GCN News and Events

End of Swift Science Operations, CHIME Notices Unavailable During Upgrade

The GCN Team announces:

• End of Swift Science Operations
• CHIME Notices Unavailable During Upgrade

End of Swift Science Operations

NASA's Neil Gehrels Swift Observatory has reached a sufficiently low altitude that science observations are no longer feasible. Final observations were obtained on Tuesday, October 20, after which the spacecraft was commanded to prepare for atmospheric re-entry, which is anticipated sometime next week. See the Press Release for more details.

While science operations have ceased, the team still has very critical work to do during our “close-out” phase, developing and archiving final science catalogs and data sets. In addition, we are planning one final community General Investigator (GI) call for archival analysis of Swift data (deadline January 28, 2027).

CHIME Notices Unavailable During Upgrade

The CHIME/FRB GCN alerts service is offline starting Sunday, October 18th at 1700 UTC, due to a scheduled hardware upgrade of CHIME. The expected return of alerts is January 2027.

JSON Notices via Email, Advisory for Kafka Cron Jobs, Update Your Submitter Profile, GCN is Hiring

The GCN Team announces:

• JSON-Format Notices Now Available via Email
• Advisory for Kafka Cron Jobs
• Update your Circular Submitter Profile
• GCN is Hiring a Full-Stack Web Developer

JSON-Format Notices Now Available via Email

You can now receive any public JSON Notice types via email. To sign up for Notices via email in JSON or any legacy format, visit the Email Notifications page. Note that base 64 encoded attachments (e.g. HEALPix localization maps) are automatically stripped out of emails, but remain available via Kafka. Nearly all new Notice types added in the last couple of years are JSON format, and many of the legacy producers have started also producing JSON Notices or are in the process of migrating. Visit the Missions page to see which Notice types are available in legacy or JSON formats.

Advisory for Kafka Cron Jobs

Our Kafka client setup code sample is designed to be used as part of a long or indefinitely running program. If you leave it running, our Kafka client code will promptly provide you with the latest received messages, and will recover automatically from transient failures like network connectivity problems or temporary broker outages.

Please do not launch short-lived, single-shot, high-frequency (>hourly) clients (e.g., clients that consume or produce zero or one messages, and then halt). Each time that you launch a new client, we are billed a tiny amount which can add up significantly. Due to how our authentication works, launching many short-lived clients can increase our operating costs (see Code of Conduct). Please be responsible and don't launch clients periodically in cron jobs.

Update Your Circular Submitter Profile

The Circular submitter field includes your email address, full name, and affiliation. If you don't fill out your profile, it will only contain your email address. Login and check your profile today.

GCN is Hiring a Full-Stack Web Developer

The GCN team is hiring a full-stack web developer. Please share the GCN developer advertisement with anyone you think might be interested.

LVK Notices Exclusively Available in JSON over Kafka, Updated CHIME Notices, and Schema v7.2.3

The GCN Team announces updates to LVK and CHIME Notices and a schema release.

• LVK Notices Exclusively Available in JSON over Kafka
• Updated CHIME Notices
• Schema v7.2.3

LVK Notices Exclusively Available in JSON over Kafka

As of July 8, 2026, the LIGO-Virgo-KAGRA (LVK) collaboration has ceased sending gravitational wave alerts in the VOEvent format to GCN Classic. The LVK VOEvent alerts were converted to all other GCN Classic formats and distribution methods (text via email and binary via socket connection). As a result, this change also disables all legacy LVK formats (text, binary, VOEvent) distributed over Kafka and email.

GCN now distributes LVK Notices exclusively as JSON over Kafka. The LVK Public Alerts User Guide has been updated to provide information on the alert system that will be deployed in the next observation run (IR1) that is expected to start in late 2026.

To receive GCN Notices on LVK during IR1, please subscribe to JSON-format Notices on the Kafka topic igwn.gwalert. At this time, these Notices are only available via Kafka, not email.

Updated CHIME Notices

CHIME is now distributing retractions of their FRB Notices on the topic gcn.notices.chime.frb, and has updated the example added in Schema v7.2.1.

Schema v7.2.3

GCN Schema v7.2.3 is available with recent changes including updated Notice examples (Release Notes).

