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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"

36216 results found.

  1. GRB 250704A: SVOM detection of a burst
  2. GRB 250702F: Swift/UVOT Detection
  3. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  4. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  5. Fermi GRB 250703A: Global MASTER-Net observations report
  6. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  7. GRB 250702F: Swift-XRT refined Analysis
  8. GRB 250702F: Fermi GBM Observation
  9. GRB 250702F: Leavitt Observatory optical observations
  10. GRB 250702F: AKO Optical Afterglow Detection
  11. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  12. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  13. GRB 250702A: GECAM-B detection
  14. GRB 250702F: Skynet Optical Observations
  15. GRB 250424A: VIRT Optical Upper Limit
  16. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  17. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  18. GRB 250702F: TRT Optical Observation
  19. GRB 250703A: DDOTI Optical Upper Limit
  20. GRB 250702F: REM optical afterglow detection
  21. GRB 250702F: DDOTI Optical Observation
  22. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  23. GRB 250703A: Fermi GBM Final Real-time Localization
  24. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  25. GRB 250702F: COLIBRÍ Observations of the Afterglow
  26. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  27. Fermi GRB 250702E: Global MASTER-Net observations report
  28. Fermi GRB 250702B: Global MASTER-Net observations report
  29. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  30. GRB 250702F: Enhanced Swift-XRT position
  31. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  32. GRB 250702F: NOT observations of the optical afterglow
  33. GRB 250702F: MASTER optical afterglow observation
  34. Fermi GRB 250702F: Global MASTER-Net observations report
  35. Fermi GRB 250702C: Global MASTER-Net observations report
  36. GRB 250702F: GOTO optical counterpart detection
  37. GRB 250702F: Ondrejov D50 optical afterglow detection
  38. GRB 250702F: Swift detection of a burst with an optical counterpart
  39. Swift GRB 250702F: Global MASTER-Net observations report
  40. GRB 250702F: Fermi GBM Final Real-time Localization
  41. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  42. GRB 250702E: Fermi GBM Final Real-time Localization
  43. Konus-Wind detection of GRB 250627A
  44. IPN triangulation of GRB 250627A (short)
  45. GRB 250702A: Fermi GBM Detection
  46. GRB 250702D: Fermi GBM Final Localization Correction
  47. GRB 250702C: Fermi GBM Final Real-time Localization
  48. GRB 250702B: Fermi GBM Final Real-time Localization
  49. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  50. GRB 250702A: Fermi GBM Final Real-time Localization
  51. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  52. GRB 250628B: Swift-XRT observations
  53. Fermi Gamma-ray Burst Monitor trigger 772981768/250630548 is not a GRB
  54. GRB 250628B: SVOM/VT optical upper limit
  55. GRB 250628B: EP-FXT counterpart detection
  56. GRB 250627A: Insight-HXMT detection
  57. GRB 250627A: SVOM/GRM detection of a short burst
  58. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate (duplicate submission)
  59. GRB 250628A: REM optical/NIR upper limits
  60. GRB 250628C: Fermi GBM Final Real-time Localization
  61. GRB 250628B: SVOM detection of a long burst
  62. Fermi Gamma-ray Burst Monitor trigger 772811638/250628579 is not a GRB
  63. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  64. GRB 250628A: VLT/X-shooter upper limits
  65. GRB 250628A: Swift/UVOT Upper Limits
  66. GRB 250628A: Swift-XRT refined Analysis
  67. Fermi GRB 250626A: Global MASTER-Net observations report
  68. Swift GRB 250628A: Global MASTER-Net observations report
  69. GRB 250628A: Enhanced Swift-XRT position
  70. GRB 250628A: Swift detection of a burst
  71. GRB 250625A: Swift-BAT refined analysis
  72. GRB 250625A: Leavitt Observatory afterglow detection
  73. Fermi Gamma-ray Burst Monitor trigger 772732642/250627665 is not a GRB
  74. Fermi Gamma-ray Burst Monitor trigger 772720540/250627525 is not a GRB
  75. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  76. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  77. GRB 250626A: Fermi GBM Final Real-time Localization
  78. Fermi Gamma-ray Burst Monitor trigger 772647532/250626680 is not a GRB
  79. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  80. GRB 250625A: SVOM/C-GFT upper limit in early phase
  81. GRB 250625A: GECAM-B detection
  82. GRB 250625A: Swift/UVOT Upper Limits
  83. GRB 250625A: ABObservatory afterglow detection
  84. GRB 250625A: OHP/T193 optical detection
  85. GRB 250625A: COLIBRÍ optical observations
  86. GRB 250625A: Fermi-LAT detection
  87. GRB 250625A: Swift-XRT refined Analysis
  88. GRB 250625A: JinShan optical observations
  89. GRB250625A: Fermi GBM Observation
  90. Swift GRB 250625A: Global MASTER-Net observations report
  91. GRB 250625A: NOT z-band upper limit
  92. GRB 250625A: SVOM/VT optical confirmation
  93. GRB 250620B: Fermi GBM Observation
  94. GRB 250625A: SAO RAS possible optical afterglow
  95. GRB 250625A: Enhanced Swift-XRT position
  96. Fermi GRB 250625A: Global MASTER-Net observations report
  97. GRB 250625A: Swift detection of a burst
  98. GRB 250625A: Fermi GBM Final Real-time Localization
  99. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  100. GRB 250620A: AstroSat CZTI detection

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