribution

  8. Parameter distributions No-Redshift Redshift Cumulative Fraction R-band optical flux (μJy) No-Redshift Redshift No-Redshift Redshift Gamma ray Fluence (erg/cm2) 0.3-10 keV X-ray Flux(erg/cm2/s)

  9. Conclusion • The detection rate is NOT being biased by • Differences in redshift distribution • Our ability to measure redshift

  10. The effect of limited sensitivity

  11. Visibility stacking 1x 12 hour observation 12x 1 hour observations SNR ~ 1 SNR ~ 5 For a population of sources, visibility stacking can measure the (weighted) mean flux of the population. Hancock et al., 2011, ApJ ,735, L35

  12. Stacking Results 100-1000 times brighter

  13. What flux would we have expected?

  14. Producing a model flux distribution Luminosity Models => Redshift Distribution => Flux Distribution

  15. Model predictions

  16. Stacked observations Consistent with predictions ~5x fainter than predictions

  17. Two (more) populations of GRBs • Long-soft GRBs are either radio bright or radio faint • There are intrinsic differences between the bright and faint GRBs

  18. A spectral break leads to dark/faint GRBs Greiner et al., 2010, A&A, 526, A30 Piran, 1999, Phys.Rep, 314, 575

More Related