New JavaScript client v1.0.0

We have released version 1.0.0 of the official JavaScript client for GCN Kafka. We migrated the client backend from kafkajs to @confluentinc/kafka-javascript. They have the same interface, but the latter is better maintained and shares the same underlying Kafka client library as the Python bindings.

Aside from more reliable operation, the only change for users should be that you now have to explicitly call connect(), like this:

import { Kafka } from 'gcn-kafka'
const kafka = new Kafka({
  client_id: 'fill me in',
  client_secret: 'fill me in',
})

const consumer = kafka.consumer()
await consumer.connect() // <-- NOW REQUIRED IN VERSION 1.0.0
await consumer.subscribe({
  topics: [
    'gcn.classic.text.FERMI_GBM_FIN_POS',
    'gcn.classic.text.LVC_INITIAL',
  ],
})

New MAXI Notices and Schema v7.2.0

The GCN Team is pleased to announce new Notice Types and a schema release.

• MAXI X-ray Known and Unknown Transients Notices
• Schema v7.2.0

MAXI Known and Unknown X-ray Transient Notices

The MAXI Team and the GCN Team are pleased to announce the availability of MAXI Notices via the new GCN in JSON format. MAXI is a wide-field X-ray telescope designed to perform an all-sky survey onboard the ISS.

MAXI provides Notices for both known and unknown source detections by Gas Slit Camera (GSC). The known source Notice is used when the detected event is associated with a known X-ray source or cataloged object. The unknown source Notice is used when the detected event is not immediately associated with a known source and is reported as a new or unidentified transient candidate. Depending on the available localization information, an unknown source Notice may report no position uncertainty, a circular uncertainty region, an elliptical uncertainty region, or rectangular error-region corners.

Both Notice types provide basic alert metadata, event timing, sky position, flux information, and detection information.

MAXI notices are published on the GCN Kafka topics gcn.notices.maxi.gsc.known and gcn.notices.maxi.gsc.unknown.

See the MAXI mission page for a more extensive description of the information provided in these new notices.

Schema v7.2.0

GCN Schema v7.2.0 is available with recent changes including new Notice types (Release Notes).

New BOOM Notices and Schema v7.0.0

The GCN Team is pleased to announce new Notice Types and a schema release.

• BOOM Cross-Correlated Optical Transients Notices
• Schema v7.0.0

BOOM Cross-Correlated Optical Transient Notices

The Burst & Outburst Observations Monitor (BOOM)/Babamul Team and the GCN Team are pleased to announce the availability of a new notice type via the new GCN in JSON format. BOOM provides real-time brokering, archival context, and coordination tools that enable rapid identification, vetting, and follow-up of astrophysical transients. BOOM is the software stack operating to enable a multi-survey alert broker and data archive (Babamul) that ingests and combines alerts from the Zwicky Transient Facility (ZTF) and the Vera C. Rubin Observatory alert stream.

BOOM is contributing a GCN Notices stream, where cross-matches from the BOOM fast transient stream (which analyzes ZTF and LSST alert streams) are checked for (i) gravitational-wave alert candidates consistent with a binary neutron star merger or neutron star-black hole merger and (ii) gamma-ray bursts detected by Fermi, SVOM, and Swift. This enables rapid cross-identification of events across experiments and observatories, enhancing situational awareness and time-critical response for the broader transient astronomy community. Alert includes localization, photometry, cross-matches with other GCN Notices, and classification scores from machine-learning models.

BOOM notices are published on the GCN Kafka topic gcn.notices.boom.alert.

See the BOOM mission page for a more extensive description of the information provided in these new notices.

Schema v7.0.0

GCN Schema v7.0.0 is available with recent changes including new Notice types and a modified and generalized Spectral core schema (Release Notes).

Retirement of GCN Classic VOEvent Brokers

As initially announced in 2025, we are planning to retire the GCN Classic VOEvent brokers on April 6, 2026. This impacts users who utilize the VOEvent Transfer Protocol (VTP) to receive VOEvent-format GCN Classic Notices. VOEvent-format Notices remain available via Kafka and email, and we recommend users migrate from VTP to Kafka.

Passing of Scott Barthelmy, GCN Founder

With heavy hearts, we report that our colleague and mentor Scott Barthelmy passed away on February 25, 2026. Scott was the founder, architect, and tireless maintainer of GCN from its inception in 1993 until his retirement (history of GCN). Scott was supportive of the development of the new GCN, and we have always aimed to honor his legacy and service to our community. As PI of the Swift-BAT and Swift Project Scientist, he had exceptional impacts on our field.

