Skip to main content
New! Browse Circulars by Event, Advanced Search, Sample Codes, Schema Release. 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 250617B: NOT NIR observations of the afterglow
  2. GRB 250617B: Swift-XRT refined Analysis
  3. GRB 250617B: SVOM/VT optical observation
  4. GRB 250617B: NUTTelA-TAO early time optical observations
  5. Fermi trigger No 771886893: Global MASTER-Net observations report
  6. Swift GRB 250617B: Global MASTER-Net observations report
  7. GRB 250617B: GOTO optical upper limit
  8. GRB 250617B: Enhanced Swift-XRT position
  9. GRB 250617B: Fermi GBM Observation
  10. GRB 250615A: Swift-BAT refined analysis
  11. The EP-WXT trigger 01709178990 is likely a flaring star
  12. GRB 250617B: Fermi GBM Final Localization
  13. GRB 250617B: Ondrejov D50 optical afterglow detection
  14. GRB 250617B: SAO RAS optical observations
  15. GRB 250617B: Swift detection of a burst with an optical counterpart
  16. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  17. GRB 250617A: Fermi GBM Final Real-time Localization
  18. IPN triangulation of GRB 250612C (short/hard)
  19. EP#01709178975: Swift-XRT counterpart detection
  20. EP-WXT trigger 01709178975: GOTO optical upper limit
  21. The EP-WXT trigger 01709178975 is likely a flaring star
  22. Konus-Wind detection of GRB 250615A / EP250615a
  23. GRB 250615A / EP250615a: AstroSat CZTI detection
  24. Fermi Gamma-ray Burst Monitor trigger 771803204/250616907 is not a GRB
  25. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  26. GRB 250615A: COLIBRÍ optical upper limit
  27. GRB 250615A: DDOTI Optical Upper Limit
  28. GRB 250615A: Swift/UVOT Upper Limits
  29. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  30. GRB 250615A: Swift-XRT refined Analysis
  31. sb25061207/SVOM: T120 OHP optical upper limit
  32. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  33. Fermi trigger No 771752663: Global MASTER-Net observations report
  34. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  35. The EP-WXT trigger 01709178875 is likely a flaring star
  36. GRB 250615A: Enhanced Swift-XRT position
  37. Fermi Gamma-ray Burst Monitor trigger 771718064/250615922 is not a GRB
  38. GRB 250615A: Prompt enhanced Swift-XRT position
  39. GRB 250615A: Swift detection of a burst
  40. Swift GRB 250615A: Global MASTER-Net observations report
  41. Fermi trigger No 771718064: Global MASTER-Net observations report
  42. Fermi Gamma-ray Burst Monitor trigger 771704505/250615765 is not a GRB
  43. GRID detection of GRB 250612C
  44. sb25061207: Mephisto optical upper limits
  45. IceCube alert 141029_8144692 retraction
  46. Fermi Gamma-ray Burst Monitor trigger 771596290/250614513 is not a GRB
  47. GRB 250614A: Fermi GBM Final Real-time Localization
  48. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  49. Fermi Gamma-ray Burst Monitor trigger 771547945/250613953 is not a GRB
  50. Fermi Gamma-ray Burst Monitor trigger 771541927/250613883 is not a GRB
  51. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  52. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  53. Fermi trigger No 771494087: Global MASTER-Net observations report
  54. sb25061218: Swift-XRT observations
  55. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  56. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  57. sb25061207: EP-FXT follow-up observation and afterglow candidate
  58. GRB 250612B: Fermi GBM Observation
  59. EP250612a: SVOM/VT optical candidate
  60. Fermi trigger No 771424081: Global MASTER-Net observations report
  61. EP250612a: Global MASTER-Net observations report
  62. GRB 250612C: Fermi GBM Observation
  63. sb25061218: SVOM detection of a X-ray transient
  64. sb25061207: Swift-XRT observations
  65. EP250612a/GRB 250612B: JinShan optical upper limit
  66. EP 250612a: AST3-3 Yaoan Optical Observation
  67. GRB 250612C: SVOM/GRM observation an intermedium duration burst
  68. sb25061207: SVOM/VT optical counterpart
  69. GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
  70. GRB 250610B: Swift-XRT refined Analysis
  71. GRB 250612C: Fermi GBM Final Real-time Localization
  72. EP250610a: Upper limit from Fermi-GBM Observations
  73. GRB 250612B (250612519/771424081): Fermi GBM Final Localization
  74. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  75. EP250612a: Einstein Probe detection of an X-ray transient
  76. GRB 250610B: Liverpool Telescope continued monitoring
  77. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  78. sb25061207: SVOM detection of a X-ray transient
  79. EP250610a: continuous follow-up observations with EP-FXT
  80. GRB 250610B - SVOM/ECLAIRs refined analysis
  81. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  82. Swift GRB250612.04: Global MASTER-Net observations report
  83. Fermi GBM Sub-Threshold Detection of GRB 250610B
  84. GRB 250610B: Swift/UVOT Detection
  85. EP250610A: Swift/UVOT Upper limits
  86. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  87. EP250610a: TNG NIR upper limit
  88. GRB 250610B: REM optical/NIR observations
  89. EP250610a: Liverpool Telescope optical upper limits
  90. GRB 250610B: SVOM/VT optical shallow decay
  91. GRB 250610B: additional Liverpool Telescope optical observations
  92. GRB 250610B: SVOM/GRM analysis
  93. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  94. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  95. Fermi Gamma-ray Burst Monitor trigger 771286888/250610932 is not a GRB
  96. GRB 250610B: Swift-XRT counterpart detection
  97. GRB 250610B: SVOM/VT optical counterpart
  98. GRB 250610B: LT detection of the optical counterpart
  99. GRB 250610B: OHP/T120 optical counterpart candidate
  100. GRB 250610C: Fermi GBM Final Real-time Localization

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