General Coordinates Network

GCN Circulars are now administered through the General Coordinates Network (effective April 17, 2023)

The modernized GCN Circulars experience is part of the new GCN web site, where you can:

This legacy GCN Classic Circulars service has been disabled.

For questions, please contact the GCN Team.

An Invitation To Receive GCN/TAN Notices and Circulars:

There are three major parts to "GCN/TAN": Notices, Circulars, and Reports.
(1) The Notices part distributes GRB/Transient position messages via email or sockets in real-time (LIGO/Virgo, Swift, Fermi, AGILE, INTEGRAL, and others).
(2) The Circulars part distributes prose-style messages about optical/radio/x-ray/gamma-ray follow-up observations via email.

The Notices and Circulars distribution lists are separate because of the different needs of the users and the requirements of the system.
Please read the discusion of those requirements and needs below.

For subscription modifications to GCN Classic Notices sites, please contact the GCN Team.

We encourage all new GCN Notices subscriptions to go through the New GCN. All legacy formats are available by Kafka and email.
The information below is for archival purposes.

GCN Circulars have been migrated to the New GCN, and subscriptions are self service.

When you have decided which (or both) you want to sign up for,
please contact us with the required information for the service(s) you want.
go to here to create a new Notices site (disabled June 2023) and fill in the form.
(And go here (disabled June 2023) to modifiy an existing Notices site configuration; select #2 & enter your sitename.)
Go to the bottom of this page to see about Circulars sign-up.

(1) The Notices Part of GCN/TAN:

We actively invite new sites and instruments to become part of the GCN/TAN network. We encourage any and all band-passes: radio, IR, optical, UV, X- & Gamma-rays, neutrino, and gravity waves also. Many times in the past, we have modified GCN/TAN to accommodate the requirements of new sites and we will continue to do so. No matter what your needs may be, we are sure there is a way that we can accommodate them within the GCN/TAN system.

For those people who have read these GCN/TAN web pages and have a pretty good idea that they want to receive GCN/TAN Notices, the 17 pieces of information listed below are required to create an entry in the "sites.cfg" file and make a site active. And if you haven't read the web pages yet, then these items below provide a hint about how GCN/TAN works, its capabilities and limitations, and what to look for when reading the web pages to make an initial specification for your site's configuration.

THE ITEMS NEEDED FOR EACH NEW SITE (person or robotic/automated system):

1) Site Name:
        Used for identification to quickly and uniquely identify each site.
        This name should be used in all future communications with GCN/TAN OPS.
        Something short (less than 20 characters).
        The parameter name is "site name", but many of the entries are for people or
        other things not necessarily the location 'site" of the activity.
2) Longitude and Latitude of the instrument:
        Needed if the visibility, night-time or some custom filters are used.
        Also needed for the "world map" graphic to show the site's location.
        Decimal degrees is preferred (eg 127.35, -35.51); 127d21m17s,-35d30m19s also accepted.
3) The distribution method?
        The choices are:
        Internet sockets (binary or XML), e-mail (or lmail), and cell/pager (1 long form or
        3 different short forms).  Automated instruments tend to choose the socket method
        because of its speed, and manual instruments tend to opt
        for the e-mail and cell/pager methods.  Cellphone recipients will have
        their destination address (which almost always contains their actual cellphone number)
        translated into an alias so that the number does not appear on the website copy
        of the sites.cfg file.
        For the details.
        And if you choose the full-email format, then for the Swift-based Notices,
        do you want the lightcurve, image, and spectrum attachments (or none).
        And what format do you want them in: FITS, GIF, JPEG, PDF, PostScript?
4) The "address" of the "instrument":
        If you select the sockets method, then we need a "machine.domain".
        If you want e-mail or cell/pager, then "accountname@machine.domain" for each
        person to receive the notices.
5) Sites using the Internet socket method of communication need to choose
        if they want to receive the "socket disconnected notices" (& how often) and
        the "daily socket reports".  For the details.
6) Contact Person:
        A person within the "group" of people involved in the site instrument/operations
        must be given.  This is the point-of-contact person for all communications
        between the group and GCN/TAN. This is also person/address that gets
        the Not-Connected notices if it is a socket-based entry.