New CHIME, DSA-110, and IceCube Notices and Schema v6.1.1

The GCN Team is pleased to announce new Notice Types and a schema release.

• CHIME Fast Radio Burst Notices
• DSA-110 Fast Radio Burst Notices
• IceCube Gold/Bronze Notices
• Schema v6.1.1

CHIME Fast Radio Burst Notices

The CHIME Team and the GCN Team are pleased to announce the availability of a new CHIME Fast Radio Burst (FRB) notice type via the new GCN in JSON format. We welcome this new transient type to the GCN community and encourage follow-up observations. These notices can be streamed via Kafka. They are not available via GCN Classic.

The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a transit radio telescope located in Penticton, BC, Canada. It consists of 4 semi-cylindrical reflectors, each with 2000 square meters of collecting area and 256 dual-polarization antennas. The telescope observes between 400 MHz and 800 MHz and covers an instantaneous field of view of ~200 square degrees. CHIME houses several electronic backends, which are tailored for specific scientific goals, such as generating cosmological maps of hydrogen density, detecting Fast Radio Bursts, and observing and timing pulsars. In particular, the FRB backend operates at ~1 ms time resolution and ~ 0.4 MHz frequency resolution.

The new CHIME notices provide FRB detection details including ~arcminute localization with a latency of ~1 minute. The detection rate is ~600 per year. Notices will be distributed on the Kafka topic:
gcn.notices.chime.frb

A more extensive description of the information provided in these new notices is available at https://gcn.nasa.gov/missions/chime.

DSA-110 Fast Radio Burst Notices

The DSA-110 Team and the GCN Team are pleased to announce the availability of DSA-110 notice types via the new GCN in JSON format. These notices can be streamed via Kafka.

The Deep Synoptic Array-110 (DSA-110) is a radio interferometer purpose-built for fast radio burst (FRB) detection and direct localization. The array is located at the Owens Valley Radio Observatory (OVRO) comprised of 96 4.65-m dishes that continuously survey for FRBs at frequencies between 1280 to 1530 MHz. Over a three-year science program, the DSA-110 will deliver a sample of more than 300 FRBs, each localized to regions ~1 arcminute radius within 1 minute of detection. This is made possible by a suite of novel instrumentation, including precisely engineered antennas, ultra-low noise ambient-temperature receivers, and a powerful real-time, autonomous data-analysis system.

DSA-110 notices provide FRB detection and localization distributed on the topic gcn.notices.dsa110.frb.

See the DSA-110 mission page for a more extensive description of the information provided in these new notices.

IceCube Gold/Bronze Notices

The IceCube Team and the GCN Team are pleased to announce the availability of a new IceCube Notice type via the new GCN in JSON format for Gold/Bronze Track alerts. These notices can be streamed via Kafka. The information included in the JSON-format Notices largely overlaps with that in GCN Classic with the addition of a URL of multi-order probability maps. AMON_ICECUBE_GOLD and AMON_ICECUBE_BRONZE notices remain available via GCN Classic and GCN Classic over Kafka.

IceCube is a cubic-kilometer Cherenkov particle detector deployed in the Antarctic ice beneath the Amundsen-Scott South Pole Station. IceCube detects neutrinos by observing the light produced by relativistic charged particles created by neutrino interactions in or near the instrumented volume of ice.

Notice Topic: new Gold/Bronze Notices provide high-energy (TeV-PeV) track-like alerts with radius angular resolution. Events are classified into Gold and Bronze based on their likelihood of being astrophysical. Two GCN Notices are sent for each event - one corresponding to the preliminary reconstruction and one corresponding to the revised reconstruction. Gold and Bronze events occur at a rate of 10 and 16 per year, respectively, with a latency of 0.5-1 minute from detection. These new alerts are distributed via GCN Kafka on the topic gcn.notices.icecube.gold_bronze_track_alerts.

The IceCube documentation has been extensively updated. It now includes details on the new information released with the updated schema, as well as explanations of the quantities listed in the FITS file headers for the multi-order probability maps.

Schema v6.1.1

GCN Schema v6.1.1 is available with recent changes including new Notice types (Release Notes).

