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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"

32689 results found.

  1. GRB250625A: Fermi GBM Observation
  2. Swift GRB 250625A: Global MASTER-Net observations report
  3. GRB 250625A: NOT z-band upper limit
  4. GRB 250625A: SVOM/VT optical confirmation
  5. GRB 250620B: Fermi GBM Observation
  6. GRB 250625A: SAO RAS possible optical afterglow
  7. Fermi GRB 250625A: Global MASTER-Net observations report
  8. GRB 250625A: Swift detection of a burst
  9. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  10. GRB 250620A: AstroSat CZTI detection
  11. GRB 241018A: Maidanak optical observations
  12. GRB 250620C: AstroSat CZTI detection
  13. Fermi GRB 250624A: Global MASTER-Net observations report
  14. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
  15. Fermi GRB 250623A: Global MASTER-Net observations report
  16. GRB 250521A: VZLUSAT-2 detection
  17. GRB 250617B: Swift-BAT refined analysis
  18. Konus-Wind detection of GRB 250620C
  19. IPN triangulation of GRB 250620C (long/bright)
  20. GRB 250620C: SVOM/GRM observation
  21. GRB 250620A: SVOM/GRM observation of a short burst
  22. GRB250620A: Fermi GBM Observation
  23. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  24. Fermi GRB 250621A: Global MASTER-Net observations report
  25. GRB 250619B: Fermi GBM Observation
  26. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  27. GRB 250506A - SVOM/ECLAIRs Refined analysis
  28. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  29. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  30. GRB 250617B: Nickel telescope optical observations
  31. GRB 250615A: Kilonova-Catcher optical upper limits
  32. GRB 250617B: Assy AZT-20 Optical Observations
  33. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  34. Fermi GRB 250617A: Global MASTER-Net observations report
  35. GRB 250615A/EP250615a: FTW optical and NIR observations
  36. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  37. GRB 250617B: Swift/UVOT Detection
  38. GRB 250617B: Kilonova-Catcher optical afterglow detection
  39. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  40. GRB 250617B: COLIBRÍ optical observations
  41. GRB 250617B: NOT NIR observations of the afterglow
  42. GRB 250617B: SVOM/VT optical observation
  43. GRB 250617B: NUTTelA-TAO early time optical observations
  44. Swift GRB 250617B: Global MASTER-Net observations report
  45. GRB 250617B: GOTO optical upper limit
  46. GRB 250617B: Fermi GBM Observation
  47. GRB 250615A: Swift-BAT refined analysis
  48. GRB 250617B: Fermi GBM Final Localization
  49. GRB 250617B: Ondrejov D50 optical afterglow detection
  50. GRB 250617B: SAO RAS optical observations
  51. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  52. IPN triangulation of GRB 250612C (short/hard)
  53. Konus-Wind detection of GRB 250615A / EP250615a
  54. GRB 250615A / EP250615a: AstroSat CZTI detection
  55. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  56. GRB 250615A: COLIBRÍ optical upper limit
  57. GRB 250615A: DDOTI Optical Upper Limit
  58. GRB 250615A: Swift/UVOT Upper Limits
  59. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  60. sb25061207/SVOM: T120 OHP optical upper limit
  61. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  62. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  63. GRID detection of GRB 250612C
  64. sb25061207: Mephisto optical upper limits
  65. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  66. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  67. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  68. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  69. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  70. sb25061207: EP-FXT follow-up observation and afterglow candidate
  71. GRB 250612B: Fermi GBM Observation
  72. EP250612a / GRB 250612B: SVOM/VT optical candidate
  73. EP250612a: Global MASTER-Net observations report
  74. GRB 250612C: Fermi GBM Observation
  75. sb25061207: Swift-XRT observations
  76. EP250612a/GRB 250612B: JinShan optical upper limit
  77. EP 250612a: AST3-3 Yaoan Optical Observation
  78. GRB 250612C: SVOM/GRM observation an intermedium duration burst
  79. sb25061207: SVOM/VT optical counterpart
  80. EP250610a: Upper limit from Fermi-GBM Observations
  81. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  82. GRB 250610B: Liverpool Telescope continued monitoring
  83. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  84. EP250610a: continuous follow-up observations with EP-FXT
  85. GRB 250610B - SVOM/ECLAIRs refined analysis
  86. Fermi GBM Sub-Threshold Detection of GRB 250610B
  87. GRB 250610B: Swift/UVOT Detection
  88. EP250610A: Swift/UVOT Upper limits
  89. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  90. EP250610a: TNG NIR upper limit
  91. GRB 250610B: REM optical/NIR observations
  92. EP250610a: Liverpool Telescope optical upper limits
  93. GRB 250610B: SVOM/VT optical shallow decay
  94. GRB 250610B: additional Liverpool Telescope optical observations
  95. GRB 250610B: SVOM/GRM analysis
  96. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  97. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  98. GRB 250610B: Swift-XRT counterpart detection
  99. GRB 250610B: SVOM/VT optical counterpart
  100. GRB 250610B: LT detection of the optical counterpart

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