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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"

14345 results found.

  1. GRB 250706B/C: Fermi-LAT detection
  2. GRB 250706B: Swift/UVOT Detection
  3. GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
  4. GRB 250702F: GRANDMA observations
  5. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  6. IceCube-250416A: DDOTI Optical Upper Limit
  7. GRB 250706A: JinShan optical upper limits
  8. GRB 250706A: SAO RAS optical observations
  9. EP250704A: NOWT Detection
  10. GRB250706B: Swift-XRT counterpart detection
  11. IceCube-250706A - IceCube observation of a high-energy neutrino candidate track-like event
  12. GRB 250706B: TRT bright optical counterpart detection
  13. GRB 250706B: SVOM detection of a long burst
  14. GRB 250706A: Swift detection of a burst
  15. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  16. GRB 250703A: EIRSAT-1 GMOD Detection
  17. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  18. GRB 250704A: Swift/UVOT Detection
  19. GRB 250704B: Insight-HXMT detection
  20. Konus-Wind detection of GRB 250703A
  21. IPN triangulation of GRB 250703A
  22. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  23. Konus-Wind detection of short/hard GRB 250704B/ EP250704a
  24. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  25. GRB 250702F: Kilonova-Catcher optical afterglow detection
  26. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  27. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  28. EP250704a / GRB 250704B: JinShan optical observations
  29. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  30. EP 250704a: BOOTES-5 optical detection
  31. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  32. GRB 250702A: Insight-HXMT detection
  33. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  34. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  35. EP250704a / GRB250704B: Swift-XRT counterpart detection
  36. GRB 250704A: Swift-XRT afterglow detection
  37. Konus-Wind detection of GRB 250702F
  38. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  39. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  40. EP250702a: WFST optical observations
  41. EP250704a: Einstein Probe detection of an X-ray transient
  42. GRB 250702F: optical photometry from Konkoly
  43. GRB 250704A: REM detection of the optical afterglow
  44. GRB 250704A: SVOM detection of a burst
  45. GRB 250702F: Swift/UVOT Detection
  46. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  47. GRB 250702F: AKO Optical Afterglow Detection
  48. GRB 250702A: GECAM-B detection
  49. GRB 250702F: Skynet Optical Observations
  50. GRB 250424A: VIRT Optical Upper Limit
  51. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  52. GRB 250702F: TRT Optical Observation
  53. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  54. GRB 250702F: REM optical afterglow detection
  55. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  56. GRB 250703A: Fermi GBM Final Real-time Localization
  57. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  58. GRB 250702F: GOTO optical counterpart detection
  59. GRB 250702F: Ondrejov D50 optical afterglow detection
  60. GRB 250702F: Swift detection of a burst with an optical counterpart
  61. GRB 250702F: Fermi GBM Final Real-time Localization
  62. GRB 250702E: Fermi GBM Final Real-time Localization
  63. Konus-Wind detection of GRB 250627A
  64. IPN triangulation of GRB 250627A (short)
  65. GRB 250702A: Fermi GBM Detection
  66. GRB 250702D: Fermi GBM Final Localization Correction
  67. GRB 250702C: Fermi GBM Final Real-time Localization
  68. GRB 250702B: Fermi GBM Final Real-time Localization
  69. GRB 250702A: Fermi GBM Final Real-time Localization
  70. GRB 250628B: EP-FXT counterpart detection
  71. GRB 250627A: Insight-HXMT detection
  72. GRB 250627A: SVOM/GRM detection of a short burst
  73. GRB 250628C: Fermi GBM Final Real-time Localization
  74. GRB 250628B: SVOM detection of a long burst
  75. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  76. GRB 250628A: VLT/X-shooter upper limits
  77. GRB 250628A: Swift detection of a burst
  78. GRB 250625A: Leavitt Observatory afterglow detection
  79. GRB 250626A: Fermi GBM Final Real-time Localization
  80. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  81. GRB 250625A: GECAM-B detection
  82. GRB 250625A: ABObservatory afterglow detection
  83. GRB 250625A: OHP/T193 optical detection
  84. GRB 250625A: COLIBRÍ optical observations
  85. GRB 250625A: Fermi-LAT detection
  86. GRB 250625A: JinShan optical observations
  87. GRB 250625A: Swift detection of a burst
  88. GRB 250625A: Fermi GBM Final Real-time Localization
  89. GRB 250620A: AstroSat CZTI detection
  90. GRB 241018A: Maidanak optical observations
  91. GRB 250620C: AstroSat CZTI detection
  92. GRB 250624A: Fermi GBM Final Real-time Localization
  93. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
  94. GRB 250623A: Fermi GBM Final Real-time Localization
  95. GRB 250521A: VZLUSAT-2 detection
  96. Konus-Wind detection of GRB 250620C
  97. IPN triangulation of GRB 250620C (long/bright)
  98. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  99. GRB 250621A: Fermi GBM Final Real-time Localization
  100. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst

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