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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"

20491 results found.

  1. GRB 250702F: Ondrejov D50 optical afterglow detection
  2. Swift GRB 250702F: Global MASTER-Net observations report
  3. GRB 250628B: Swift-XRT observations
  4. GRB 250628B: SVOM/VT optical upper limit
  5. GRB 250628A: REM optical/NIR upper limits
  6. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  7. GRB 250628A: Swift/UVOT Upper Limits
  8. Fermi GRB 250626A: Global MASTER-Net observations report
  9. Swift GRB 250628A: Global MASTER-Net observations report
  10. GRB 250625A: Leavitt Observatory afterglow detection
  11. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  12. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  13. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  14. GRB 250625A: SVOM/C-GFT upper limit in early phase
  15. GRB 250625A: Swift/UVOT Upper Limits
  16. GRB 250625A: ABObservatory afterglow detection
  17. GRB 250625A: OHP/T193 optical detection
  18. GRB 250625A: COLIBRÍ optical observations
  19. GRB 250625A: JinShan optical observations
  20. Swift GRB 250625A: Global MASTER-Net observations report
  21. GRB 250625A: SAO RAS possible optical afterglow
  22. Fermi GRB 250625A: Global MASTER-Net observations report
  23. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  24. GRB 241018A: Maidanak optical observations
  25. Fermi GRB 250624A: Global MASTER-Net observations report
  26. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
  27. Fermi GRB 250623A: Global MASTER-Net observations report
  28. Fermi trigger No 772190032: Global MASTER-Net observations report
  29. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  30. Fermi GRB 250621A: Global MASTER-Net observations report
  31. GRB 250506A - SVOM/ECLAIRs Refined analysis
  32. Fermi trigger No 772128434: Global MASTER-Net observations report
  33. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  34. GRB 250617B: Nickel telescope optical observations
  35. Fermi trigger No 772058337: Global MASTER-Net observations report
  36. GRB 250615A: Kilonova-Catcher optical upper limits
  37. GRB 250617B: Assy AZT-20 Optical Observations
  38. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  39. Fermi GRB 250617A: Global MASTER-Net observations report
  40. GRB 250615A/EP250615a: FTW optical and NIR observations
  41. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  42. GRB 250617B: Swift/UVOT Detection
  43. GRB 250617B: Kilonova-Catcher optical afterglow detection
  44. GRB 250617B: COLIBRÍ optical observations
  45. GRB 250617B: NOT NIR observations of the afterglow
  46. GRB 250617B: NUTTelA-TAO early time optical observations
  47. Fermi trigger No 771886893: Global MASTER-Net observations report
  48. Swift GRB 250617B: Global MASTER-Net observations report
  49. GRB 250617B: GOTO optical upper limit
  50. GRB 250617B: SAO RAS optical observations
  51. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  52. EP#01709178975: Swift-XRT counterpart detection
  53. EP-WXT trigger 01709178975: GOTO optical upper limit
  54. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  55. GRB 250615A: DDOTI Optical Upper Limit
  56. GRB 250615A: Swift/UVOT Upper Limits
  57. Fermi trigger No 771752663: Global MASTER-Net observations report
  58. Swift GRB 250615A: Global MASTER-Net observations report
  59. Fermi trigger No 771718064: Global MASTER-Net observations report
  60. sb25061207: Mephisto optical upper limits
  61. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  62. Fermi trigger No 771494087: Global MASTER-Net observations report
  63. sb25061218: Swift-XRT observations
  64. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  65. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  66. Fermi trigger No 771424081: Global MASTER-Net observations report
  67. EP250612a: Global MASTER-Net observations report
  68. sb25061207: Swift-XRT observations
  69. EP250612a/GRB 250612B: JinShan optical upper limit
  70. EP250610a: Upper limit from Fermi-GBM Observations
  71. GRB 250610B: Liverpool Telescope continued monitoring
  72. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  73. EP250610a: continuous follow-up observations with EP-FXT
  74. GRB 250610B - SVOM/ECLAIRs refined analysis
  75. Swift GRB250612.04: Global MASTER-Net observations report
  76. GRB 250610B: Swift/UVOT Detection
  77. EP250610A: Swift/UVOT Upper limits
  78. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  79. GRB 250610B: REM optical/NIR observations
  80. GRB 250610B: SVOM/VT optical shallow decay
  81. GRB 250610B: additional Liverpool Telescope optical observations
  82. GRB 250610B: Swift-XRT counterpart detection
  83. GRB 250610B: LT detection of the optical counterpart
  84. GRB 250610B: GOTO optical upper limit
  85. EP250610a: Global MASTER-Net observations report
  86. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  87. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  88. EP250610a: REM optical/NIR observations
  89. EP250610a: Swift-XRT counterpart detection
  90. EP250610a: COLIBRÍ optical upper limit
  91. Fermi trigger No 771072240: Global MASTER-Net observations report
  92. GRB 250605A: Swift/UVOT Upper Limits
  93. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  94. GRB 250527C: CrAO Optical Upper Limit
  95. EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  96. EP-WXT trigger 01709178069: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  97. GRB 250605A: SVOM/VT optical upper limit
  98. EP/WXT 01709177873: GOTO observations confirm stellar variability
  99. Fermi GRB 250606A: Global MASTER-Net observations report
  100. Fermi trigger No 770867684: Global MASTER-Net observations report

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