Friday 20th of July 2018

1. Introduction

This page a web-interface to a Gamma-Ray Burst (GRB) database feed with the information gathered in the Gamma-Ray Burst Coordinate Network.

2. The database design

The Gamma-Ray Coordinate Network (GCN) system distributes:

  1. locations of GRBs (the Notices) detected by spacecraft (most in real-time while the burst is still bursting and others are that delayed due to telemetry down-link delays).
  2. reports of follow-up observations (the Circulars and the Reports) made by ground-based and space-based optical, radio, x-ray, TeV, and other particle observers.

This web page uses the information from circulars build the grbweb online catalog. A set of PHP scripts, that run every night, download the new Circulars from the GCN archive and extract the information provided by the GRB detector satellites. The extracted parameters are then inserted into a database hosted by a MySQL server. Depending on the detector that sent the Circular it contains different variable information. Moreover the writing style of each Circulars follows a similar pattern and therefore depending on which detector sent the circular a different PHP script is used to parse the information. For each satellite there is a corresponding table in the database with different fields. A description of all main tables in the database can be seen on the following table.

Currently only Circulars are being parsed regularly every day. Depending on the origin of the circular (detector) a row in one of the following tables is created. In addition a more general table is filled. This allows the web-interface to create a summary table of the GRBs. Below are listed all the tables used in the database and the description of each table depending on the detection method. Here you can see graphically the relation of the tables.

Table title r.a. dec.err.t90t1t2αβEpeakγ Emin EmaxF z
J2000 [degree] J2000 [degree] [degree] [s] [s] [s] [keV] [keV][keV][erg s-1]
Fermi LAT
Fermi GMB
Fermi Burst Cat.
Suzaku WAM

3. The grbweb catalog

This grbweb catalog provides the basic information of each GRBs and its expected neutrino spectrum. A detailed description of each of the variables displayed in the catalog is given in the following table:

Section Variable Description
GRB Name GRB name in YYMMDD
UT GRB time [UT]
PositioningRA Right ascension [degree] (J2000)
Decl Declination [degree] (J2000)
ERR Uncertainty [degree]
TimingT100 Duration defined as T2 - T1 [s]
T1 Start time [s]
T2 Stop time [s]
γ-spectrumαγ First spectral index of Band function
βγ Second spectral index of Band function
εγ Energy peak [keV]
fγ Fluence [erg cm-2]
Emin Minimum energy of fluence [keV]
Emax Maximum energy of fluence [keV]
Other z redshift
Light Curve Link to the light curve
Num. Circulars Number of Circulars
ν-spectrumfν Flux at ε1 [GeV-1 cm-2]
ε1 First energy break [PeV]
ε2 Second energy break [PeV]
αν WB spectrum index before ε1
βν WB spectrum index between ε1 and ε2
γν WB spectrum after ε2

WB stands for the Waxman-Bahcall model for neutrinos emission in GRBs. Different satellites might report different values for the same parameter. The web interface takes a decision based on the instrument resolution or accuracy in measuring that specific parameter. The exact ordering depending on the parameter is described in the following table:

Order Timing Positioning Photon spectrum
1 Fermi GBM Swift/UVOT Fermi GBM
2 Konus-Wind Swift/XRT Konus-Wind
3 Suzaku WAM Swift/BAT Suzaku WAM
4 Swift/BAT SuperAgile Swift/BAT
5 Integral Fermi LAT
6 Suzaku WAM Fermi GBM
7 Integral
8 Fermi Burst Catalog

3.1. The neutrino spectra

The grbweb interface will also calculate the predicted neutrino spectrum according to the Waxman-Bahcall model. The calculations followed on the site are described in detail in a paper from Guetta et al. This theory assumes that neutrinos come from p-γ interactions near the break energy of the GRB, making Epeak the second most important parameter, after fluence, for estimating the neutrino flux. This web site uses the gamma-spectrum variables to calculate the neutrino spectrum for each GRB. In case of missing or incomplete information default values are used instead. These defaults values are selected depending on the length of the gamma-ray emission of the GRB. The GCN distinguish between short hard GRBs ( < 2 s) and long soft GRBs (> 2 s) that might have different underlying source:

Long Soft Burst Short Hard Burst X-ray Flash
Fluence10-5 erg cm-210-5 erg cm-210-4 erg cm-2
Epeak200 keV 1000 keV 20 keV
Liso1052 erg1051 erg1051 erg

3.2. Light curves

If the photon light curve information has been measured and is publicly available the PHP scripts will also parse and upload that information into the database. In these cases the online catalog will also provide a link to the light curve for the GRB. This link will open the Light Curve view window where different light curves (as many as they have been measured) are displayed. Currently up to three satellites are searched for light curve measurements: Integral, Swift, and Konus-Wind.

4. How to use the web interface

Just select the period using the pop-up calendar windows or enter a date and click select. A table will be diplayed showing the GRB information for that period. You can obtain further information by clicking on the GRB name.

5. F.A.Q.

This is the frequent asked questions. If you have a question not listed bellow please do not hesitate to send me an email .

Q: Why are the light curves normalized?

A: The reason is just aesthetics; by normalizing the light curves to the maximum point we can guarantee that all light curves are displayed together. However you can download the complete light curve information by clicking "Download lightcurve (txt)" on the same window.

Q: Some of the variables on the web are displayed in bold. What does it means?

A: That means that the value of this parameter has not been measured or reported and therefore only a default values has been selected.

Q: There is an alert symbol next to the GRB name.

A: This alert symbol tells the user that there is some inconsistency in the values from some parameters. There is nothin necessarily wrong, sometimes is only an update of values.