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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"

35946 results found.

  1. GRB 250702F: MASTER optical afterglow observation
  2. Fermi GRB 250702F: Global MASTER-Net observations report
  3. Fermi GRB 250702C: Global MASTER-Net observations report
  4. GRB 250702F: GOTO optical counterpart detection
  5. GRB 250702F: Ondrejov D50 optical afterglow detection
  6. GRB 250702F: Swift detection of a burst with an optical counterpart
  7. Swift GRB 250702F: Global MASTER-Net observations report
  8. GRB 250702F: Fermi GBM Final Real-time Localization
  9. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  10. GRB 250702E: Fermi GBM Final Real-time Localization
  11. Konus-Wind detection of GRB 250627A
  12. IPN triangulation of GRB 250627A (short)
  13. GRB 250702A: Fermi GBM Detection
  14. GRB 250702D: Fermi GBM Final Localization Correction
  15. GRB 250702C: Fermi GBM Final Real-time Localization
  16. GRB 250702B: Fermi GBM Final Real-time Localization
  17. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  18. GRB 250702A: Fermi GBM Final Real-time Localization
  19. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  20. GRB 250628B: Swift-XRT observations
  21. Fermi Gamma-ray Burst Monitor trigger 772981768/250630548 is not a GRB
  22. GRB 250628B: SVOM/VT optical upper limit
  23. GRB 250628B: EP-FXT counterpart detection
  24. GRB 250627A: Insight-HXMT detection
  25. GRB 250627A: SVOM/GRM detection of a short burst
  26. GRB 250628A: REM optical/NIR upper limits
  27. GRB 250628C: Fermi GBM Final Real-time Localization
  28. GRB 250628B: SVOM detection of a long burst
  29. Fermi Gamma-ray Burst Monitor trigger 772811638/250628579 is not a GRB
  30. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  31. GRB 250628A: VLT/X-shooter upper limits
  32. GRB 250628A: Swift/UVOT Upper Limits
  33. GRB 250628A: Swift-XRT refined Analysis
  34. Fermi GRB 250626A: Global MASTER-Net observations report
  35. Swift GRB 250628A: Global MASTER-Net observations report
  36. GRB 250628A: Enhanced Swift-XRT position
  37. GRB 250628A: Swift detection of a burst
  38. GRB 250625A: Swift-BAT refined analysis
  39. GRB 250625A: Leavitt Observatory afterglow detection
  40. Fermi Gamma-ray Burst Monitor trigger 772732642/250627665 is not a GRB
  41. Fermi Gamma-ray Burst Monitor trigger 772720540/250627525 is not a GRB
  42. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  43. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  44. GRB 250626A: Fermi GBM Final Real-time Localization
  45. Fermi Gamma-ray Burst Monitor trigger 772647532/250626680 is not a GRB
  46. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  47. GRB 250625A: SVOM/C-GFT upper limit in early phase
  48. GRB 250625A: GECAM-B detection
  49. GRB 250625A: Swift/UVOT Upper Limits
  50. GRB 250625A: ABObservatory afterglow detection
  51. GRB 250625A: OHP/T193 optical detection
  52. GRB 250625A: COLIBRÍ optical observations
  53. GRB 250625A: Fermi-LAT detection
  54. GRB 250625A: Swift-XRT refined Analysis
  55. GRB 250625A: JinShan optical observations
  56. GRB250625A: Fermi GBM Observation
  57. Swift GRB 250625A: Global MASTER-Net observations report
  58. GRB 250625A: NOT z-band upper limit
  59. GRB 250625A: SVOM/VT optical confirmation
  60. GRB 250620B: Fermi GBM Observation
  61. GRB 250625A: SAO RAS possible optical afterglow
  62. GRB 250625A: Enhanced Swift-XRT position
  63. Fermi GRB 250625A: Global MASTER-Net observations report
  64. GRB 250625A: Swift detection of a burst
  65. GRB 250625A: Fermi GBM Final Real-time Localization
  66. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  67. GRB 250620A: AstroSat CZTI detection
  68. GRB 241018A: Maidanak optical observations
  69. GRB 250620C: AstroSat CZTI detection
  70. Fermi GRB 250624A: Global MASTER-Net observations report
  71. GRB 250624A: Fermi GBM Final Real-time Localization
  72. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
  73. Fermi GRB 250623A: Global MASTER-Net observations report
  74. GRB 250623A: Fermi GBM Final Real-time Localization
  75. GRB 250521A: VZLUSAT-2 detection
  76. GRB 250617B: Swift-BAT refined analysis
  77. Konus-Wind detection of GRB 250620C
  78. IPN triangulation of GRB 250620C (long/bright)
  79. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  80. GRB 250620C: SVOM/GRM observation
  81. GRB 250620A: SVOM/GRM observation of a short burst
  82. GRB250620A: Fermi GBM Observation
  83. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  84. Fermi GRB 250621A: Global MASTER-Net observations report
  85. GRB 250619B: Fermi GBM Observation
  86. GRB 250621A: Fermi GBM Final Real-time Localization
  87. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  88. GRB250620C: Fermi GBM Observation
  89. GRB 250506A - SVOM/ECLAIRs Refined analysis
  90. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  91. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  92. GRB 250620C: Fermi GBM Final Real-time Localization
  93. GRB 250620B: Fermi GBM Final Real-time Localization
  94. GRB 250620A: Fermi GBM Final Real-time Localization
  95. GRB 250617B: Nickel telescope optical observations
  96. GRB 250619B: Fermi GBM Final Real-time Localization
  97. Fermi Gamma-ray Burst Monitor trigger 772058337/250619860 is not a GRB
  98. GRB 250615A: Kilonova-Catcher optical upper limits
  99. GRB 250619A: Fermi GBM Final Real-time Localization
  100. GRB 250617B: Assy AZT-20 Optical Observations

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