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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"

16785 results found.

  1. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  2. GRB 250702F: radio detection with the VLA
  3. IceCube-250706A: EP-FXT follow-up observations
  4. GRB 250706B/C: Fermi-LAT detection
  5. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  6. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  7. GRB 250706B: Swift/UVOT Detection
  8. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  9. GRB 250702F: GRANDMA observations
  10. GRB 250706A: Swift/UVOT Upper Limits
  11. GRB 250706B: REM optical observations
  12. GRB 250706A: REM optical/NIR observations
  13. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  14. IceCube-250416A: DDOTI Optical Upper Limit
  15. IceCube-250706A: COLIBRÍ optical upper limits
  16. GRB 250706A: JinShan optical upper limits
  17. GRB 250706A: SAO RAS optical observations
  18. EP250704A: NOWT Detection
  19. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  20. The EP-WXT trigger 01709181580 is likely a flaring star
  21. GRB 250706B: iTelescope optical observations
  22. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  23. GRB 250706B: SVOM/VT optical observation
  24. GRB 250706B: TRT bright optical counterpart detection
  25. GRB 250706A: GROWTH-India Telescope optical upper limit
  26. GRB 250706B: SVOM detection of a long burst
  27. GRB 250706A: Swift detection of a burst
  28. GRB 250704B: Swift-XRT refined Analysis
  29. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  30. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  31. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  32. GRB 250704B: Swift/UVOT Upper Limits
  33. GRB 250704A: Swift/UVOT Detection
  34. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  35. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  36. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  37. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  38. GRB 250702F: Kilonova-Catcher optical afterglow detection
  39. GRB 250702F: Monte Agliale Observatory optical observations
  40. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  41. EP250704a / GRB 250704B: JinShan optical observations
  42. EP250704a / GRB 250704B: SAO RAS optical observations
  43. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  44. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  45. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  46. GRB 250704A: Swift-XRT afterglow detection
  47. EP250704a / GRB 250704B - REM observations
  48. GRB 250702F: GROWTH-India Telescope optical observations
  49. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  50. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  51. EP250702a: WFST optical observations
  52. EP250704a: COLIBRÍ optical counterpart candidate
  53. EP250704a: Einstein Probe detection of an X-ray transient
  54. GRB 250704A: REM detection of the optical afterglow
  55. GRB 250704A: SVOM detection of a burst
  56. GRB 250702F: Swift/UVOT Detection
  57. GRB 250702F: Leavitt Observatory optical observations
  58. GRB 250702F: AKO Optical Afterglow Detection
  59. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  60. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  61. GRB 250702F: Skynet Optical Observations
  62. GRB 250424A: VIRT Optical Upper Limit
  63. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  64. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  65. GRB 250702F: TRT Optical Observation
  66. GRB 250703A: DDOTI Optical Upper Limit
  67. GRB 250702F: REM optical afterglow detection
  68. GRB 250702F: DDOTI Optical Observation
  69. GRB 250702F: COLIBRÍ Observations of the Afterglow
  70. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  71. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  72. GRB 250702F: Enhanced Swift-XRT position
  73. GRB 250702F: NOT observations of the optical afterglow
  74. GRB 250702F: Swift detection of a burst with an optical counterpart
  75. GRB 250702A: Fermi GBM Detection
  76. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  77. GRB 250628B: EP-FXT counterpart detection
  78. GRB 250628A: REM optical/NIR upper limits
  79. GRB 250628A: VLT/X-shooter upper limits
  80. GRB 250628A: Swift/UVOT Upper Limits
  81. GRB 250628A: Enhanced Swift-XRT position
  82. GRB 250628A: Swift detection of a burst
  83. GRB 250625A: Leavitt Observatory afterglow detection
  84. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  85. The EP-WXT trigger 01709179435 is likely a new outburst of the CV SS Cyg
  86. GRB 250625A: SVOM/C-GFT upper limit in early phase
  87. GRB 250625A: Swift/UVOT Upper Limits
  88. GRB 250625A: ABObservatory afterglow detection
  89. GRB 250625A: OHP/T193 optical detection
  90. GRB 250625A: COLIBRÍ optical observations
  91. GRB 250625A: JinShan optical observations
  92. GRB 250625A: SAO RAS possible optical afterglow
  93. GRB 250625A: Enhanced Swift-XRT position
  94. GRB 250625A: Swift detection of a burst
  95. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  96. The EP-WXT trigger 01709179396 is likely a flaring star CSTAR 38580
  97. GRB 241018A: Maidanak optical observations
  98. IPN triangulation of GRB 250620С (long/bright)
  99. GRB 250620C: SVOM/GRM observation
  100. GRB 250620A: SVOM/GRM observation of a short burst

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