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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"
  1. GRB 250617B: Swift-BAT refined analysis
  2. Fermi trigger No 772190032: Global MASTER-Net observations report
  3. Konus-Wind detection of GRB 250620C
  4. IPN triangulation of GRB 250620С (long/bright)
  5. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  6. GRB 250620C: SVOM/GRM observation
  7. GRB 250620A: SVOM/GRM observation of a short burst
  8. GRB250620A: Fermi GBM Observation
  9. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  10. Fermi GRB 250621A: Global MASTER-Net observations report
  11. GRB 250619B: Fermi GBM Observation
  12. GRB 250621A: Fermi GBM Final Real-time Localization
  13. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  14. GRB250620C: Fermi GBM Observation
  15. GRB 250506A - SVOM/ECLAIRs Refined analysis
  16. The EP-WXT trigger 01709179071 is likely a flaring star
  17. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  18. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  19. GRB 250620C: Fermi GBM Final Real-time Localization
  20. Fermi trigger No 772128434: Global MASTER-Net observations report
  21. GRB 250620B: Fermi GBM Final Real-time Localization
  22. GRB 250620A: Fermi GBM Final Real-time Localization
  23. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  24. GRB 250617B: Nickel telescope optical observations
  25. GRB 250619B: Fermi GBM Final Real-time Localization
  26. Fermi trigger No 772058337: Global MASTER-Net observations report
  27. Fermi Gamma-ray Burst Monitor trigger 772058337/250619860 is not a GRB
  28. GRB 250615A: Kilonova-Catcher optical upper limits
  29. GRB 250619A: Fermi GBM Final Real-time Localization
  30. GRB 250617B: Assy AZT-20 Optical Observations
  31. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  32. Fermi GRB 250617A: Global MASTER-Net observations report
  33. GRB 250615A/EP250615a: FTW optical and NIR observations
  34. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  35. GRB 250617B: Swift/UVOT Detection
  36. GRB 250617B: Kilonova-Catcher optical afterglow detection
  37. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  38. GRB 250617B: COLIBRÍ optical observations
  39. GRB 250617B: NOT NIR observations of the afterglow
  40. GRB 250617B: Swift-XRT refined Analysis
  41. GRB 250617B: SVOM/VT optical observation
  42. GRB 250617B: NUTTelA-TAO early time optical observations
  43. Fermi trigger No 771886893: Global MASTER-Net observations report
  44. Swift GRB 250617B: Global MASTER-Net observations report
  45. GRB 250617B: GOTO optical upper limit
  46. GRB 250617B: Enhanced Swift-XRT position
  47. GRB 250617B: Fermi GBM Observation
  48. GRB 250615A: Swift-BAT refined analysis
  49. The EP-WXT trigger 01709178990 is likely a flaring star
  50. GRB 250617B: Fermi GBM Final Localization
  51. GRB 250617B: Ondrejov D50 optical afterglow detection
  52. GRB 250617B: SAO RAS optical observations
  53. GRB 250617B: Swift detection of a burst with an optical counterpart
  54. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  55. GRB 250617A: Fermi GBM Final Real-time Localization
  56. IPN triangulation of GRB 250612C (short/hard)
  57. EP#01709178975: Swift-XRT counterpart detection
  58. EP-WXT trigger 01709178975: GOTO optical upper limit
  59. The EP-WXT trigger 01709178975 is likely a flaring star
  60. Konus-Wind detection of GRB 250615A / EP250615a
  61. GRB 250615A / EP250615a: AstroSat CZTI detection
  62. Fermi Gamma-ray Burst Monitor trigger 771803204/250616907 is not a GRB
  63. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  64. GRB 250615A: COLIBRÍ optical upper limit
  65. GRB 250615A: DDOTI Optical Upper Limit
  66. GRB 250615A: Swift/UVOT Upper Limits
  67. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  68. GRB 250615A: Swift-XRT refined Analysis
  69. sb25061207/SVOM: T120 OHP optical upper limit
  70. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  71. Fermi trigger No 771752663: Global MASTER-Net observations report
  72. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  73. The EP-WXT trigger 01709178875 is likely a flaring star
  74. GRB 250615A: Enhanced Swift-XRT position
  75. Fermi Gamma-ray Burst Monitor trigger 771718064/250615922 is not a GRB
  76. GRB 250615A: Prompt enhanced Swift-XRT position
  77. GRB 250615A: Swift detection of a burst
  78. Swift GRB250615.93: Global MASTER-Net observations report
  79. Fermi trigger No 771718064: Global MASTER-Net observations report
  80. Fermi Gamma-ray Burst Monitor trigger 771704505/250615765 is not a GRB
  81. GRID detection of GRB 250612C
  82. sb25061207: Mephisto optical upper limits
  83. IceCube alert 141029_8144692 retraction
  84. Fermi Gamma-ray Burst Monitor trigger 771596290/250614513 is not a GRB
  85. GRB 250614A: Fermi GBM Final Real-time Localization
  86. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  87. Fermi Gamma-ray Burst Monitor trigger 771547945/250613953 is not a GRB
  88. Fermi Gamma-ray Burst Monitor trigger 771541927/250613883 is not a GRB
  89. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  90. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  91. Fermi trigger No 771494087: Global MASTER-Net observations report
  92. sb25061218: Swift-XRT observations
  93. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  94. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  95. sb25061207: EP-FXT follow-up observation and afterglow candidate
  96. GRB 250612B: Fermi GBM Observation
  97. EP250612a: SVOM/VT optical candidate
  98. Fermi trigger No 771424081: Global MASTER-Net observations report
  99. EP250612a: Global MASTER-Net observations report
  100. GRB 250612C: Fermi GBM Observation

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