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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"

28257 results found.

  1. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  2. GRB 241018A: Maidanak optical observations
  3. GRB 250620C: AstroSat CZTI detection
  4. Fermi GRB 250624A: Global MASTER-Net observations report
  5. GRB 250521A: VZLUSAT-2 detection
  6. GRB 250617B: Swift-BAT refined analysis
  7. Fermi trigger No 772190032: Global MASTER-Net observations report
  8. IPN triangulation of GRB 250620C (long/bright)
  9. GRB 250620C: SVOM/GRM observation
  10. GRB 250620A: SVOM/GRM observation of a short burst
  11. GRB250620A: Fermi GBM Observation
  12. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  13. GRB 250619B: Fermi GBM Observation
  14. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  15. GRB250620C: Fermi GBM Observation
  16. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  17. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  18. Fermi trigger No 772128434: Global MASTER-Net observations report
  19. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  20. GRB 250617B: Nickel telescope optical observations
  21. GRB 250615A: Kilonova-Catcher optical upper limits
  22. GRB 250617B: Assy AZT-20 Optical Observations
  23. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  24. Fermi GRB 250617A: Global MASTER-Net observations report
  25. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  26. GRB 250617B: Swift/UVOT Detection
  27. GRB 250617B: Kilonova-Catcher optical afterglow detection
  28. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  29. GRB 250617B: COLIBRÍ optical observations
  30. GRB 250617B: NOT NIR observations of the afterglow
  31. GRB 250617B: Swift-XRT refined Analysis
  32. GRB 250617B: NUTTelA-TAO early time optical observations
  33. GRB 250617B: Enhanced Swift-XRT position
  34. GRB 250617B: Fermi GBM Observation
  35. GRB 250615A: Swift-BAT refined analysis
  36. GRB 250617B: SAO RAS optical observations
  37. GRB 250617B: Swift detection of a burst with an optical counterpart
  38. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  39. EP#01709178975: Swift-XRT counterpart detection
  40. EP-WXT trigger 01709178975: GOTO optical upper limit
  41. GRB 250615A / EP250615a: AstroSat CZTI detection
  42. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  43. GRB 250615A: COLIBRÍ optical upper limit
  44. GRB 250615A: DDOTI Optical Upper Limit
  45. GRB 250615A: Swift/UVOT Upper Limits
  46. GRB 250615A: Swift-XRT refined Analysis
  47. sb25061207/SVOM: T120 OHP optical upper limit
  48. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  49. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  50. GRB 250615A: Enhanced Swift-XRT position
  51. GRB 250615A: Swift detection of a burst
  52. Fermi trigger No 771718064: Global MASTER-Net observations report
  53. sb25061207: Mephisto optical upper limits
  54. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  55. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  56. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  57. sb25061218: Swift-XRT observations
  58. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  59. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  60. sb25061207: EP-FXT follow-up observation and afterglow candidate
  61. GRB 250612B: Fermi GBM Observation
  62. EP250612a / GRB 250612B: SVOM/VT optical candidate
  63. GRB 250612C: Fermi GBM Observation
  64. sb25061218: SVOM detection of a X-ray transient
  65. sb25061207: Swift-XRT observations
  66. EP250612a/GRB 250612B: JinShan optical upper limit
  67. sb25061207: SVOM/VT optical counterpart
  68. GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
  69. GRB 250610B: Swift-XRT refined Analysis
  70. EP250610a: Upper limit from Fermi-GBM Observations
  71. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  72. EP250612a: Einstein Probe detection of an X-ray transient
  73. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  74. sb25061207: SVOM detection of a X-ray transient
  75. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  76. Fermi GBM Sub-Threshold Detection of GRB 250610B
  77. GRB 250610B: Swift/UVOT Detection
  78. EP250610A: Swift/UVOT Upper limits
  79. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  80. EP250610a: TNG NIR upper limit
  81. GRB 250610B: REM optical/NIR observations
  82. EP250610a: Liverpool Telescope optical upper limits
  83. GRB 250610B: additional Liverpool Telescope optical observations
  84. GRB 250610B: SVOM/GRM analysis
  85. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  86. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  87. GRB 250610B: Swift-XRT counterpart detection
  88. GRB 250610B: SVOM/VT optical counterpart
  89. GRB 250610B: OHP/T120 optical counterpart candidate
  90. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  91. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  92. GRB 250605A: Swift-BAT refined analysis
  93. EP250610a: SVOM/VT optical upper limit
  94. EP250610a: REM optical/NIR observations
  95. GRB 250609A: Fermi GBM Observation
  96. EP250610a: Swift-XRT counterpart detection
  97. EP250610a: COLIBRÍ optical upper limit
  98. EP250610a: Einstein Probe detection of an X-ray transient
  99. Fermi trigger No 771072240: Global MASTER-Net observations report
  100. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst

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