Super-Kamiokande JSON Notices and Schema v4.5.0

New Super-Kamiokande JSON Notices

The Super-Kamiokande Team and the GCN team are pleased to announce the availability of Super-Kamiokande notice types via the new GCN in JSON format. These notices can be streamed via Kafka. SK_SN notices remain available via GCN Classic and GCN Classic over Kafka. The information included in the JSON-format Notices largely overlaps with that in GCN Classic with some additional parameters: the number of detected inverse beta decay (IBD) events, the analysis pipeline used (snwatch or wit), and the type of processed sample (full or partial) used for event detection.

Super-Kamiokande Summary: Also known as Super-K or SK, Super-Kamiokande experiment was built and has been operated with funding from the Japanese Ministry of Education, Science, Sports and Culture, and the U.S. Department of Energy. Designed to understand the nature of neutrinos, Super-K is a leading detector in the search for MeV neutrino detections of core-collapse supernovae.

Notice topic: new Super-Kamiokande notices provide core-collapse supernova detection and localization as well regular monthly test alerts distributed on the topic gcn.notice.superk.sn_alert.

See the SKSN mission page for a more extensive description of the information provided in these new notices.

Schema v4.5.0

GCN Schema v4.5.0 is available with recent changes including the Super-K schema (Release Notes).

Client Credential Expiration Policy

For security purposes, we will disable client credentials that you have not used to connect to a Kafka broker for the past 30 days. We will email you reminders 9 days before client credentials will expire. Once disabled, a client credential cannot be used again. To prevent a credential from expiring and being disabled, simply use it to connect to a Kafka broker. You may create new client credentials at any time. To review, create, delete, and manage your client credentials, see your account client credential settings.

Browse Circulars by Event, Advanced Search, Sample Codes, Schema Release

The GCN Team is pleased to announce new features, documentation, and a schema release.

• Browse Circulars by Event
• Circulars Advanced Search
• Mission Notices Table
• Notices Sample Code
• Apache Spark Kafka Client
• Schema v4.4.0

Browse Circulars by Event

By popular demand, you can now view Circulars grouped by astronomical event. In the Circulars archive, you can now toggle between two view modes:

Circulars View

• View Circulars sorted inversely by Circular ID.
• Use the search bar to search for text strings (e.g. 250101A), Circulars numbers (e.g. 12345), or use Advanced Search.

Events View

• View a list of astronomical events (e.g. GRB 250101A, LIGO/Virgo/KAGRA S250331o, EP250101a), expand to show all Circulars associated with that event, or tap the event name to see all related Circulars in sequence (similar to the GCN Classic Circulars archive).
• Use the search bar to search by event name (e.g. GRB 250404A).
• The GCN Team manually associates events with multiple names (e.g. GRB 250404A, EP250404a) into event groups. You can view all Circulars associated with any member of an event group by selecting that event in the event view. You can also search for an event by any event name that group. If you would like to suggest additional event names that should be in the same event group, please contact the GCN Team.

See additional documentation on event view, event names, and event groups.

Circulars Advanced Search

The Circulars archive now allows users to search for keywords by Subject, Body, and Submitter. Select "Advanced Search" to view and copy example syntax. See documentation for more details, examples, and compound query logic.

Mission Notices Table

The Missions page now contains a table listing the status of all current, past, and upcoming Notices producers. You can learn about the formats and distribution mechanisms that are available for every Notice type, including the transitions to GCN Kafka. The table provides mission-specific links to signup for Notices over email and the Kafka start streaming guide.

Notices Sample Code

Sample code serves as a starting point for consumers of GCN Notices for functions including consuming Kafka messages, parsing plain text, VOEvent XML, and JSON format notices, and interacting with HEALPix maps. We have also included producer sample code for encoding embedded data (e.g. HEALPix maps). The GCN Team welcomes contributions of additional sample code that might be of use to our community.

Apache Spark Kafka client

We added Kafka client sample code for Apache Spark. Apache Spark is a multi-language engine for executing data engineering, data science, and machine learning on single-node machines or clusters.

Schema v4.4.1

GCN Schema v4.4.1 is available with recent changes including the generic high-energy neutrino and fast radio burst schema (Release Notes).

