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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"

3868 results found.

  1. GRB 250716A: Fermi GBM Final Real-time Localization
  2. GRB 250706B/C: 7DT Follow-up Observations
  3. Fermi GRB 250711A: Global MASTER-Net observations report
  4. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  5. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  6. IceCube-250706A: Global MASTER-Net observations report
  7. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  8. GRB 250702F: Fermi GBM Observation
  9. GRB 250702F: Leavitt Observatory optical observations
  10. EP250702a: Global MASTER-Net observations report
  11. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  12. Fermi GRB 250702F: Global MASTER-Net observations report
  13. Fermi GRB 250702C: Global MASTER-Net observations report
  14. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  15. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  16. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  17. GRB 250628B: SVOM detection of a long burst
  18. Fermi GRB 250626A: Global MASTER-Net observations report
  19. GRB 250625A: Leavitt Observatory afterglow detection
  20. Fermi trigger No 772190032: Global MASTER-Net observations report
  21. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  22. GRB 250619B: Fermi GBM Observation
  23. GRB 250615A/EP250615a: FTW optical and NIR observations
  24. GRB 250617B: Ondrejov D50 optical afterglow detection
  25. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  26. Fermi trigger No 771424081: Global MASTER-Net observations report
  27. EP250612a: Global MASTER-Net observations report
  28. EP250610a: SVOM/VT optical upper limit
  29. Fermi trigger No 771072240: Global MASTER-Net observations report
  30. GRB 250608A: SVOM/GRM detection of a possible magnetar X-ray burst
  31. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  32. Fermi trigger No 770867684: Global MASTER-Net observations report
  33. Konus-Wind detection of GRB 250601A
  34. GRB 250601A: Fermi GBM Observation
  35. Fermi GRB 250601A: Global MASTER-Net observations report
  36. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  37. GRB 250601A: Fermi GBM Final Real-time Localization
  38. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  39. GRB 250530A: SVOM/VT optical upper limit
  40. GRB 250529B: Fermi GBM Final Real-time Localization
  41. GRB 250529A: Fermi GBM Final Real-time Localization
  42. GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
  43. Fermi GRB 250522B: Global MASTER-Net observations report
  44. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  45. Konus-Wind detection of GRB 250516A
  46. GRB 250515A: NOT classification of GOTO25cqo as a type-Ia SN
  47. GRB 250516A: Swift detection of a burst
  48. GRB 250516A: Fermi GBM Final Real-time Localization
  49. GRB 250507B: AstroSat CZTI detection
  50. Fermi GRB 250510C: Global MASTER-Net observations report
  51. Fermi GRB 250510B: Global MASTER-Net observations report
  52. GRB 250509A: Fermi GBM Final Real-time Localization
  53. GRB 250506A: NOT optical upper limits
  54. GRB 250506A: Swift XRT observations and possible counterpart detection
  55. GRB 250506A: TRT optical observations
  56. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
  57. GRB 250504A: MeerLICHT optical afterglow detection
  58. Fermi GRB 250504A: Global MASTER-Net observations report
  59. Swift GRB250504.98: Global MASTER-Net observations report
  60. Fermi-LAT Gamma-ray Observations of IceCube-250429A
  61. GRB 250430A: Leavitt Observatory optical upper limit
  62. GRB 250430A : MITSuME Akeno optical upper limits
  63. IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
  64. GRB 250430A: AKO Optical Afterglow Detection
  65. Swift GRB250430.73: Global MASTER-Net observations report
  66. EP250427a/GRB250427A: HCT optical follow-up
  67. EP250428b: SVOM/VT upper limit
  68. EP250428b: SAO RAS optical upper limit
  69. EP250428b: LAST optical upper limit
  70. IceCube-250429A - IceCube observation of a high-energy neutrino candidate track-like event
  71. EP250428b: Global MASTER-Net observations report
  72. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  73. EP250427a: TRT optical counterpart detection
  74. EP 250427a: BOOTES-7 optical afterglow candidate
  75. GRB 250424A: SVOM/VT optical observation
  76. GRB 250419A: Mondy Optical Observations
  77. GRB 250424A: Swift/UVOT Detection
  78. GRB250419A: VLA radio detection
  79. GRB 250419A: Mephisto Multi-band Optical Detection
  80. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  81. GRB 250419A: Optical Observations via Virtual Telescope Project
  82. IceCube Alert 250421.71: Global MASTER-Net observations report
  83. EP250421a: JinShan likely optical counterpart
  84. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  85. GRB 250419A: Swift/UVOT Follow up
  86. GRB 250419A: AKO Optical Afterglow Detection
  87. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  88. GRB 250419A: SVOM detection of a soft burst
  89. GRB 250412A: AstroSat CZTI detection
  90. EP250404a: Nanshan 0.43m Telescope optical observatios
  91. Fermi trigger No 766148493: Global MASTER-Net observations report
  92. Fermi trigger No 766173972: Global MASTER-Net observations report
  93. Fermi GRB 250407A: Global MASTER-Net observations report
  94. Fermi GRB 250406A: Global MASTER-Net observations report
  95. GRB 250402A: Mondy optical observations
  96. EP250402a: Einstein Probe detection of a fast X-ray transient
  97. Fermi GRB 250331E: Global MASTER-Net observations report
  98. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  99. IceCube-250330A: Upper limits from a search for additional neutrino events in IceCube
  100. SVOM/sb25033102: SVOM detection of an X-ray transient

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