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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"

18133 results found.

  1. IceCube-250706A: COLIBRÍ optical upper limits
  2. GRB 250706A: JinShan optical upper limits
  3. GRB 250706A: SAO RAS optical observations
  4. EP250704A: NOWT Detection
  5. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  6. GRB 250706B: iTelescope optical observations
  7. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  8. GRB 250706B: SVOM/VT optical observation
  9. GRB 250706B: TRT bright optical counterpart detection
  10. GRB 250706A: GROWTH-India Telescope optical upper limit
  11. GRB 250706B: SVOM detection of a long burst
  12. GRB 250706A: Swift detection of a burst
  13. GRB 250704B: Swift-XRT refined Analysis
  14. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  15. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  16. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  17. GRB 250704B: Swift/UVOT Upper Limits
  18. GRB 250704A: Swift/UVOT Detection
  19. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  20. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  21. Konus-Wind detection of short/hard GRB 250704B/ EP250704a
  22. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  23. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  24. GRB 250702F: Kilonova-Catcher optical afterglow detection
  25. GRB 250702F: Monte Agliale Observatory optical observations
  26. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  27. EP250704a / GRB 250704B: JinShan optical observations
  28. EP250704a / GRB 250704B: SAO RAS optical observations
  29. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  30. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  31. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  32. GRB 250704A: Swift-XRT afterglow detection
  33. EP250704a / GRB 250704B - REM observations
  34. GRB 250702F: GROWTH-India Telescope optical observations
  35. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  36. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  37. EP250702a: WFST optical observations
  38. EP250704a: COLIBRÍ optical counterpart candidate
  39. EP250704a: Einstein Probe detection of an X-ray transient
  40. GRB 250704A: REM detection of the optical afterglow
  41. GRB 250704A: SVOM detection of a burst
  42. GRB 250702F: Swift/UVOT Detection
  43. GRB 250702F: Leavitt Observatory optical observations
  44. GRB 250702F: AKO Optical Afterglow Detection
  45. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  46. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  47. GRB 250702F: Skynet Optical Observations
  48. GRB 250424A: VIRT Optical Upper Limit
  49. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  50. GRB 250702F: TRT Optical Observation
  51. GRB 250703A: DDOTI Optical Upper Limit
  52. GRB 250702F: REM optical afterglow detection
  53. GRB 250702F: DDOTI Optical Observation
  54. GRB 250702F: COLIBRÍ Observations of the Afterglow
  55. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  56. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  57. GRB 250702F: Enhanced Swift-XRT position
  58. GRB 250702F: NOT observations of the optical afterglow
  59. GRB 250702F: Swift detection of a burst with an optical counterpart
  60. Swift GRB 250702F: Global MASTER-Net observations report
  61. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  62. GRB 250628A: REM optical/NIR upper limits
  63. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  64. GRB 250628A: VLT/X-shooter upper limits
  65. GRB 250628A: Swift/UVOT Upper Limits
  66. GRB 250628A: Enhanced Swift-XRT position
  67. GRB 250628A: Swift detection of a burst
  68. GRB 250625A: Leavitt Observatory afterglow detection
  69. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  70. GRB 250625A: SVOM/C-GFT upper limit in early phase
  71. GRB 250625A: Swift/UVOT Upper Limits
  72. GRB 250625A: ABObservatory afterglow detection
  73. GRB 250625A: OHP/T193 optical detection
  74. GRB 250625A: COLIBRÍ optical observations
  75. GRB 250625A: JinShan optical observations
  76. GRB 250625A: SAO RAS possible optical afterglow
  77. GRB 250625A: Enhanced Swift-XRT position
  78. GRB 250625A: Swift detection of a burst
  79. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  80. GRB 250620A: AstroSat CZTI detection
  81. The EP-WXT trigger 01709179396 is likely a flaring star CSTAR 38580
  82. GRB 241018A: Maidanak optical observations
  83. IPN triangulation of GRB 250620С (long/bright)
  84. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  85. GRB 250620C: SVOM/GRM observation
  86. GRB 250620A: SVOM/GRM observation of a short burst
  87. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  88. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  89. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  90. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  91. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  92. GRB 250617B: Nickel telescope optical observations
  93. GRB 250615A: Kilonova-Catcher optical upper limits
  94. GRB 250617B: Assy AZT-20 Optical Observations
  95. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  96. GRB 250617B: Swift/UVOT Detection
  97. GRB 250617B: Kilonova-Catcher optical afterglow detection
  98. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  99. GRB 250617B: COLIBRÍ optical observations
  100. GRB 250617B: NOT NIR observations of the afterglow

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