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Frequently Asked Questions

Common Questions

How do I connect to the CHIME/FRB VOEvent Service?

The service requires a (free) subscription that can be requested here.

We just received a VOEvent, is it a FRB?

Not every alert will represent a true FRB! Because alerts are published in real-time they are only verified by a human after you reveive the VOEvent. To check the status of a particular alert, join or start a discussion here.

We used the service for follow-up observations, what should we do next?

We ask that you cite any CHIME/FRB VOEvents that were used to trigger your follow-up observations by their VOEvent IVORN and in addition cite the usage of the Service with the following statement:

This research has made use of the CHIME/FRB VOEvent Service.

How do we get help regarding issues about the service

Please consult our GitHub community discussion page here. You can search for existing issues first to see if your problem, or similar, has already been solved or is being actively investigated; otherwise, consider starting a discussion there.

How can I contact the CHIME/FRB team for quick questions?

Please check to see if your question is answered here. If not, consider starting a new discussion, and a CHIME/FRB team member will help out in the forum in a timely manner.

VOEvent Service Questions

Connection Issues

If you are having problems connecting to the Service, you can try these solutions that have been ranked in order of severity/complexity.

Request Subscription

Check your records whether you have an active subscription. This would have required filling the subscription form which provides a receipt to the email address that requested it.

Activation Time

Provide atleast 3 working days since submitting the subscription request, thereby allowing enough time for CHIME/FRB to activate your subscription.

Valid IP Address

Check that the IP address of the machine where you VOEvent broker is running is publicly accessible, not blocked by a firewall, not behind a local router and exactly matches the one you gave in the subscription form.

Further Problems

Please summarize the problem in a detailed GitHub issue here and be sure to include the following details in the issue.

  • Subscriber details: email address, name, and academic association you gave when filling the subscription form
  • Operating System (e.g. Linux)
  • VOEvent broker software and version (e.g. Comet v 3.1.0)
  • Screenshots or code captures of any messages that your broker reports while trying to subscribe. To obtain detailed diagnostic information, run your VOEvent broker in non-demonized mode and high verbosity - for example, see Comet documentation here.

Technical Questions

The known_source_name Parameter

You may see an integer reported as the name of the source in a subsequent VOEvent, rather than a TNS name. This number is an internal event registration number for CHIME/FRB, indicating that the source is not yet public.

Proper credit for CHIME/FRB VOEvent Service

Whenever providing credir in publications/ATels, please be sure to use the VOEvent IVORN when referencing individual VOEvents that refer to FRBs, and include the following citation statement:

This research has made use of the CHIME/FRB VOEvent Service.

Known telescopes/instruments using CHIME/FRB VOEvents

The following is a recent list of all observatories, telescopes, and instruments currently using CHIME/FRB VOEvents.

  • Swift-GUANO
  • Hat Creek Radio Observatory
Does CHIME/FRB issue retractions for spurious events?

Real-time VOEvents are verified by humans only after they have been VOEvent has been published. Following human verification, an event may be found to be a false positive signal, for example due to RFI contamination. While the real-time FRB detection pipeline performs multiple levels of RFI excision, it is not a perfect filter.

Under the current regime, once per day around 22:00 Pacific Standard Time we will publish retraction VOEvents in bulk for all false positives classified in the previous 24 hour period.

How precise and accurate is the localization region in the VOEvent?

The real-time localization is reported as an on-sky circle in celestial coordinates. The precision and accurcy of this circular region is sensitive to whether the FRB was detected in one beam or multiple beams.


Multi-beam FRB detections typically come with the least precise real-time localization. The error radius can be as large as 1 to 2 degrees, and larger in rare instances. Typically the worst localizations are for events that later turn out to be RFI that was detected in many beams.

Single-beam FRB detections are typically circular regions with a radius equal to half the detection beam width at 600 MHz, which is about 0.5 degrees. However, it can be much better in some instances, as low as 10 arcminutes.


The accuracy of real-time localizations has been evaluated and described in CHIME/FRB Collaboration et al., 2019, using the method of pulsar analogues.

Which FRB parameters are most important?

Every subscriber has constructed a potentially unique follow-up campaign. For instance, one may be interested in low dispersion measure (DM) FRBs, while another is interested in follow-up of specific known repeating FRBs. For that reason, the FRB parameters of import vary from one campaign to the next. For example, the dm and snr parameters in every VOEvent can be used with thresholds to trigger on CHIME-detected FRBs that have low DM and high-SNR, to study FRBs that are potentially in the local Universe. In a different scenario, a threshold on timestamp_utc is important for campaigns looking to achieve very low latency follow-up.