7) What Observability filter?
        All, visible, night, custom, etc.  For the details see parts '2a' & '2b'.
8) What intensity threshold?
        This is sometimes used to reject the weaker events whose location uncertainties
        are larger than the site's FOV.
9) Do you want Significance filtering?
        Some of the Notice types have detection significance (units of sigma).
10) Do you want Confidence-level filtering?
        Some of the Notice types have confidence level (units of percent, 0-100%).
11) Do you want Error_Box_Size filtering?
        This will reject notices that have uncertaintites on their locations
        larger that the amount specified (the default is 360.1 degrees, 
        ie there will be no rejection based on error box size as there can be
        no box diameter larger than 360 degrees).  Sites typically choose a value
        which is comparable to the FOV of your instrument  or as large
        as the amount of tiling you are willing to perform.
12) Do you want Time_Delay filtering?
        This will reject notices that have distributions time delays after
        the burst longer than the specified number of hours (the default is 1e14 hours.
        You need to specify the maximum number of hours between the burst/transient
        and when the Notice becomes available for distribution; ie you don't
        anything older than X.X hours.
13) Do you want Trigger_ID filtering?
        This will reject notices that are not identified to be GRBs (e.g. hard
        x-ray transients, known variable sources, negative-curvature bkg intevals, etc).
        It is ~80% accurate, and
        applies only to the Swift-BAT-derived locations.  Currently, there is no Trigger_ID filtering
        for the Fermi Notices.
        The other mission-based sources of locations (e.g. INTEGRAL, IPN, etc)
        are always describing real GRBs.   For the details see part '6'.
14) What other filter funtions?
        In addition the 8 main filtering function above, you can also filter on:
        RA&Dec coordinates, galactic coords, ecliptic coords, Sun angular distance and hour_angle distance,
        Moon angular distance and illumination phase.

15) What source(s) of GRB, X-ray Transient, and/or Gravitational Lensing Notices
        do you want to receive?
        The choices are: Swift, INTEGRAL, Fermi, MAXI, AGILE, MOA, IPN, COUNTERPART, etc.
        For the details or more details see part '1'.
16) What Notice Types within each source do you want?
        For Fermi, there are a few different types, the details.
        For Swift, there are many different types, the details.
        For the details see part '1'.
17) Do you want Test Notices enabled?
        GCN/TAN can generate test notices.  Some sites find these useful
        for testing/exercising their systems & procedures.
        For the details.

Now that you have read the above 17 questions, you can build your configuration request
by selecting #1 on the config_builder_page.

And for those people that are uncertain if GCN/TAN can fill your needs, we encourage you to contact us to discuss your situation. GCN/TAN is a wide and varied system, and some productive accommodation can usually be achieved.

It is also useful for me to know something about your instrument/operation. If you could have the basic numbers describing your system handy during the initial discussion, it would help me to make appropriate suggestions to fine tune the interaction with your system. The basic numbers are the aperture (collecting area), FOV, position resolution, detector type, sensitivity (lim mag, flux, etc), band pass, whether it is an automated or manual system, and response time (instrument response time and human response time). If there is a web-page for your system, then please pass along the URL.

(2) The Circulars Part of GCN/TAN:

This operation is much simplier in its actions and sign-up requirements than the Notices. Circulars are prose-style messages submitted by list-members and then re-distributed to people on the "Circulars" distribution list. There are six pieces of information needed to sign-up for the GCN Circulars:

1) Your full name: John Doe
2) Your institutional and/or project affiliation: NOAO
3) The email address you want to receive the Circulars:
4) Your login account name you will be using to submit: jdoe
5) Your domain from which you will be submitting:
6) Whether you want to receive or not the Circulars -- 1 to receive, 0 not to.

Items 4 & 5 may seem like a duplication of item 3. Item 3 can sometimes be different than from where you will be submitting. Also, some institutions use email servers/forwarders that allow for a generic email address such that email can be delivered to a person no matter how their true account name/machine moves or changes. Items 4 and 5 are used in the validation process for circular submissions. Typically, the domain used in item 5 is reduced down to the institutional level (i.e. no machine name included) to allow for people to submit from more than one machine within their institution. Item 6 allows for people to have more than one entry if they find they will be submitting from more than one account/machine/institution names, but they only want to receive one copy of the outgoing circulars. So only one of their entries in the list would have a "1" value for this flag. For more information on the GCN Circulars.

Go to here to sign up for Circulars.

Return to GCN/TAN homepage.
This file was last modified on 27-Sep-2022.