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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"

35152 results found.

  1. GRB 250617B: Nickel telescope optical observations
  2. GRB 250619B: Fermi GBM Final Real-time Localization
  3. Fermi Gamma-ray Burst Monitor trigger 772058337/250619860 is not a GRB
  4. GRB 250615A: Kilonova-Catcher optical upper limits
  5. GRB 250619A: Fermi GBM Final Real-time Localization
  6. GRB 250617B: Assy AZT-20 Optical Observations
  7. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  8. Fermi GRB 250617A: Global MASTER-Net observations report
  9. GRB 250615A/EP250615a: FTW optical and NIR observations
  10. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  11. GRB 250617B: Swift/UVOT Detection
  12. GRB 250617B: Kilonova-Catcher optical afterglow detection
  13. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  14. GRB 250617B: COLIBRÍ optical observations
  15. GRB 250617B: NOT NIR observations of the afterglow
  16. GRB 250617B: Swift-XRT refined Analysis
  17. GRB 250617B: SVOM/VT optical observation
  18. GRB 250617B: NUTTelA-TAO early time optical observations
  19. Swift GRB 250617B: Global MASTER-Net observations report
  20. GRB 250617B: GOTO optical upper limit
  21. GRB 250617B: Enhanced Swift-XRT position
  22. GRB 250617B: Fermi GBM Observation
  23. GRB 250615A: Swift-BAT refined analysis
  24. GRB 250617B: Fermi GBM Final Localization
  25. GRB 250617B: Ondrejov D50 optical afterglow detection
  26. GRB 250617B: SAO RAS optical observations
  27. GRB 250617B: Swift detection of a burst with an optical counterpart
  28. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  29. GRB 250617A: Fermi GBM Final Real-time Localization
  30. IPN triangulation of GRB 250612C (short/hard)
  31. Konus-Wind detection of GRB 250615A / EP250615a
  32. GRB 250615A / EP250615a: AstroSat CZTI detection
  33. Fermi Gamma-ray Burst Monitor trigger 771803204/250616907 is not a GRB
  34. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  35. GRB 250615A: COLIBRÍ optical upper limit
  36. GRB 250615A: DDOTI Optical Upper Limit
  37. GRB 250615A: Swift/UVOT Upper Limits
  38. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  39. GRB 250615A: Swift-XRT refined Analysis
  40. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  41. GRB 250615A: Enhanced Swift-XRT position
  42. Fermi Gamma-ray Burst Monitor trigger 771718064/250615922 is not a GRB
  43. GRB 250615A: Prompt enhanced Swift-XRT position
  44. GRB 250615A: Swift detection of a burst
  45. Swift GRB 250615A: Global MASTER-Net observations report
  46. Fermi Gamma-ray Burst Monitor trigger 771704505/250615765 is not a GRB
  47. GRID detection of GRB 250612C
  48. Fermi Gamma-ray Burst Monitor trigger 771596290/250614513 is not a GRB
  49. GRB 250614A: Fermi GBM Final Real-time Localization
  50. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  51. Fermi Gamma-ray Burst Monitor trigger 771547945/250613953 is not a GRB
  52. Fermi Gamma-ray Burst Monitor trigger 771541927/250613883 is not a GRB
  53. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  54. GRB 250612B: Fermi GBM Observation
  55. GRB 250612C: Fermi GBM Observation
  56. EP250612a/GRB 250612B: JinShan optical upper limit
  57. GRB 250612C: SVOM/GRM observation an intermedium duration burst
  58. GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
  59. GRB 250610B: Swift-XRT refined Analysis
  60. GRB 250612C: Fermi GBM Final Real-time Localization
  61. EP250610a: Upper limit from Fermi-GBM Observations
  62. GRB 250612B (250612519/771424081): Fermi GBM Final Localization
  63. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  64. GRB 250610B: Liverpool Telescope continued monitoring
  65. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  66. GRB 250610B - SVOM/ECLAIRs refined analysis
  67. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  68. Fermi GBM Sub-Threshold Detection of GRB 250610B
  69. GRB 250610B: Swift/UVOT Detection
  70. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  71. GRB 250610B: REM optical/NIR observations
  72. GRB 250610B: SVOM/VT optical shallow decay
  73. GRB 250610B: additional Liverpool Telescope optical observations
  74. GRB 250610B: SVOM/GRM analysis
  75. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  76. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  77. Fermi Gamma-ray Burst Monitor trigger 771286888/250610932 is not a GRB
  78. GRB 250610B: Swift-XRT counterpart detection
  79. GRB 250610B: SVOM/VT optical counterpart
  80. GRB 250610B: LT detection of the optical counterpart
  81. GRB 250610B: OHP/T120 optical counterpart candidate
  82. GRB 250610C: Fermi GBM Final Real-time Localization
  83. GRB 250610B: GOTO optical upper limit
  84. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  85. GRB 250610B: SVOM detection of a long burst
  86. Fermi Gamma-ray Burst Monitor trigger 771256110/250610575 is not a GRB
  87. GRB 250610A: Fermi GBM Final Real-time Localization
  88. GRB 250605A: Swift-BAT refined analysis
  89. GRB 250609A: Fermi GBM Observation
  90. GRBAlpha reentry on June 9, 2025
  91. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  92. GRB 250605A: Swift/UVOT Upper Limits
  93. GRB 250608A: SVOM/GRM detection of a possible magnetar X-ray burst
  94. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  95. GRB 250527C: CrAO Optical Upper Limit
  96. GRB 250609A: Fermi GBM Final Real-time Localization
  97. GRB 250607A: SVOM/GRM observation of a long burst
  98. GRB 250607A: Fermi GBM Final Localization
  99. GRB 250605A: SVOM/VT optical upper limit
  100. GRB 250605A: Swift-XRT refined Analysis

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