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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"

4878 results found.

  1. Fermi GRB 250522B: Global MASTER-Net observations report
  2. GRB 250522A: Fermi GBM Final Real-time Localization
  3. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  4. GRB 250520A: Swift-XRT refined Analysis
  5. Fermi GRB 250516A: Global MASTER-Net observations report
  6. GRB 250516A: Swift-XRT refined Analysis
  7. Fermi GRB 250512A: Global MASTER-Net observations report
  8. EP250512a: Global MASTER-Net observations report
  9. Fermi GRB 250510C: Global MASTER-Net observations report
  10. GRB 250510C: Fermi GBM Final Real-time Localization
  11. IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
  12. GRB 250509A: Swift-XRT refined Analysis
  13. EP250508a: Liverpool Telescope optical upper limits
  14. GRB 250502A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  15. EP250508a: Global MASTER-Net observations report
  16. GRB 250504A: Swift-XRT refined Analysis
  17. Fermi GRB 250502B: Global MASTER-Net observations report
  18. GRB 250430A: SVOM/VT optical observations
  19. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  20. Fermi trigger No 767623859: Global MASTER-Net observations report
  21. EP250428b: SAO RAS optical upper limit
  22. GRB 250424A: LCO optical observation
  23. EP250427a: TRT optical counterpart detection
  24. GRB 250424A: WINTER J-band detection
  25. GRB 250424A: EIRSAT-1 GMOD Detection
  26. GRB 250424A: SVOM/VT optical observation
  27. GRB 250424A: Swift-XRT refined Analysis
  28. GRB 250424A: AstroSat CZTI detection of a bright long burst
  29. GRB 250424A: BlackGEM optical afterglow detection
  30. GRB 250424A: DDOTI Afterglow Detection
  31. GRB 250424A: REM optical/NIR afterglow detection
  32. Swift GRB 250424A: Global MASTER-Net observations report
  33. Swift GRB 250424A: Global MASTER-Net OT detection
  34. SVOM/sb25042207: BOOTES-2 early optical upper limit
  35. EP250421a: Swift/XRT counterpart detection
  36. Fermi GRB 250421A: Global MASTER-Net observations report
  37. IceCube Alert 250421.71: Global MASTER-Net observations report
  38. EP250421a: JinShan likely optical counterpart
  39. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  40. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  41. IceCube-250416A: DDOTI Optical Observations
  42. EP250404a: Nanshan 0.43m Telescope optical observatios
  43. Fermi trigger No 766148493: Global MASTER-Net observations report
  44. Fermi trigger No 766173972: Global MASTER-Net observations report
  45. Fermi GRB 250411A: Global MASTER-Net observations report
  46. IPN triangulation of GRB 250407A
  47. Fermi GRB 250407A: Global MASTER-Net observations report
  48. IceCube 250406.951: DDOTI Optical Observations
  49. IceCube Alert 250406.95: Global MASTER-Net observations report
  50. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  51. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  52. GRB 250404A / EP250404a: GMG spectroscopic redshift at z ~ 2.627
  53. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  54. Fermi GRB 250404A: Global MASTER-Net observations report
  55. EP250404a: Xinglong decaying optical counterpart
  56. GRB 250403A: Montarrenti Observatory optical detection
  57. EP250404a: Global MASTER-Net observations report
  58. EP250404a: Nanshan/HMT optical counterpart detection
  59. GRB 250403A: Swift/UVOT Detection
  60. EP250402a: Optical upper limit with Kinder observations
  61. GRB 250403A: Swift-XRT observations
  62. GRB 250403A: GOTO optical counterpart follow-up observations
  63. GRB 250403A: GMG Optical Observation
  64. GRB 250331C: Swift-XRT refined Analysis
  65. GRB 250331B: Swift-XRT refined Analysis
  66. GRB 250331B: Swift-XRT refined Analysis
  67. Fermi GRB 250331E: Global MASTER-Net observations report
  68. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  69. GRB 250331B: Swift detection of a burst
  70. GRB 250331A: MAXI/GSC detection
  71. GRB 250330A: Swift-XRT afterglow detection
  72. IceCube Alert 250330.35: Global MASTER-Net observations report
  73. GRB 250327B: CrAO and SAO RAS Optical Observations
  74. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  75. GRB 250327A: Swift-XRT refined Analysis
  76. GRB 250327B: GOTO optical counterpart detection
  77. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  78. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  79. GRB 250322A: Swift-XRT refined Analysis
  80. GRB 250322A: AstroSat CZTI detection of a short burst
  81. FRB 250316A: DDOTI Continued Optical Observations
  82. EP250321a: Liverpool Telescope optical follow-up
  83. GRB 250312A: GECAM-A detection
  84. GRB 250321A: Swift-BAT refined analysis
  85. GRB 250321A: Swift-XRT refined Analysis
  86. GRB 250317B: NOT optical observations suggest an optical plateau phase
  87. Fermi GRB 250316A: Global MASTER-Net observations report
  88. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  89. Fermi GRB 250313A: Global MASTER-Net observations report
  90. GRB 250312A: Swift-XRT refined Analysis
  91. GRB 250312A: Swift detection of a burst
  92. GRB 250309B: 1.3m DFOT Optical observations
  93. IPN triangulation of GRB 250308A (short)
  94. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  95. GRB 250309B: Swift-XRT refined Analysis
  96. IceCube Alert 250309.32: Global MASTER-Net observations report
  97. Fermi GRB 250307A: Global MASTER-Net observations report
  98. Fermi trigger No 762963055: Global MASTER-Net observations report
  99. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  100. Konus-Wind detection of GRB 250222A

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