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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"

32796 results found.

  1. GRB 250702F: TRT Optical Observation
  2. GRB 250703A: DDOTI Optical Upper Limit
  3. GRB 250702F: REM optical afterglow detection
  4. GRB 250702F: DDOTI Optical Observation
  5. GRB 250702B,C,D,E / EP 250702: MAXI/GSC detection
  6. GRB 250703A: Fermi GBM Final Real-time Localization
  7. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  8. GRB 250702F: COLIBRÍ Observations of the Afterglow
  9. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  10. Fermi GRB 250702E: Global MASTER-Net observations report
  11. Fermi GRB 250702B: Global MASTER-Net observations report
  12. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  13. GRB 250702F: Enhanced Swift-XRT position
  14. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  15. GRB 250702F: NOT observations of the optical afterglow
  16. GRB 250702F: MASTER optical afterglow observation
  17. Fermi GRB 250702F: Global MASTER-Net observations report
  18. Fermi GRB 250702C: Global MASTER-Net observations report
  19. GRB 250702F: GOTO optical counterpart detection
  20. GRB 250702F: Ondrejov D50 optical afterglow detection
  21. GRB 250702F: Swift detection of a burst with an optical counterpart
  22. GRB 250702F: Fermi GBM Final Real-time Localization
  23. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  24. GRB 250702E: Fermi GBM Final Real-time Localization
  25. Konus-Wind detection of GRB 250627A
  26. IPN triangulation of GRB 250627A (short)
  27. GRB 250702A: Fermi GBM Detection
  28. GRB 250702D: Fermi GBM Final Localization Correction
  29. GRB 250702C: Fermi GBM Final Real-time Localization
  30. GRB 250702B: Fermi GBM Final Real-time Localization
  31. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  32. GRB 250702A: Fermi GBM Final Real-time Localization
  33. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  34. GRB 250628B: Swift-XRT observations
  35. Fermi Gamma-ray Burst Monitor trigger 772981768/250630548 is not a GRB
  36. GRB 250628B: SVOM/VT optical upper limit
  37. GRB 250628B: EP-FXT counterpart detection
  38. GRB 250627A: Insight-HXMT detection
  39. GRB 250627A: SVOM/GRM detection of a short burst
  40. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate (duplicate submission)
  41. GRB 250628A: REM optical/NIR upper limits
  42. GRB 250628C: Fermi GBM Final Real-time Localization
  43. GRB 250628B: SVOM detection of a long burst
  44. Fermi Gamma-ray Burst Monitor trigger 772811638/250628579 is not a GRB
  45. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  46. GRB 250628A: VLT/X-shooter upper limits
  47. GRB 250628A: Swift/UVOT Upper Limits
  48. GRB 250628A: Swift-XRT refined Analysis
  49. Fermi GRB 250626A: Global MASTER-Net observations report
  50. Swift GRB 250628A: Global MASTER-Net observations report
  51. GRB 250628A: Enhanced Swift-XRT position
  52. GRB 250628A: Swift detection of a burst
  53. GRB 250625A: Swift-BAT refined analysis
  54. GRB 250625A: Leavitt Observatory afterglow detection
  55. Fermi Gamma-ray Burst Monitor trigger 772732642/250627665 is not a GRB
  56. Fermi Gamma-ray Burst Monitor trigger 772720540/250627525 is not a GRB
  57. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  58. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  59. GRB 250626A: Fermi GBM Final Real-time Localization
  60. Fermi Gamma-ray Burst Monitor trigger 772647532/250626680 is not a GRB
  61. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  62. GRB 250625A: SVOM/C-GFT upper limit in early phase
  63. GRB 250625A: GECAM-B detection
  64. GRB 250625A: Swift/UVOT Upper Limits
  65. GRB 250625A: ABObservatory afterglow detection
  66. GRB 250625A: OHP/T193 optical detection
  67. GRB 250625A: COLIBRÍ optical observations
  68. GRB 250625A: Fermi-LAT detection
  69. GRB 250625A: Swift-XRT refined Analysis
  70. GRB 250625A: JinShan optical observations
  71. GRB250625A: Fermi GBM Observation
  72. Swift GRB 250625A: Global MASTER-Net observations report
  73. GRB 250625A: NOT z-band upper limit
  74. GRB 250625A: SVOM/VT optical confirmation
  75. GRB 250620B: Fermi GBM Observation
  76. GRB 250625A: SAO RAS possible optical afterglow
  77. GRB 250625A: Enhanced Swift-XRT position
  78. Fermi GRB 250625A: Global MASTER-Net observations report
  79. GRB 250625A: Swift detection of a burst
  80. GRB 250625A: Fermi GBM Final Real-time Localization
  81. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  82. GRB 250620A: AstroSat CZTI detection
  83. GRB 241018A: Maidanak optical observations
  84. GRB 250620C: AstroSat CZTI detection
  85. Fermi GRB 250624A: Global MASTER-Net observations report
  86. GRB 250624A: Fermi GBM Final Real-time Localization
  87. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
  88. Fermi GRB 250623A: Global MASTER-Net observations report
  89. GRB 250623A: Fermi GBM Final Real-time Localization
  90. GRB 250521A: VZLUSAT-2 detection
  91. GRB 250617B: Swift-BAT refined analysis
  92. Konus-Wind detection of GRB 250620C
  93. IPN triangulation of GRB 250620С (long/bright)
  94. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  95. GRB 250620C: SVOM/GRM observation
  96. GRB 250620A: SVOM/GRM observation of a short burst
  97. GRB250620A: Fermi GBM Observation
  98. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  99. Fermi GRB 250621A: Global MASTER-Net observations report
  100. GRB 250619B: Fermi GBM Observation

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