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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"

27548 results found.

  1. GRB 250706A: SAO RAS optical observations
  2. EP250704A: NOWT Detection
  3. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  4. GRB250706B: Swift-XRT counterpart detection
  5. GRB 250706B: iTelescope optical observations
  6. IceCube-250706A - IceCube observation of a high-energy neutrino candidate track-like event
  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. GRB 250703A: EIRSAT-1 GMOD Detection
  17. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  18. GRB 250704B: Swift/UVOT Upper Limits
  19. GRB 250704A: Swift/UVOT Detection
  20. GRB 250704B: Insight-HXMT detection
  21. Konus-Wind detection of GRB 250703A
  22. IPN triangulation of GRB 250703A
  23. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  24. Konus-Wind detection of short/hard GRB 250704B/ EP250704a
  25. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  26. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  27. GRB 250702F: Kilonova-Catcher optical afterglow detection
  28. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  29. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  30. EP250704a / GRB 250704B: JinShan optical observations
  31. GRB 250704A: SVOM/VT optical observation
  32. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  33. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  34. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  35. EP 250704a: BOOTES-5 optical detection
  36. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  37. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  38. GRB 250702A: Insight-HXMT detection
  39. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  40. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  41. EP250704a / GRB250704B: Swift-XRT counterpart detection
  42. GRB 250704A: Swift-XRT afterglow detection
  43. GRB 250702B / EP2050702a: FTW optical and NIR observations
  44. Konus-Wind detection of GRB 250702F
  45. EP250704a / GRB 250704B - REM observations
  46. GRB 250702F: GROWTH-India Telescope optical observations
  47. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  48. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  49. EP250702a: WFST optical observations
  50. EP250704a: Einstein Probe detection of an X-ray transient
  51. GRB 250702F: optical photometry from Konkoly
  52. GRB 250704A: REM detection of the optical afterglow
  53. GRB 250702F: SVOM/VT optical observation
  54. GRB 250704A: SVOM detection of a burst
  55. GRB 250702F: Swift/UVOT Detection
  56. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  57. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  58. GRB 250702F: Swift-XRT refined Analysis
  59. GRB 250702F: Leavitt Observatory optical observations
  60. GRB 250702F: AKO Optical Afterglow Detection
  61. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  62. GRB 250702A: GECAM-B detection
  63. GRB 250702F: Skynet Optical Observations
  64. GRB 250424A: VIRT Optical Upper Limit
  65. GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
  66. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  67. GRB 250702F: TRT Optical Observation
  68. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  69. GRB 250702F: REM optical afterglow detection
  70. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  71. GRB 250703A: Fermi GBM Final Real-time Localization
  72. GRB 250702F: COLIBRÍ Observations of the Afterglow
  73. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  74. GRB 250702F: Enhanced Swift-XRT position
  75. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  76. GRB 250702F: NOT observations of the optical afterglow
  77. GRB 250702F: MASTER optical afterglow observation
  78. GRB 250702F: GOTO optical counterpart detection
  79. GRB 250702F: Ondrejov D50 optical afterglow detection
  80. GRB 250702F: Swift detection of a burst with an optical counterpart
  81. GRB 250702F: Fermi GBM Final Real-time Localization
  82. GRB 250702E: Fermi GBM Final Real-time Localization
  83. Konus-Wind detection of GRB 250627A
  84. IPN triangulation of GRB 250627A (short)
  85. GRB 250702A: Fermi GBM Detection
  86. GRB 250702D: Fermi GBM Final Localization Correction
  87. GRB 250702C: Fermi GBM Final Real-time Localization
  88. GRB 250702B: Fermi GBM Final Real-time Localization
  89. GRB 250702A: Fermi GBM Final Real-time Localization
  90. GRB 250628B: Swift-XRT observations
  91. GRB 250628B: SVOM/VT optical upper limit
  92. GRB 250628B: EP-FXT counterpart detection
  93. GRB 250627A: Insight-HXMT detection
  94. GRB 250627A: SVOM/GRM detection of a short burst
  95. GRB 250628A: REM optical/NIR upper limits
  96. GRB 250628C: Fermi GBM Final Real-time Localization
  97. GRB 250628B: SVOM detection of a long burst
  98. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  99. GRB 250628A: VLT/X-shooter upper limits
  100. GRB 250628A: Swift/UVOT Upper Limits

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