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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"

38328 results found.

  1. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  2. GRB 250702F: Swift-XRT refined Analysis
  3. GRB 250702F: Fermi GBM Observation
  4. GRB 250702F: Leavitt Observatory optical observations
  5. GRB 250702F: AKO Optical Afterglow Detection
  6. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  7. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  8. GRB 250702A: GECAM-B detection
  9. GRB 250702F: Skynet Optical Observations
  10. GRB 250424A: VIRT Optical Upper Limit
  11. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  12. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  13. GRB 250702F: TRT Optical Observation
  14. GRB 250703A: DDOTI Optical Upper Limit
  15. GRB 250702F: REM optical afterglow detection
  16. EP250702a: Global MASTER-Net observations report
  17. GRB 250702F: DDOTI Optical Observation
  18. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  19. GRB 250703A: Fermi GBM Final Real-time Localization
  20. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  21. GRB 250702F: COLIBRÍ Observations of the Afterglow
  22. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  23. Fermi GRB 250702E: Global MASTER-Net observations report
  24. Fermi GRB 250702B: Global MASTER-Net observations report
  25. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  26. GRB 250702F: Enhanced Swift-XRT position
  27. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  28. GRB 250702F: NOT observations of the optical afterglow
  29. GRB 250702F: MASTER optical afterglow observation
  30. Fermi GRB 250702F: Global MASTER-Net observations report
  31. Fermi GRB 250702C: Global MASTER-Net observations report
  32. GRB 250702F: GOTO optical counterpart detection
  33. GRB 250702F: Ondrejov D50 optical afterglow detection
  34. GRB 250702F: Swift detection of a burst with an optical counterpart
  35. Swift GRB 250702F: Global MASTER-Net observations report
  36. GRB 250702F: Fermi GBM Final Real-time Localization
  37. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  38. GRB 250702E: Fermi GBM Final Real-time Localization
  39. Konus-Wind detection of GRB 250627A
  40. IPN triangulation of GRB 250627A (short)
  41. GRB 250702A: Fermi GBM Detection
  42. GRB 250702D: Fermi GBM Final Localization Correction
  43. GRB 250702C: Fermi GBM Final Real-time Localization
  44. GRB 250702B: Fermi GBM Final Real-time Localization
  45. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  46. GRB 250702A: Fermi GBM Final Real-time Localization
  47. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  48. GRB 250628B: Swift-XRT observations
  49. Fermi Gamma-ray Burst Monitor trigger 772981768/250630548 is not a GRB
  50. GRB 250628B: SVOM/VT optical upper limit
  51. GRB 250628B: EP-FXT counterpart detection
  52. GRB 250627A: Insight-HXMT detection
  53. GRB 250627A: SVOM/GRM detection of a short burst
  54. GRB 250628A: REM optical/NIR upper limits
  55. GRB 250628C: Fermi GBM Final Real-time Localization
  56. GRB 250628B: SVOM detection of a long burst
  57. Fermi Gamma-ray Burst Monitor trigger 772811638/250628579 is not a GRB
  58. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  59. GRB 250628A: VLT/X-shooter upper limits
  60. GRB 250628A: Swift/UVOT Upper Limits
  61. GRB 250628A: Swift-XRT refined Analysis
  62. Fermi GRB 250626A: Global MASTER-Net observations report
  63. Swift GRB 250628A: Global MASTER-Net observations report
  64. GRB 250628A: Enhanced Swift-XRT position
  65. GRB 250628A: Swift detection of a burst
  66. GRB 250625A: Swift-BAT refined analysis
  67. GRB 250625A: Leavitt Observatory afterglow detection
  68. Fermi Gamma-ray Burst Monitor trigger 772732642/250627665 is not a GRB
  69. Fermi Gamma-ray Burst Monitor trigger 772720540/250627525 is not a GRB
  70. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  71. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  72. GRB 250626A: Fermi GBM Final Real-time Localization
  73. Fermi Gamma-ray Burst Monitor trigger 772647532/250626680 is not a GRB
  74. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  75. GRB 250625A: SVOM/C-GFT upper limit in early phase
  76. GRB 250625A: GECAM-B detection
  77. GRB 250625A: Swift/UVOT Upper Limits
  78. GRB 250625A: ABObservatory afterglow detection
  79. GRB 250625A: OHP/T193 optical detection
  80. GRB 250625A: COLIBRÍ optical observations
  81. GRB 250625A: Fermi-LAT detection
  82. GRB 250625A: Swift-XRT refined Analysis
  83. GRB 250625A: JinShan optical observations
  84. GRB250625A: Fermi GBM Observation
  85. Swift GRB 250625A: Global MASTER-Net observations report
  86. GRB 250625A: NOT z-band upper limit
  87. GRB 250625A: SVOM/VT optical confirmation
  88. GRB 250620B: Fermi GBM Observation
  89. GRB 250625A: SAO RAS possible optical afterglow
  90. GRB 250625A: Enhanced Swift-XRT position
  91. Fermi GRB 250625A: Global MASTER-Net observations report
  92. GRB 250625A: Swift detection of a burst
  93. GRB 250625A: Fermi GBM Final Real-time Localization
  94. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  95. GRB 250620A: AstroSat CZTI detection
  96. GRB 241018A: Maidanak optical observations
  97. GRB 250620C: AstroSat CZTI detection
  98. Fermi GRB 250624A: Global MASTER-Net observations report
  99. GRB 250624A: Fermi GBM Final Real-time Localization
  100. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis

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