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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"

36210 results found.

  1. GRB 250702A: Fermi GBM Final Real-time Localization
  2. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  3. GRB 250628B: Swift-XRT observations
  4. Fermi Gamma-ray Burst Monitor trigger 772981768/250630548 is not a GRB
  5. GRB 250628B: SVOM/VT optical upper limit
  6. GRB 250628B: EP-FXT counterpart detection
  7. GRB 250627A: Insight-HXMT detection
  8. GRB 250627A: SVOM/GRM detection of a short burst
  9. GRB 250628A: REM optical/NIR upper limits
  10. GRB 250628C: Fermi GBM Final Real-time Localization
  11. GRB 250628B: SVOM detection of a long burst
  12. Fermi Gamma-ray Burst Monitor trigger 772811638/250628579 is not a GRB
  13. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  14. GRB 250628A: VLT/X-shooter upper limits
  15. GRB 250628A: Swift/UVOT Upper Limits
  16. GRB 250628A: Swift-XRT refined Analysis
  17. Fermi GRB 250626A: Global MASTER-Net observations report
  18. Swift GRB 250628A: Global MASTER-Net observations report
  19. GRB 250628A: Enhanced Swift-XRT position
  20. GRB 250628A: Swift detection of a burst
  21. GRB 250625A: Swift-BAT refined analysis
  22. GRB 250625A: Leavitt Observatory afterglow detection
  23. Fermi Gamma-ray Burst Monitor trigger 772732642/250627665 is not a GRB
  24. Fermi Gamma-ray Burst Monitor trigger 772720540/250627525 is not a GRB
  25. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  26. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  27. GRB 250626A: Fermi GBM Final Real-time Localization
  28. Fermi Gamma-ray Burst Monitor trigger 772647532/250626680 is not a GRB
  29. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  30. GRB 250625A: SVOM/C-GFT upper limit in early phase
  31. GRB 250625A: GECAM-B detection
  32. GRB 250625A: Swift/UVOT Upper Limits
  33. GRB 250625A: ABObservatory afterglow detection
  34. GRB 250625A: OHP/T193 optical detection
  35. GRB 250625A: COLIBRÍ optical observations
  36. GRB 250625A: Fermi-LAT detection
  37. GRB 250625A: Swift-XRT refined Analysis
  38. GRB 250625A: JinShan optical observations
  39. GRB250625A: Fermi GBM Observation
  40. Swift GRB 250625A: Global MASTER-Net observations report
  41. GRB 250625A: NOT z-band upper limit
  42. GRB 250625A: SVOM/VT optical confirmation
  43. GRB 250620B: Fermi GBM Observation
  44. GRB 250625A: SAO RAS possible optical afterglow
  45. GRB 250625A: Enhanced Swift-XRT position
  46. Fermi GRB 250625A: Global MASTER-Net observations report
  47. GRB 250625A: Swift detection of a burst
  48. GRB 250625A: Fermi GBM Final Real-time Localization
  49. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  50. GRB 250620A: AstroSat CZTI detection
  51. GRB 241018A: Maidanak optical observations
  52. GRB 250620C: AstroSat CZTI detection
  53. Fermi GRB 250624A: Global MASTER-Net observations report
  54. GRB 250624A: Fermi GBM Final Real-time Localization
  55. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
  56. Fermi GRB 250623A: Global MASTER-Net observations report
  57. GRB 250623A: Fermi GBM Final Real-time Localization
  58. GRB 250521A: VZLUSAT-2 detection
  59. GRB 250617B: Swift-BAT refined analysis
  60. Konus-Wind detection of GRB 250620C
  61. IPN triangulation of GRB 250620C (long/bright)
  62. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  63. GRB 250620C: SVOM/GRM observation
  64. GRB 250620A: SVOM/GRM observation of a short burst
  65. GRB250620A: Fermi GBM Observation
  66. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  67. Fermi GRB 250621A: Global MASTER-Net observations report
  68. GRB 250619B: Fermi GBM Observation
  69. GRB 250621A: Fermi GBM Final Real-time Localization
  70. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  71. GRB250620C: Fermi GBM Observation
  72. GRB 250506A - SVOM/ECLAIRs Refined analysis
  73. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  74. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  75. GRB 250620C: Fermi GBM Final Real-time Localization
  76. GRB 250620B: Fermi GBM Final Real-time Localization
  77. GRB 250620A: Fermi GBM Final Real-time Localization
  78. GRB 250617B: Nickel telescope optical observations
  79. GRB 250619B: Fermi GBM Final Real-time Localization
  80. Fermi Gamma-ray Burst Monitor trigger 772058337/250619860 is not a GRB
  81. GRB 250615A: Kilonova-Catcher optical upper limits
  82. GRB 250619A: Fermi GBM Final Real-time Localization
  83. GRB 250617B: Assy AZT-20 Optical Observations
  84. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  85. Fermi GRB 250617A: Global MASTER-Net observations report
  86. GRB 250615A/EP250615a: FTW optical and NIR observations
  87. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  88. GRB 250617B: Swift/UVOT Detection
  89. GRB 250617B: Kilonova-Catcher optical afterglow detection
  90. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  91. GRB 250617B: COLIBRÍ optical observations
  92. GRB 250617B: NOT NIR observations of the afterglow
  93. GRB 250617B: Swift-XRT refined Analysis
  94. GRB 250617B: SVOM/VT optical observation
  95. GRB 250617B: NUTTelA-TAO early time optical observations
  96. Swift GRB 250617B: Global MASTER-Net observations report
  97. GRB 250617B: GOTO optical upper limit
  98. GRB 250617B: Enhanced Swift-XRT position
  99. GRB 250617B: Fermi GBM Observation
  100. GRB 250615A: Swift-BAT refined analysis

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