Skip to main content
Retirement of GCN Classic VOEvent Brokers. 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. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  2. GRB 260502A: GECAM-B observation of a short burst
  3. IPN triangulation of a bright burst from SGR 1E1841-045
  4. GRB 260502A: Fermi GBM Final Localization
  5. The EP-WXT trigger 01709261576 is likely a flaring star
  6. GRB 260429B / EP260429a: EP-FXT follow-up observation
  7. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  8. GRB 260429B / EP260429a: AstroSat CZTI detection
  9. GRB EP260502a: BOOTES-7: early optical upper limit
  10. EP260502a: Las Cumbres upper limit
  11. EP260502a: Einstein Probe detection of an X-ray transient
  12. GRB 260429A: SVOM/GRM observation of a short burst
  13. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  14. EP260429a: Global MASTER-Net observations report
  15. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  16. GRB 260424B: AstroSat CZTI detection
  17. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  18. EP260429a: LCO optical upper limits
  19. EP260430a: LCO optical upper limits
  20. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  21. GRB 260429A: Fermi GBM Detection
  22. Fermi GRB 260429A: Global MASTER-Net observations report
  23. EP260430a: Global MASTER-Net observations report
  24. EP260430a: Einstein Probe detection of an X-ray transient
  25. EP260429a: EP-WXT detection of a fast X-ray transient
  26. GRB 260429A: Fermi GBM Final Real-time Localization
  27. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  28. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  29. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  30. GRB 260428A: AstroSat CZTI detection
  31. Fermi GRB 260428A: Global MASTER-Net observations report
  32. EP260416a: Mondy and Terskol optical upper limits
  33. GRB 260424B: Glowbug gamma-ray detection of a short burst
  34. GRB 260424B: COLIBRÍ optical upper limit
  35. Konus-Wind detection of GRB 260424B
  36. GRB 260428A: Fermi GBM Final Real-time Localization
  37. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  38. GRB 260424C: Fermi GBM Final Localization
  39. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  40. IPN triangulation of GRB 260424B (short)
  41. GRB 260424B: SVOM/GRM detection of a short burst
  42. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  43. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  44. IceCube Alert 260425A: Global MASTER-Net observations report
  45. Fermi trigger No 798737427: Global MASTER-Net observations report
  46. GRB 260401A: cubesat Avion detection
  47. GRB 260424A: AstroSat CZTI detection of a long burst
  48. EP260321a: Upper limits from ATCA radio observations
  49. GRB 260421B: Kilonova-Catcher optical afterglow detection
  50. GRB 260421B: Insight-HXMT/HE detection
  51. The EP-WXT trigger 01709258652: Mondy optical observations
  52. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  53. EP260416a: Mondy optical observations
  54. GRB 260421B: SVOM/ECLAIRs refined analysis
  55. GRB 260421B: 3.6m DOT optical observation
  56. EP260416a: ZTSh R band observations
  57. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  58. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  59. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  60. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  61. GRB 260419A: AstroSat CZTI detection
  62. GRB 260421B: SVOM/GRM observation
  63. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  64. GRB 260421B: EP-FXT follow-up observation
  65. The EP-WXT trigger 01709260362 is likely a flaring star
  66. GOTO26djh/AT2026jpw: ATCA radio detection
  67. GRB 260421B: J-band upper limit with WINTER
  68. GRB 260421B: LCO optical counterpart detection
  69. GRB 260421B: Fermi GBM Observation
  70. Fermi Gamma-ray Burst Monitor trigger 798482368/260421694 is not a GRB
  71. GRB 260421A: AstroSat CZTI detection
  72. GOTO26djh/AT2026jpw: radio detection at 15GHz
  73. GRB 260412A: SVOM/ECLAIRs refined analysis
  74. GRB 260421B: SVOM/VT optical observations
  75. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  76. GRB 260310A: Late-time Chandra X-ray Detection
  77. GRB 260418A: Insight-HXMT/HE detection
  78. EP260416a: 1.3m DFOT optical observation
  79. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  80. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  81. Fermi GRB 260421C: Global MASTER-Net observations report
  82. GRB 260421C: Fermi GBM Final Real-time Localization
  83. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  84. Fermi GRB 260421B: Global MASTER-Net observations report
  85. GRB 260421B: BOOTES-7 early optical afterglow detection
  86. GRB 260421B: LCO optical afterglow confirmation
  87. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  88. GRB 260421B: TRT optical counterpart detection
  89. GRB 260421B: SVOM detection of a long burst
  90. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  91. GRB 260421B: Fermi GBM Final Real-time Localization
  92. Fermi GRB 260421A: Global MASTER-Net observations report
  93. GRB 260421A: Fermi GBM Final Real-time Localization
  94. EP260321a: VLA radio follow-up
  95. GRB 260412A: LCOGT Optical Upper Limits
  96. The EP-WXT trigger 01709260314 is likely a flaring star
  97. EP260416a: Optical follow-up observations with Kinder
  98. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  99. EP-WXT trigger 01709260303: KAIT optical observations
  100. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring

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