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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"

11535 results found.

  1. GRB 250702D: Fermi GBM Final Localization Correction
  2. GRB 250702C: Fermi GBM Final Real-time Localization
  3. GRB 250702B: Fermi GBM Final Real-time Localization
  4. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  5. GRB 250702A: Fermi GBM Final Real-time Localization
  6. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  7. Fermi Gamma-ray Burst Monitor trigger 772981768/250630548 is not a GRB
  8. GRB 250628C: Fermi GBM Final Real-time Localization
  9. Fermi Gamma-ray Burst Monitor trigger 772811638/250628579 is not a GRB
  10. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  11. Fermi GRB 250626A: Global MASTER-Net observations report
  12. GRB 250625A: Leavitt Observatory afterglow detection
  13. Fermi Gamma-ray Burst Monitor trigger 772732642/250627665 is not a GRB
  14. Fermi Gamma-ray Burst Monitor trigger 772720540/250627525 is not a GRB
  15. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  16. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  17. GRB 250626A: Fermi GBM Final Real-time Localization
  18. Fermi Gamma-ray Burst Monitor trigger 772647532/250626680 is not a GRB
  19. GRB 250625A: SVOM/C-GFT upper limit in early phase
  20. GRB 250625A: GECAM-B detection
  21. GRB 250625A: ABObservatory afterglow detection
  22. GRB 250625A: OHP/T193 optical detection
  23. GRB 250625A: COLIBRÍ optical observations
  24. GRB 250625A: Fermi-LAT detection
  25. GRB 250625A: JinShan optical observations
  26. GRB250625A: Fermi GBM Observation
  27. GRB 250625A: NOT z-band upper limit
  28. GRB 250625A: SVOM/VT optical confirmation
  29. GRB 250620B: Fermi GBM Observation
  30. GRB 250625A: SAO RAS possible optical afterglow
  31. Fermi GRB 250625A: Global MASTER-Net observations report
  32. GRB 250625A: Swift detection of a burst
  33. GRB 250625A: Fermi GBM Final Real-time Localization
  34. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  35. GRB 250620A: AstroSat CZTI detection
  36. GRB 250620C: AstroSat CZTI detection
  37. Fermi GRB 250624A: Global MASTER-Net observations report
  38. GRB 250624A: Fermi GBM Final Real-time Localization
  39. Fermi GRB 250623A: Global MASTER-Net observations report
  40. GRB 250623A: Fermi GBM Final Real-time Localization
  41. GRB 250521A: VZLUSAT-2 detection
  42. Fermi trigger No 772190032: Global MASTER-Net observations report
  43. Konus-Wind detection of GRB 250620C
  44. IPN triangulation of GRB 250620C (long/bright)
  45. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  46. GRB 250620C: SVOM/GRM observation
  47. GRB 250620A: SVOM/GRM observation of a short burst
  48. GRB250620A: Fermi GBM Observation
  49. Fermi GRB 250621A: Global MASTER-Net observations report
  50. GRB 250619B: Fermi GBM Observation
  51. GRB 250621A: Fermi GBM Final Real-time Localization
  52. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  53. GRB250620C: Fermi GBM Observation
  54. GRB 250506A - SVOM/ECLAIRs Refined analysis
  55. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  56. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  57. GRB 250620C: Fermi GBM Final Real-time Localization
  58. Fermi trigger No 772128434: Global MASTER-Net observations report
  59. GRB 250620B: Fermi GBM Final Real-time Localization
  60. GRB 250620A: Fermi GBM Final Real-time Localization
  61. GRB 250617B: Nickel telescope optical observations
  62. GRB 250619B: Fermi GBM Final Real-time Localization
  63. Fermi trigger No 772058337: Global MASTER-Net observations report
  64. Fermi Gamma-ray Burst Monitor trigger 772058337/250619860 is not a GRB
  65. GRB 250619A: Fermi GBM Final Real-time Localization
  66. GRB 250617B: Assy AZT-20 Optical Observations
  67. Fermi GRB 250617A: Global MASTER-Net observations report
  68. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  69. GRB 250617B: COLIBRÍ optical observations
  70. GRB 250617B: NOT NIR observations of the afterglow
  71. GRB 250617B: SVOM/VT optical observation
  72. Fermi trigger No 771886893: Global MASTER-Net observations report
  73. GRB 250617B: GOTO optical upper limit
  74. GRB 250617B: Fermi GBM Observation
  75. GRB 250617B: Fermi GBM Final Localization
  76. GRB 250617A: Fermi GBM Final Real-time Localization
  77. IPN triangulation of GRB 250612C (short/hard)
  78. Fermi Gamma-ray Burst Monitor trigger 771803204/250616907 is not a GRB
  79. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  80. Fermi trigger No 771752663: Global MASTER-Net observations report
  81. Fermi Gamma-ray Burst Monitor trigger 771718064/250615922 is not a GRB
  82. Fermi trigger No 771718064: Global MASTER-Net observations report
  83. Fermi Gamma-ray Burst Monitor trigger 771704505/250615765 is not a GRB
  84. GRID detection of GRB 250612C
  85. Fermi Gamma-ray Burst Monitor trigger 771596290/250614513 is not a GRB
  86. GRB 250614A: Fermi GBM Final Real-time Localization
  87. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  88. Fermi Gamma-ray Burst Monitor trigger 771547945/250613953 is not a GRB
  89. Fermi Gamma-ray Burst Monitor trigger 771541927/250613883 is not a GRB
  90. Fermi trigger No 771494087: Global MASTER-Net observations report
  91. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  92. GRB 250612B: Fermi GBM Observation
  93. Fermi trigger No 771424081: Global MASTER-Net observations report
  94. GRB 250612C: Fermi GBM Observation
  95. EP250612a/GRB 250612B: JinShan optical upper limit
  96. EP 250612a: AST3-3 Yaoan Optical Observation
  97. GRB 250612C: SVOM/GRM observation an intermedium duration burst
  98. GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
  99. GRB 250612C: Fermi GBM Final Real-time Localization
  100. EP250610a: Upper limit from Fermi-GBM Observations

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