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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"

32508 results found.

  1. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  2. GRB 250628A: VLT/X-shooter upper limits
  3. GRB 250628A: Swift/UVOT Upper Limits
  4. Fermi GRB 250626A: Global MASTER-Net observations report
  5. Swift GRB 250628A: Global MASTER-Net observations report
  6. GRB 250625A: Swift-BAT refined analysis
  7. GRB 250625A: Leavitt Observatory afterglow detection
  8. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  9. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  10. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  11. GRB 250625A: SVOM/C-GFT upper limit in early phase
  12. GRB 250625A: GECAM-B detection
  13. GRB 250625A: Swift/UVOT Upper Limits
  14. GRB 250625A: ABObservatory afterglow detection
  15. GRB 250625A: OHP/T193 optical detection
  16. GRB 250625A: COLIBRÍ optical observations
  17. GRB 250625A: Fermi-LAT detection
  18. GRB 250625A: JinShan optical observations
  19. GRB250625A: Fermi GBM Observation
  20. Swift GRB 250625A: Global MASTER-Net observations report
  21. GRB 250625A: NOT z-band upper limit
  22. GRB 250625A: SVOM/VT optical confirmation
  23. GRB 250620B: Fermi GBM Observation
  24. GRB 250625A: SAO RAS possible optical afterglow
  25. Fermi GRB 250625A: Global MASTER-Net observations report
  26. GRB 250625A: Swift detection of a burst
  27. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  28. GRB 250620A: AstroSat CZTI detection
  29. GRB 241018A: Maidanak optical observations
  30. GRB 250620C: AstroSat CZTI detection
  31. Fermi GRB 250624A: Global MASTER-Net observations report
  32. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
  33. Fermi GRB 250623A: Global MASTER-Net observations report
  34. GRB 250521A: VZLUSAT-2 detection
  35. GRB 250617B: Swift-BAT refined analysis
  36. Konus-Wind detection of GRB 250620C
  37. IPN triangulation of GRB 250620C (long/bright)
  38. GRB 250620C: SVOM/GRM observation
  39. GRB 250620A: SVOM/GRM observation of a short burst
  40. GRB250620A: Fermi GBM Observation
  41. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  42. Fermi GRB 250621A: Global MASTER-Net observations report
  43. GRB 250619B: Fermi GBM Observation
  44. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  45. GRB 250506A - SVOM/ECLAIRs Refined analysis
  46. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  47. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  48. GRB 250617B: Nickel telescope optical observations
  49. GRB 250615A: Kilonova-Catcher optical upper limits
  50. GRB 250617B: Assy AZT-20 Optical Observations
  51. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  52. Fermi GRB 250617A: Global MASTER-Net observations report
  53. GRB 250615A/EP250615a: FTW optical and NIR observations
  54. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  55. GRB 250617B: Swift/UVOT Detection
  56. GRB 250617B: Kilonova-Catcher optical afterglow detection
  57. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  58. GRB 250617B: COLIBRÍ optical observations
  59. GRB 250617B: NOT NIR observations of the afterglow
  60. GRB 250617B: SVOM/VT optical observation
  61. GRB 250617B: NUTTelA-TAO early time optical observations
  62. Swift GRB 250617B: Global MASTER-Net observations report
  63. GRB 250617B: GOTO optical upper limit
  64. GRB 250617B: Fermi GBM Observation
  65. GRB 250615A: Swift-BAT refined analysis
  66. GRB 250617B: Fermi GBM Final Localization
  67. GRB 250617B: Ondrejov D50 optical afterglow detection
  68. GRB 250617B: SAO RAS optical observations
  69. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  70. IPN triangulation of GRB 250612C (short/hard)
  71. Konus-Wind detection of GRB 250615A / EP250615a
  72. GRB 250615A / EP250615a: AstroSat CZTI detection
  73. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  74. GRB 250615A: COLIBRÍ optical upper limit
  75. GRB 250615A: DDOTI Optical Upper Limit
  76. GRB 250615A: Swift/UVOT Upper Limits
  77. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  78. sb25061207/SVOM: T120 OHP optical upper limit
  79. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  80. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  81. GRID detection of GRB 250612C
  82. sb25061207: Mephisto optical upper limits
  83. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  84. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  85. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  86. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  87. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  88. sb25061207: EP-FXT follow-up observation and afterglow candidate
  89. GRB 250612B: Fermi GBM Observation
  90. EP250612a: SVOM/VT optical candidate
  91. EP250612a: Global MASTER-Net observations report
  92. GRB 250612C: Fermi GBM Observation
  93. sb25061207: Swift-XRT observations
  94. EP250612a/GRB 250612B: JinShan optical upper limit
  95. EP 250612a: AST3-3 Yaoan Optical Observation
  96. GRB 250612C: SVOM/GRM observation an intermedium duration burst
  97. sb25061207: SVOM/VT optical counterpart
  98. EP250610a: Upper limit from Fermi-GBM Observations
  99. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  100. GRB 250610B: Liverpool Telescope continued monitoring

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