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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"

32506 results found.

  1. GRB 250628A: VLT/X-shooter upper limits
  2. GRB 250628A: Swift/UVOT Upper Limits
  3. Fermi GRB 250626A: Global MASTER-Net observations report
  4. Swift GRB 250628A: Global MASTER-Net observations report
  5. GRB 250625A: Swift-BAT refined analysis
  6. GRB 250625A: Leavitt Observatory afterglow detection
  7. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  8. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  9. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  10. GRB 250625A: SVOM/C-GFT upper limit in early phase
  11. GRB 250625A: GECAM-B detection
  12. GRB 250625A: Swift/UVOT Upper Limits
  13. GRB 250625A: ABObservatory afterglow detection
  14. GRB 250625A: OHP/T193 optical detection
  15. GRB 250625A: COLIBRÍ optical observations
  16. GRB 250625A: Fermi-LAT detection
  17. GRB 250625A: JinShan optical observations
  18. GRB250625A: Fermi GBM Observation
  19. Swift GRB 250625A: Global MASTER-Net observations report
  20. GRB 250625A: NOT z-band upper limit
  21. GRB 250625A: SVOM/VT optical confirmation
  22. GRB 250620B: Fermi GBM Observation
  23. GRB 250625A: SAO RAS possible optical afterglow
  24. Fermi GRB 250625A: Global MASTER-Net observations report
  25. GRB 250625A: Swift detection of a burst
  26. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  27. GRB 250620A: AstroSat CZTI detection
  28. GRB 241018A: Maidanak optical observations
  29. GRB 250620C: AstroSat CZTI detection
  30. Fermi GRB 250624A: Global MASTER-Net observations report
  31. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
  32. Fermi GRB 250623A: Global MASTER-Net observations report
  33. GRB 250521A: VZLUSAT-2 detection
  34. GRB 250617B: Swift-BAT refined analysis
  35. Konus-Wind detection of GRB 250620C
  36. IPN triangulation of GRB 250620C (long/bright)
  37. GRB 250620C: SVOM/GRM observation
  38. GRB 250620A: SVOM/GRM observation of a short burst
  39. GRB250620A: Fermi GBM Observation
  40. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  41. Fermi GRB 250621A: Global MASTER-Net observations report
  42. GRB 250619B: Fermi GBM Observation
  43. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  44. GRB 250506A - SVOM/ECLAIRs Refined analysis
  45. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  46. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  47. GRB 250617B: Nickel telescope optical observations
  48. GRB 250615A: Kilonova-Catcher optical upper limits
  49. GRB 250617B: Assy AZT-20 Optical Observations
  50. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  51. Fermi GRB 250617A: Global MASTER-Net observations report
  52. GRB 250615A/EP250615a: FTW optical and NIR observations
  53. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  54. GRB 250617B: Swift/UVOT Detection
  55. GRB 250617B: Kilonova-Catcher optical afterglow detection
  56. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  57. GRB 250617B: COLIBRÍ optical observations
  58. GRB 250617B: NOT NIR observations of the afterglow
  59. GRB 250617B: SVOM/VT optical observation
  60. GRB 250617B: NUTTelA-TAO early time optical observations
  61. Swift GRB 250617B: Global MASTER-Net observations report
  62. GRB 250617B: GOTO optical upper limit
  63. GRB 250617B: Fermi GBM Observation
  64. GRB 250615A: Swift-BAT refined analysis
  65. GRB 250617B: Fermi GBM Final Localization
  66. GRB 250617B: Ondrejov D50 optical afterglow detection
  67. GRB 250617B: SAO RAS optical observations
  68. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  69. IPN triangulation of GRB 250612C (short/hard)
  70. Konus-Wind detection of GRB 250615A / EP250615a
  71. GRB 250615A / EP250615a: AstroSat CZTI detection
  72. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  73. GRB 250615A: COLIBRÍ optical upper limit
  74. GRB 250615A: DDOTI Optical Upper Limit
  75. GRB 250615A: Swift/UVOT Upper Limits
  76. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  77. sb25061207/SVOM: T120 OHP optical upper limit
  78. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  79. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  80. GRID detection of GRB 250612C
  81. sb25061207: Mephisto optical upper limits
  82. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  83. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  84. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  85. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  86. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  87. sb25061207: EP-FXT follow-up observation and afterglow candidate
  88. GRB 250612B: Fermi GBM Observation
  89. EP250612a: SVOM/VT optical candidate
  90. EP250612a: Global MASTER-Net observations report
  91. GRB 250612C: Fermi GBM Observation
  92. sb25061207: Swift-XRT observations
  93. EP250612a/GRB 250612B: JinShan optical upper limit
  94. EP 250612a: AST3-3 Yaoan Optical Observation
  95. GRB 250612C: SVOM/GRM observation an intermedium duration burst
  96. sb25061207: SVOM/VT optical counterpart
  97. EP250610a: Upper limit from Fermi-GBM Observations
  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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