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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

36198 results found.

  1. GRB 250625A: ABObservatory afterglow detection
  2. GRB 250625A: OHP/T193 optical detection
  3. GRB 250625A: COLIBRÍ optical observations
  4. GRB 250625A: Fermi-LAT detection
  5. GRB 250625A: Swift-XRT refined Analysis
  6. GRB 250625A: JinShan optical observations
  7. GRB250625A: Fermi GBM Observation
  8. Swift GRB 250625A: Global MASTER-Net observations report
  9. GRB 250625A: NOT z-band upper limit
  10. GRB 250625A: SVOM/VT optical confirmation
  11. GRB 250620B: Fermi GBM Observation
  12. GRB 250625A: SAO RAS possible optical afterglow
  13. GRB 250625A: Enhanced Swift-XRT position
  14. Fermi GRB 250625A: Global MASTER-Net observations report
  15. GRB 250625A: Swift detection of a burst
  16. GRB 250625A: Fermi GBM Final Real-time Localization
  17. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  18. GRB 250620A: AstroSat CZTI detection
  19. GRB 241018A: Maidanak optical observations
  20. GRB 250620C: AstroSat CZTI detection
  21. Fermi GRB 250624A: Global MASTER-Net observations report
  22. GRB 250624A: Fermi GBM Final Real-time Localization
  23. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
  24. Fermi GRB 250623A: Global MASTER-Net observations report
  25. GRB 250623A: Fermi GBM Final Real-time Localization
  26. GRB 250521A: VZLUSAT-2 detection
  27. GRB 250617B: Swift-BAT refined analysis
  28. Konus-Wind detection of GRB 250620C
  29. IPN triangulation of GRB 250620C (long/bright)
  30. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  31. GRB 250620C: SVOM/GRM observation
  32. GRB 250620A: SVOM/GRM observation of a short burst
  33. GRB250620A: Fermi GBM Observation
  34. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  35. Fermi GRB 250621A: Global MASTER-Net observations report
  36. GRB 250619B: Fermi GBM Observation
  37. GRB 250621A: Fermi GBM Final Real-time Localization
  38. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  39. GRB250620C: Fermi GBM Observation
  40. GRB 250506A - SVOM/ECLAIRs Refined analysis
  41. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  42. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  43. GRB 250620C: Fermi GBM Final Real-time Localization
  44. GRB 250620B: Fermi GBM Final Real-time Localization
  45. GRB 250620A: Fermi GBM Final Real-time Localization
  46. GRB 250617B: Nickel telescope optical observations
  47. GRB 250619B: Fermi GBM Final Real-time Localization
  48. Fermi Gamma-ray Burst Monitor trigger 772058337/250619860 is not a GRB
  49. GRB 250615A: Kilonova-Catcher optical upper limits
  50. GRB 250619A: Fermi GBM Final Real-time Localization
  51. GRB 250617B: Assy AZT-20 Optical Observations
  52. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  53. Fermi GRB 250617A: Global MASTER-Net observations report
  54. GRB 250615A/EP250615a: FTW optical and NIR observations
  55. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  56. GRB 250617B: Swift/UVOT Detection
  57. GRB 250617B: Kilonova-Catcher optical afterglow detection
  58. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  59. GRB 250617B: COLIBRÍ optical observations
  60. GRB 250617B: NOT NIR observations of the afterglow
  61. GRB 250617B: Swift-XRT refined Analysis
  62. GRB 250617B: SVOM/VT optical observation
  63. GRB 250617B: NUTTelA-TAO early time optical observations
  64. Swift GRB 250617B: Global MASTER-Net observations report
  65. GRB 250617B: GOTO optical upper limit
  66. GRB 250617B: Enhanced Swift-XRT position
  67. GRB 250617B: Fermi GBM Observation
  68. GRB 250615A: Swift-BAT refined analysis
  69. GRB 250617B: Fermi GBM Final Localization
  70. GRB 250617B: Ondrejov D50 optical afterglow detection
  71. GRB 250617B: SAO RAS optical observations
  72. GRB 250617B: Swift detection of a burst with an optical counterpart
  73. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  74. GRB 250617A: Fermi GBM Final Real-time Localization
  75. IPN triangulation of GRB 250612C (short/hard)
  76. Konus-Wind detection of GRB 250615A / EP250615a
  77. GRB 250615A / EP250615a: AstroSat CZTI detection
  78. Fermi Gamma-ray Burst Monitor trigger 771803204/250616907 is not a GRB
  79. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  80. GRB 250615A: COLIBRÍ optical upper limit
  81. GRB 250615A: DDOTI Optical Upper Limit
  82. GRB 250615A: Swift/UVOT Upper Limits
  83. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  84. GRB 250615A: Swift-XRT refined Analysis
  85. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  86. GRB 250615A: Enhanced Swift-XRT position
  87. Fermi Gamma-ray Burst Monitor trigger 771718064/250615922 is not a GRB
  88. GRB 250615A: Prompt enhanced Swift-XRT position
  89. GRB 250615A: Swift detection of a burst
  90. Swift GRB 250615A: Global MASTER-Net observations report
  91. Fermi Gamma-ray Burst Monitor trigger 771704505/250615765 is not a GRB
  92. GRID detection of GRB 250612C
  93. Fermi Gamma-ray Burst Monitor trigger 771596290/250614513 is not a GRB
  94. GRB 250614A: Fermi GBM Final Real-time Localization
  95. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  96. Fermi Gamma-ray Burst Monitor trigger 771547945/250613953 is not a GRB
  97. Fermi Gamma-ray Burst Monitor trigger 771541927/250613883 is not a GRB
  98. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  99. GRB 250612B: Fermi GBM Observation
  100. EP250612a / GRB 250612B: SVOM/VT optical candidate

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