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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"

11100 results found.

  1. EP250404a: Nanshan/HMT optical counterpart detection
  2. EP250404a: Einstein Probe detection of an X-ray transient
  3. GRB 250404A: Fermi GBM Final Real-time Localization
  4. GRB 250403A: Swift/UVOT Detection
  5. GRB 250403A: SVOM/VT optical observation
  6. GRB 250403A: REM NIR afterglow detection
  7. GRB 250403A: LCO optical counterpart detection
  8. GRB 250403A: JinShan optical observations
  9. GRB 250403A: Optical counterpart detection by LCO.
  10. GRB 250403A: Swift-XRT observations
  11. Fermi GRB 250403A: Global MASTER-Net observations report
  12. GRB 250403A: GOTO optical counterpart follow-up observations
  13. GRB 250403A: GMG Optical Observation
  14. GRB 250403A: 1.6m Mephisto multi-band optical detection
  15. GRB 250402A: Fermi GBM Observation
  16. GRB 250403A: SVOM/C-GFT optical observations
  17. GRB 250403A: GOTO detection of the optical afterglow
  18. GRB 250403A : SVOM detection of a burst
  19. GRB 250403A: Fermi GBM Final Real-time Localization
  20. GRB 250331E: SVOM/GRM observation
  21. GRB250331D: AbAO optical observations
  22. GRB 250331D: Fermi GBM observation
  23. GRB 250330B: SVOM/GRM observation of a short burst
  24. Fermi GRB 250331E: Global MASTER-Net observations report
  25. Fermi GRB 250331D: Global MASTER-Net observations report
  26. GRB 250330B: EIRSAT-1 GMOD Detection
  27. GRB 250331E: Fermi GBM Final Real-time Localization
  28. Fermi trigger No 765078057: Global MASTER-Net observations report
  29. GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
  30. Fermi-LAT gamma-ray observations of IceCube-250330A
  31. GRB 250330A: Fermi GBM Observation
  32. GRB 250331D: Fermi GBM Final Real-time Localization
  33. Fermi GRB 250330B: Global MASTER-Net observations report
  34. GRB 250330B: Fermi GBM Final Real-time Localization
  35. Fermi GRB 250330A: Global MASTER-Net observations report
  36. GRB 250330A: BOOTES-7 early optical upper limit
  37. GRB 250330A: Fermi GBM Final Localization
  38. IceCube-250330A - IceCube observation of a high-energy neutrino candidate track-like event
  39. GRB 250330A: Swift detection of a burst
  40. GRB 250327B: CrAO and SAO RAS Optical Observations
  41. GRB 250327A: SVOM/VT upper limits on the XRT position
  42. GRB 250327A: J-band observations with WINTER
  43. GRB 250327A: SVOM/VT optical candidate
  44. GRB 250327A: Fermi GBM observation
  45. Fermi GRB 250327A: Global MASTER-Net observations report
  46. GRB 250327A: DDOTI Optical Observations
  47. GRB 250327A: COLIBRÍ optical upper limit
  48. GRB 250327A: Fermi GBM Final Real-time Localization
  49. Fermi trigger No 764700395: Global MASTER-Net observations report
  50. GRB 250225B: GECAM-A detection
  51. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  52. GRB 250321C: Fermi GBM Final Real-time Localization
  53. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  54. GRB 250320B: Fermi GBM Observation
  55. GRB 250320B: Fermi-LAT detection
  56. GRB 250320B: SVOM/GRM observation of a long burst
  57. GRB 250320B: AstroSat CZTI detection
  58. Fermi GRB 250320B: Global MASTER-Net observations report
  59. Fermi GRB 250321A: Global MASTER-Net observations report
  60. GRB 250321A: GOTO optical upper limits
  61. EP250226a/GRB 250226A: KAIT optical observations
  62. GRB 250321A: Fermi GBM Observation
  63. GRB 250321A: Swift detection of a burst
  64. GRB 250321A: Fermi GBM Final Real-time Localization
  65. GRB 250320B: Fermi GBM Final Real-time Localization
  66. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  67. GRB 250320A: Fermi GBM Final Real-time Localization
  68. Fermi GRB 250319B: Global MASTER-Net observations report
  69. GRB 250313A: GRBAlpha detection
  70. GRB 250319B: Fermi GBM Final Localization
  71. GRB 250319A: Fermi GBM Final Localization
  72. GRB 250317D: EIRSAT-1 GMOD Detection
  73. Fermi trigger No 763933627: Global MASTER-Net observations report
  74. GRB 250316A: Swift/UVOT Upper Limits
  75. GRB 250316A: AbAO AS-32 Optical Upper Limit
  76. GRB 250316A: Fermi GBM Observation
  77. Fermi trigger No 763862734: Global MASTER-Net observations report
  78. GRB 250317A: Fermi GBM Final Real-time Localization
  79. Fermi GRB 250316A: Global MASTER-Net observations report
  80. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  81. GRB 250316A: Fermi GBM Final Real-time Localization
  82. GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
  83. GRB 250312B: GRBAlpha detection
  84. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  85. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  86. GRB 250313A: Fermi GBM Detection
  87. GRB 250313A: CALET Gamma-Ray Burst Monitor detection
  88. GRB 250312B: Fermi GBM Observation
  89. GRB 250313A: Swift-XRT observations
  90. Konus-Wind detection of GRB 250313A
  91. Konus-Wind detection of GRB 250308A
  92. GRB 250313A: SVOM/GRM observation of a bright long burst
  93. GRB 250313A: AstroSat CZTI detection of a bright long burst
  94. Fermi trigger No 763581136: Global MASTER-Net observations report
  95. GRB 250313A: Fermi-LAT detection
  96. GRB 250313A: Swift ToO observations
  97. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  98. Fermi GRB 250313A: Global MASTER-Net observations report
  99. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  100. GRB 250313A???: BALROG localization (Fermi Trigger / GRB 250313607)

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