Fast dissemination of GRB afterglow information

1. Fast dissemination of GRB afterglow information Patrizia Ferrero (IASF-BO, OACT & Universita’ di Teramo) 3rd Integral Bart Work Shop Chocerady - November 1-3, 2004

2. Our collaboration Patrizia Ferrero (IASF-BO, OACT & Universita’ di Teramo) Corrado Bartolini, Adriano Guarnieri, Adalberto Piccioni (Universita’ di Bologna) Graziella Pizzichini (IASF-BO) 3rd Integral Bart Work Shop Chocerady - November 1-3, 2004

3. The GRB Coordinates Network (GCN) 3rd Integral Bart Work Shop Chocerady - November 1-3, 2004

4. The GCN was originally developed at NASA/MSFC as BACODINE under Scott Barthelmy to support BATSE positions/identifications • Now at NASA/GSFC, still under Scott Barthelmy, it distributes near real time GRB positions from active satellites as well as reports of follow-up observations by ground based observers • http://gcn.gsfc.nasa.gov/ 3rd Integral Bart Work Shop Chocerady - November 1-3, 2004

5. Why are GCN Circulars so important to us? • They give us information about the OT (optical transient): • localization and position • magnitude • the time of the optical decay essential data to plan other observations. 3rd Integral Bart Work Shop Chocerady - November 1-3, 2004

6. But are GCN data always so complete, exhaustive and precise? The answer is: they aren’t!! We have to remember that they are preliminary data, that it is not mandatory for observers to issue a GCN as soon as they obtain data and that issued data are no longer private, but public. 3rd Integral Bart Work Shop Chocerady - November 1-3, 2004

7. In some cases data are abundant in different filters, in other cases they are relatively scarce. The quality and the quantity of the GCN data are determined by several factors, which could be summarized in this way: 3rd Integral Bart Work Shop Chocerady - November 1-3, 2004

8. OT features • Filters • Number of observations • Calibrations 3rd Integral Bart Work Shop Chocerady - November 1-3, 2004

9. OT features, Filters and Number of observations The situation is different for • GRB with optical afterglow • GRB without optical afterglow 3rd Integral Bart Work Shop Chocerady - November 1-3, 2004

10. OT features, Filters and Number of observations: GRB with OT The kind of optical afterglow would be fundamental for the choice of filter and the amount of observations. different filters (B,V,Rc,Ic) bright OT with a slow decay a lot of observations 3rd Integral Bart Work Shop Chocerady - November 1-3, 2004

11. OT features, Filters and Number of observations: GRB with OT different filters (B,V,Rc,Ic) bright OT with a rapid decay few data Rc and Ic filters faint OT few observations 3rd Integral Bart Work Shop Chocerady - November 1-3, 2004

12. GRB021004: light curves in several filters (data from GCN) 3rd Integral Bart Work Shop Chocerady - November 1-3, 2004

13. GRB030226: light curves in different filters (data from GCN) A rapid decay could explain the lack of more optical data. 3rd Integral Bart Work Shop Chocerady - November 1-3, 2004

14. A lot of multiband data could be useful: • to trace the GRB light curves • to locate on them the point of break • to analyse the color indices and to confirm the studies of them made by Simon et al. 2001. 3rd Integral Bart Work Shop Chocerady - November 1-3, 2004

15. OT features, Filters and Number of observations: GRB without OT In the case of GRB without detected optical afterglow, we have usually upper limits (sometimes in different bands) and few observations. An example..... 3rd Integral Bart Work Shop Chocerady - November 1-3, 2004

16. GRB030416: upper limits in different filters (data from GCN) Here, in spite of the lack of the OT, the observers attempted to give magnitude limits in four filters. 3rd Integral Bart Work Shop Chocerady - November 1-3, 2004

17. Calibrations When a GRB event occurs, all of us are wainting for Henden’s precise photometry to calibrate our data. However, at least at the beginning of data release, we must do without it and choice a system which to refer to. USNOA.2, USNOB.1 or something else? 3rd Integral Bart Work Shop Chocerady - November 1-3, 2004

18. The Guide Star Catalog - II • The GSC2.2 is an all-sky catalog based on 1” resolution scans of the photographic Sky Survey plates, at two epochs and three bandpasses, from the Palomar and UK Schmidt telescopes (DSS). • The GSC2.2 is a joint project of the Space Telescope Science Institute and the Osservatorio Astronomico di Torino. 3rd Integral Bart Work Shop Chocerady - November 1-3, 2004

19. GSC 2.2 vs USNO-B In the future: GSC-2.3 with 997,028,547 objects and mag limit F<20.5 & J<22. 3rd Integral Bart Work Shop Chocerady - November 1-3, 2004

20. GRB021004: Rc light curves with different calibrations (data from GCN) 3rd Integral Bart Work Shop Chocerady - November 1-3, 2004

21. GRB030329: Rc light curves with different calibrations (data from GCN) 3rd Integral Bart Work Shop Chocerady - November 1-3, 2004

22. In other cases it is a matter of bad luck. For example.... 3rd Integral Bart Work Shop Chocerady - November 1-3, 2004

23. GRB030328: light curves of the “orphan” GRB (data from GCN) Although it had about Rc=18, when it was localized, we have few optical data because it was “obscured” by the famous GRB030329. 3rd Integral Bart Work Shop Chocerady - November 1-3, 2004

24. Conclusions • Our conclusions are fairly simple and could be easily anticipated. It would be very helpful and productive, in order to obtain the best set of data: • to have, at least, early estimates of OT magnitudes in several filters, • to converge as soon as possible on the same calibration system or to define some precise rules in order to choice it, • to plan and to share the task of following the OTs with multifilter photometry between different observatories. 3rd Integral Bart Work Shop Chocerady - November 1-3, 2004

25. Thank You for Your Attention !!! 3rd Integral Bart Work Shop Chocerady - November 1-3, 2004