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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"

16159 results found.

  1. GRB 250706A: Swift detection of a burst
  2. GRB 250704B: Swift-XRT refined Analysis
  3. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  4. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  5. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  6. GRB 250704B: Swift/UVOT Upper Limits
  7. GRB 250704A: Swift/UVOT Detection
  8. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  9. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  10. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  11. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  12. GRB 250702F: Kilonova-Catcher optical afterglow detection
  13. GRB 250702F: Monte Agliale Observatory optical observations
  14. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  15. EP250704a / GRB 250704B: JinShan optical observations
  16. EP250704a / GRB 250704B: SAO RAS optical observations
  17. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  18. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  19. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  20. GRB 250704A: Swift-XRT afterglow detection
  21. EP250704a / GRB 250704B - REM observations
  22. GRB 250702F: GROWTH-India Telescope optical observations
  23. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  24. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  25. EP250702a: WFST optical observations
  26. EP250704a: COLIBRÍ optical counterpart candidate
  27. EP250704a: Einstein Probe detection of an X-ray transient
  28. GRB 250704A: REM detection of the optical afterglow
  29. GRB 250704A: SVOM detection of a burst
  30. GRB 250702F: Swift/UVOT Detection
  31. GRB 250702F: Leavitt Observatory optical observations
  32. GRB 250702F: AKO Optical Afterglow Detection
  33. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  34. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  35. GRB 250702F: Skynet Optical Observations
  36. GRB 250424A: VIRT Optical Upper Limit
  37. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  38. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  39. GRB 250702F: TRT Optical Observation
  40. GRB 250703A: DDOTI Optical Upper Limit
  41. GRB 250702F: REM optical afterglow detection
  42. GRB 250702F: DDOTI Optical Observation
  43. GRB 250702F: COLIBRÍ Observations of the Afterglow
  44. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  45. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  46. GRB 250702F: Enhanced Swift-XRT position
  47. GRB 250702F: NOT observations of the optical afterglow
  48. GRB 250702F: Swift detection of a burst with an optical counterpart
  49. GRB 250702A: Fermi GBM Detection
  50. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  51. GRB 250628B: EP-FXT counterpart detection
  52. GRB 250628A: REM optical/NIR upper limits
  53. GRB 250628A: VLT/X-shooter upper limits
  54. GRB 250628A: Swift/UVOT Upper Limits
  55. GRB 250628A: Enhanced Swift-XRT position
  56. GRB 250628A: Swift detection of a burst
  57. GRB 250625A: Leavitt Observatory afterglow detection
  58. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  59. The EP-WXT trigger 01709179435 is likely a new outburst of the CV SS Cyg
  60. GRB 250625A: SVOM/C-GFT upper limit in early phase
  61. GRB 250625A: Swift/UVOT Upper Limits
  62. GRB 250625A: ABObservatory afterglow detection
  63. GRB 250625A: OHP/T193 optical detection
  64. GRB 250625A: COLIBRÍ optical observations
  65. GRB 250625A: JinShan optical observations
  66. GRB 250625A: SAO RAS possible optical afterglow
  67. GRB 250625A: Enhanced Swift-XRT position
  68. GRB 250625A: Swift detection of a burst
  69. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  70. The EP-WXT trigger 01709179396 is likely a flaring star CSTAR 38580
  71. GRB 241018A: Maidanak optical observations
  72. IPN triangulation of GRB 250620С (long/bright)
  73. GRB 250620C: SVOM/GRM observation
  74. GRB 250620A: SVOM/GRM observation of a short burst
  75. GRB250620A: Fermi GBM Observation
  76. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  77. GRB 250619B: Fermi GBM Observation
  78. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  79. The EP-WXT trigger 01709179071 is likely a flaring star
  80. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  81. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  82. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  83. GRB 250617B: Nickel telescope optical observations
  84. GRB 250615A: Kilonova-Catcher optical upper limits
  85. GRB 250617B: Assy AZT-20 Optical Observations
  86. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  87. GRB 250617B: Swift/UVOT Detection
  88. GRB 250617B: Kilonova-Catcher optical afterglow detection
  89. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  90. GRB 250617B: COLIBRÍ optical observations
  91. GRB 250617B: NOT NIR observations of the afterglow
  92. GRB 250617B: NUTTelA-TAO early time optical observations
  93. GRB 250617B: Enhanced Swift-XRT position
  94. The EP-WXT trigger 01709178990 is likely a flaring star
  95. GRB 250617B: SAO RAS optical observations
  96. GRB 250617B: Swift detection of a burst with an optical counterpart
  97. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  98. EP-WXT trigger 01709178975: GOTO optical upper limit
  99. The EP-WXT trigger 01709178975 is likely a flaring star
  100. SVOM sb25061207: AbAO AS-32 Optical Upper Limit

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