Skip to main content
New! BOOM Notices and Schema v7.0.0. See news and announcements

GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
  1. GRB 250919A: BALROG localization (Fermi Trigger 779934537 / GRB 250919020)
  2. EP250919a: Global MASTER-Net observations report
  3. EP250919a: Einstein Probe detection of an X-ray transient
  4. Correction for GCN 41877: EP-WXT ID is 01709243841
  5. The EP-WXT trigger 01709243841: Las Cumbres discovery of the optical counterpart
  6. GRB 250916A: Fermi GBM Observation
  7. Fermi GRB 250919A: Global MASTER-Net observations report
  8. GRB 250919A: Fermi GBM Final Real-time Localization
  9. GRB 250916A: KAIT optical observations
  10. GRB 250917B: VLT/HAWK-I near-infrared observations
  11. GRB 250916A: NuSTAR detection of the prompt emission
  12. GRB 250916A: further SAO RAS optical observations
  13. GRB 250912A: SVOM/ECLAIRs refined analysis
  14. GRB 250917B: Swift-BAT refined analysis
  15. LIGO/Virgo/KAGRA S250918aw: 1 counterpart neutrino candidate event from an IceCube neutrino search
  16. GRB 250918A: BALROG localization (Fermi Trigger 779891543 / GRB 250918522)
  17. GRB 250918A: Fermi GBM Final Real-time Localization
  18. GRB 250917B: Swift/UVOT Upper Limits
  19. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  20. GRB 250916A: Swift-XRT observations
  21. EP250916a: EP-FXT follow-up observation
  22. GRB 250916A: MAO/AZT-22 optical observations
  23. GRB 250916A: SAO RAS optical observations
  24. GRB 250916A : GIT optical observations
  25. LIGO/Virgo/KAGRA S250917aq: Three counterpart neutrino candidates from IceCube neutrino searches
  26. LIGO/Virgo/KAGRA S250917aq: Updated Sky localization
  27. GRB 250916A: Glowbug gamma-ray detection
  28. GRB250917B: WFST optical observations
  29. GRB 250916A: Swift ToO observations
  30. GRB 250917B: Fermi GBM Observation
  31. GRB 250917B: Swift-XRT observations
  32. LIGO/Virgo/KAGRA S250917aq: Identification of a GW compact binary merger candidate
  33. Fermi GRB 250917B: Global MASTER-Net observations report
  34. GRB 250917B: Swift detection of a short burst
  35. GRB 250916A: GOTO optical counterpart candidate
  36. GRB 250917B: Fermi GBM Final Real-time Localization
  37. GRB 250917A: Fermi GBM Final Real-time Localization
  38. The EP-WXT trigger 01709241037 is likely a flaring star
  39. GRB 250916A: AstroSat CZTI detection of a bright long burst
  40. GRB 250910A: SVOM/ECLAIRs refined analysis
  41. EP250916a: Einstein Probe detection of an X-ray transient
  42. Fermi GRB 250916A: Global MASTER-Net observations report
  43. GRB 250916A: Fermi GBM Final Real-time Localization
  44. EP250827b: VLA Observations
  45. LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
  46. SVOM/sb25091517: Confirmation of a stellar flare by SVOM/VT
  47. SVOM/sb25091517: FRAM-ORM stellar flare - transient observation
  48. SVOM/sb25091517: SVOM detection of an X-ray transient
  49. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  50. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  51. GRB 250912A: Swift-XRT observations
  52. GRB250912A: VLT/HAWK-I follow-up observations
  53. GRB 250912A: VLT observations
  54. GRB 250912A: Fermi GBM Observation
  55. GRB 250911A: Insight-HXMT detection
  56. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  57. GRB 250912A:SVOM/VT optical upper limit
  58. GRB 250912A: LCO optical upper limit
  59. The EP-WXT trigger 01709240768 is likely a flaring star
  60. Fermi GRB 250912A: Global MASTER-Net observations report
  61. EP250911a: Global MASTER-Net observations report
  62. GRB 250912A: SVOM detection of a burst
  63. GRB 250912A: Fermi GBM Final Real-time Localization
  64. IceCube-Cascade 250911A: Upper limits from a search for additional neutrino events in IceCube
  65. LIGO/Virgo/KAGRA S250912s: 2 counterpart neutrino candidate events from an IceCube neutrino search
  66. EP250908c: tentative VLT/FORS2 redshift z = 2.87
  67. EP250911a: Upper limit from Fermi-GBM Observations
  68. LIGO/Virgo/KAGRA S250912f: Updated Sky localization
  69. GRB 250911A: GECAM-B detection
  70. GRB 250911A: Swift-BAT refined analysis
  71. EP250911a: GTC/OSIRIS+ spectroscopic redshift z = 3.84
  72. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  73. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  74. GRB 250910B: SVOM/GRM observation
  75. EP250911a: SVOM/VT optical observation
  76. GRB 250911A: MASTER optical counterpart observations
  77. EP250911a: SAO RAS optical observations
  78. GRB 250911A: Swift-XRT refined Analysis
  79. GRB 250910C: Fermi GBM Final Localization Correction
  80. EP250911a: Swift-XRT observations
  81. EP250911a: Optical detection with Kinder observations
  82. GRB 250911A: Swift/UVOT Detection
  83. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  84. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  85. GRB 250909B: Insight-HXMT detection
  86. GRB 250909B: SVOM/GRM observation
  87. LIGO/Virgo/KAGRA S250911ac: Updated Sky localization and Source Classification
  88. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  89. EP250911a: COLIBRÍ optical observations
  90. LIGO/Virgo/KAGRA S250908y: Updated Sky localization
  91. Fermi GRB 250910B: Global MASTER-Net observations report
  92. EP250911a: LCO optical counterpart discovery
  93. EP250910a: Global MASTER-Net observations report
  94. EP250911a: Einstein Probe detection of an X-ray transient
  95. GRB 250404A / EP250404a: spectroscopic redshift at z = 1.88 (correction to GCN 40084)
  96. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  97. GRB 250903A: SVOM/ECLAIRs refined analysis
  98. GRB 250911A: Enhanced Swift-XRT position
  99. GRB 250911A: Swift-XRT observations
  100. GRB 250911A: COLIBRÍ optical counterpart candidate

Advanced

Download all Circulars as a .tar.gz archive:
Questions or comments?
Contact GCN directly.
Have you found a bug in GCN?
Open an issue.
Want to contribute code to GCN?
Get involved on GitHub.

gcn.nasa.gov

A service of the Astrophysics Science Division at NASA Goddard Space Flight Center

Looking for U.S. government information and services? Visit USA.gov