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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"

36204 results found.

  1. GRB 250702A: GECAM-B detection
  2. GRB 250702F: Skynet Optical Observations
  3. GRB 250424A: VIRT Optical Upper Limit
  4. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  5. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  6. GRB 250702F: TRT Optical Observation
  7. GRB 250703A: DDOTI Optical Upper Limit
  8. GRB 250702F: REM optical afterglow detection
  9. GRB 250702F: DDOTI Optical Observation
  10. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  11. GRB 250703A: Fermi GBM Final Real-time Localization
  12. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  13. GRB 250702F: COLIBRÍ Observations of the Afterglow
  14. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  15. Fermi GRB 250702E: Global MASTER-Net observations report
  16. Fermi GRB 250702B: Global MASTER-Net observations report
  17. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  18. GRB 250702F: Enhanced Swift-XRT position
  19. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  20. GRB 250702F: NOT observations of the optical afterglow
  21. GRB 250702F: MASTER optical afterglow observation
  22. Fermi GRB 250702F: Global MASTER-Net observations report
  23. Fermi GRB 250702C: Global MASTER-Net observations report
  24. GRB 250702F: GOTO optical counterpart detection
  25. GRB 250702F: Ondrejov D50 optical afterglow detection
  26. GRB 250702F: Swift detection of a burst with an optical counterpart
  27. Swift GRB 250702F: Global MASTER-Net observations report
  28. GRB 250702F: Fermi GBM Final Real-time Localization
  29. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  30. GRB 250702E: Fermi GBM Final Real-time Localization
  31. Konus-Wind detection of GRB 250627A
  32. IPN triangulation of GRB 250627A (short)
  33. GRB 250702A: Fermi GBM Detection
  34. GRB 250702D: Fermi GBM Final Localization Correction
  35. GRB 250702C: Fermi GBM Final Real-time Localization
  36. GRB 250702B: Fermi GBM Final Real-time Localization
  37. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  38. GRB 250702A: Fermi GBM Final Real-time Localization
  39. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  40. GRB 250628B: Swift-XRT observations
  41. Fermi Gamma-ray Burst Monitor trigger 772981768/250630548 is not a GRB
  42. GRB 250628B: SVOM/VT optical upper limit
  43. GRB 250628B: EP-FXT counterpart detection
  44. GRB 250627A: Insight-HXMT detection
  45. GRB 250627A: SVOM/GRM detection of a short burst
  46. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate (duplicate submission)
  47. GRB 250628A: REM optical/NIR upper limits
  48. GRB 250628C: Fermi GBM Final Real-time Localization
  49. GRB 250628B: SVOM detection of a long burst
  50. Fermi Gamma-ray Burst Monitor trigger 772811638/250628579 is not a GRB
  51. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  52. GRB 250628A: VLT/X-shooter upper limits
  53. GRB 250628A: Swift/UVOT Upper Limits
  54. GRB 250628A: Swift-XRT refined Analysis
  55. Fermi GRB 250626A: Global MASTER-Net observations report
  56. Swift GRB 250628A: Global MASTER-Net observations report
  57. GRB 250628A: Enhanced Swift-XRT position
  58. GRB 250628A: Swift detection of a burst
  59. GRB 250625A: Swift-BAT refined analysis
  60. GRB 250625A: Leavitt Observatory afterglow detection
  61. Fermi Gamma-ray Burst Monitor trigger 772732642/250627665 is not a GRB
  62. Fermi Gamma-ray Burst Monitor trigger 772720540/250627525 is not a GRB
  63. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  64. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  65. GRB 250626A: Fermi GBM Final Real-time Localization
  66. Fermi Gamma-ray Burst Monitor trigger 772647532/250626680 is not a GRB
  67. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  68. GRB 250625A: SVOM/C-GFT upper limit in early phase
  69. GRB 250625A: GECAM-B detection
  70. GRB 250625A: Swift/UVOT Upper Limits
  71. GRB 250625A: ABObservatory afterglow detection
  72. GRB 250625A: OHP/T193 optical detection
  73. GRB 250625A: COLIBRÍ optical observations
  74. GRB 250625A: Fermi-LAT detection
  75. GRB 250625A: Swift-XRT refined Analysis
  76. GRB 250625A: JinShan optical observations
  77. GRB250625A: Fermi GBM Observation
  78. Swift GRB 250625A: Global MASTER-Net observations report
  79. GRB 250625A: NOT z-band upper limit
  80. GRB 250625A: SVOM/VT optical confirmation
  81. GRB 250620B: Fermi GBM Observation
  82. GRB 250625A: SAO RAS possible optical afterglow
  83. GRB 250625A: Enhanced Swift-XRT position
  84. Fermi GRB 250625A: Global MASTER-Net observations report
  85. GRB 250625A: Swift detection of a burst
  86. GRB 250625A: Fermi GBM Final Real-time Localization
  87. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  88. GRB 250620A: AstroSat CZTI detection
  89. GRB 241018A: Maidanak optical observations
  90. GRB 250620C: AstroSat CZTI detection
  91. Fermi GRB 250624A: Global MASTER-Net observations report
  92. GRB 250624A: Fermi GBM Final Real-time Localization
  93. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
  94. Fermi GRB 250623A: Global MASTER-Net observations report
  95. GRB 250623A: Fermi GBM Final Real-time Localization
  96. GRB 250521A: VZLUSAT-2 detection
  97. GRB 250617B: Swift-BAT refined analysis
  98. Konus-Wind detection of GRB 250620C
  99. IPN triangulation of GRB 250620C (long/bright)
  100. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst

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