Circulars over Kafka Event Name Backfill

In preparation for new search and sort features in the GCN Circulars archive, the GCN team will be backfilling the automatically assigned event name (e.g. "eventId": "GRB 250331C") derived from each GCN Circular subject. Event names have been included in all JSON versions of Circulars starting with GCN Circular 37912. The backfill of all prior Circulars will result in the following behavior that may impact some users:

• The entire archive of ~40k Circulars will be distributed over Kafka with the new event names.
• Revised Circulars will not be redistributed over email.

The event name backfill will be executed on April 7, 2025.

End of INTEGRAL Operations

Beginning March 4, 2025 at 12:08:04 UT, data from the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) will no longer be transmitted to the INTEGRAL Science Data Centre (ISDC), due to the end of scientific operations, more than 22 years after its launch. As a consequence, the INTEGRAL Burst Alert System (IBAS) will be discontinued and GCN Notices will no longer be distributed. The full archive of INTEGRAL GCN Notices is available at https://gcn.gsfc.nasa.gov/integral.html.

The IBAS team thank the scientific community for the continuous support. The GCN team thank INTEGRAL for being an important contributor to GCN over the last 22 years.

The mission pages for GCN Notice producers that are no longer operational have been moved to a submenu for archived missions, including AGILE, BurstCube, and INTEGRAL.

New SVOM Notices, Retirement of VOEvent Brokers

SVOM VOEvent Notices Available Over Kafka

The SVOM Team and the GCN team are pleased to announce the availability of SVOM notice types via the new GCN in VOEvent format. These notices can be streamed via Kafka. They are not available via GCN Classic. The SVOM Team plans to add JSON format notices at a later date.

SVOM Mission Summary: The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a French-Chinese mission, result of a collaboration between the two national space agencies, China National Space Administration (CNSA) and Centre national d'études spatiales (CNES). SVOM mission is dedicated to the study of the most powerful transient phenomena, with a particular emphasis on gamma-ray bursts (GRBs). The SVOM spacecraft carries four multi-wavelength instruments: ECLAIRs, Gamma Ray burst Monitor (GRM), Microchannel X-ray Telescope (MXT) and Visible Telescope (VT).

Notice topics: new SVOM notices provide GRB detection and follow-up observation details. Each of the four instruments has its own dedicated topic to stream notices with their related information, see table below:

• gcn.notices.svom.voevent.grm
• gcn.notices.svom.voevent.eclairs
• gcn.notices.svom.voevent.mxt
• gcn.notices.svom.voevent.vt

A more extensive description of the information provided in these new notices is available at https://gcn.nasa.gov/missions/svom.

Planned Retirement of GCN Classic VOEvent Brokers

The result of the November 2024 user survey of those utilizing the GCN VOEvent Brokers to receive VOEvent-format Notices with the VOEvent Transport Protocol is overwhelmingly in favor of retiring the brokers and users migrating to receive VOEvent Notices over Kafka. This service is already available for all GCN Classic Notice types with self-subscription via the Start Streaming Notices Guide. The GCN Classic VOEvent brokers will be retired shortly after the conclusion of the O4 gravitational wave network observing run, currently scheduled for October 7, 2025. We recommend the following actions for users currently utilizing VOEvent via GCN Classic.

• Sign up to receive VOEvent format Notices via Kafka or email
• Let the GCN Team know when you're ready to unsubscribe from receiving them via the GCN Classic brokers. All GCN Classic VOEvent subscribers will be unsubscribed after the end of O4 and the brokers will be taken offline.

GCN at AAS 245, Legacy Circulars Address Retirement

Visit GCN at the NASA Booth at the 245th AAS Meeting

If you are at the 245th AAS meeting in National Harbor, MD on January 12-16, 2025, be sure to stop by the GCN table at the NASA booth in the exhibit hall to:

• play with our Raspberry Pi Kafka demo
• sign up for GCN, if you aren't already subscribed
• collect an all new official GCN patch
• talk with the GCN developers about your feature requests and issues.

Retirement of Legacy Email Submission Address

We retired the legacy email address (gcncirc@capella2.gsfc.nasa.gov) for GCN Circular submission on December 31, 2024. Utilize one of the other Circular submission methods:

• Email circulars@gcn.nasa.gov
• Submit via the web form, which also offers enhanced features with Markdown capability to add tables, links, and formatting.