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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"

35324 results found.

  1. GRB 250620B: Fermi GBM Observation
  2. GRB 250625A: SAO RAS possible optical afterglow
  3. GRB 250625A: Enhanced Swift-XRT position
  4. Fermi GRB 250625A: Global MASTER-Net observations report
  5. GRB 250625A: Swift detection of a burst
  6. GRB 250625A: Fermi GBM Final Real-time Localization
  7. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  8. GRB 250620A: AstroSat CZTI detection
  9. GRB 241018A: Maidanak optical observations
  10. GRB 250620C: AstroSat CZTI detection
  11. Fermi GRB 250624A: Global MASTER-Net observations report
  12. GRB 250624A: Fermi GBM Final Real-time Localization
  13. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
  14. Fermi GRB 250623A: Global MASTER-Net observations report
  15. GRB 250623A: Fermi GBM Final Real-time Localization
  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 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  21. GRB 250620C: SVOM/GRM observation
  22. GRB 250620A: SVOM/GRM observation of a short burst
  23. GRB250620A: Fermi GBM Observation
  24. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  25. Fermi GRB 250621A: Global MASTER-Net observations report
  26. GRB 250619B: Fermi GBM Observation
  27. GRB 250621A: Fermi GBM Final Real-time Localization
  28. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  29. GRB250620C: Fermi GBM Observation
  30. GRB 250506A - SVOM/ECLAIRs Refined analysis
  31. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  32. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  33. GRB 250620C: Fermi GBM Final Real-time Localization
  34. GRB 250620B: Fermi GBM Final Real-time Localization
  35. GRB 250620A: Fermi GBM Final Real-time Localization
  36. GRB 250617B: Nickel telescope optical observations
  37. GRB 250619B: Fermi GBM Final Real-time Localization
  38. Fermi Gamma-ray Burst Monitor trigger 772058337/250619860 is not a GRB
  39. GRB 250615A: Kilonova-Catcher optical upper limits
  40. GRB 250619A: Fermi GBM Final Real-time Localization
  41. GRB 250617B: Assy AZT-20 Optical Observations
  42. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  43. Fermi GRB 250617A: Global MASTER-Net observations report
  44. GRB 250615A/EP250615a: FTW optical and NIR observations
  45. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  46. GRB 250617B: Swift/UVOT Detection
  47. GRB 250617B: Kilonova-Catcher optical afterglow detection
  48. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  49. GRB 250617B: COLIBRÍ optical observations
  50. GRB 250617B: NOT NIR observations of the afterglow
  51. GRB 250617B: Swift-XRT refined Analysis
  52. GRB 250617B: SVOM/VT optical observation
  53. GRB 250617B: NUTTelA-TAO early time optical observations
  54. Swift GRB 250617B: Global MASTER-Net observations report
  55. GRB 250617B: GOTO optical upper limit
  56. GRB 250617B: Enhanced Swift-XRT position
  57. GRB 250617B: Fermi GBM Observation
  58. GRB 250615A: Swift-BAT refined analysis
  59. GRB 250617B: Fermi GBM Final Localization
  60. GRB 250617B: Ondrejov D50 optical afterglow detection
  61. GRB 250617B: SAO RAS optical observations
  62. GRB 250617B: Swift detection of a burst with an optical counterpart
  63. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  64. GRB 250617A: Fermi GBM Final Real-time Localization
  65. IPN triangulation of GRB 250612C (short/hard)
  66. Konus-Wind detection of GRB 250615A / EP250615a
  67. GRB 250615A / EP250615a: AstroSat CZTI detection
  68. Fermi Gamma-ray Burst Monitor trigger 771803204/250616907 is not a GRB
  69. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  70. GRB 250615A: COLIBRÍ optical upper limit
  71. GRB 250615A: DDOTI Optical Upper Limit
  72. GRB 250615A: Swift/UVOT Upper Limits
  73. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  74. GRB 250615A: Swift-XRT refined Analysis
  75. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  76. GRB 250615A: Enhanced Swift-XRT position
  77. Fermi Gamma-ray Burst Monitor trigger 771718064/250615922 is not a GRB
  78. GRB 250615A: Prompt enhanced Swift-XRT position
  79. GRB 250615A: Swift detection of a burst
  80. Swift GRB 250615A: Global MASTER-Net observations report
  81. Fermi Gamma-ray Burst Monitor trigger 771704505/250615765 is not a GRB
  82. GRID detection of GRB 250612C
  83. Fermi Gamma-ray Burst Monitor trigger 771596290/250614513 is not a GRB
  84. GRB 250614A: Fermi GBM Final Real-time Localization
  85. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  86. Fermi Gamma-ray Burst Monitor trigger 771547945/250613953 is not a GRB
  87. Fermi Gamma-ray Burst Monitor trigger 771541927/250613883 is not a GRB
  88. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  89. GRB 250612B: Fermi GBM Observation
  90. GRB 250612C: Fermi GBM Observation
  91. EP250612a/GRB 250612B: JinShan optical upper limit
  92. GRB 250612C: SVOM/GRM observation an intermedium duration burst
  93. GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
  94. GRB 250610B: Swift-XRT refined Analysis
  95. GRB 250612C: Fermi GBM Final Real-time Localization
  96. EP250610a: Upper limit from Fermi-GBM Observations
  97. GRB 250612B (250612519/771424081): Fermi GBM Final Localization
  98. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  99. GRB 250610B: Liverpool Telescope continued monitoring
  100. GRB 250610B: MISTRAL/T193 and T120 OHP further observations

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