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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"

3039 results found.

  1. GRB 250821A: KAIT optical upper limit
  2. LIGO/Virgo/KAGRA S250818k : Tautenburg observations, upper limits
  3. Fermi trigger No 776849714: Global MASTER-Net observations report
  4. GRB 250814A: Further GRAWITA TNG NIR observations
  5. Fermi trigger No 776818276: Global MASTER-Net observations report
  6. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  7. IceCube Alert 250813.14: Global MASTER-Net observations report
  8. IceCube-Cascade 250809A: Upper limits from a search for additional neutrino events in IceCube
  9. EP250807a: COLIBRÍ optical upper limit
  10. EP250806a: Global MASTER-Net observations report
  11. GRB 250805A: Swift-BAT refined analysis
  12. GRB 250804C: AstroSat CZTI detection of a long burst
  13. GRB 250805A: Swift detection of a burst
  14. EP250711a: CrAO and Assy optical observations
  15. EP250730a: Global MASTER-Net observations report
  16. GRB 250727A: EP-FXT follow-up observation
  17. GRB 250725A: Swift-BAT refined analysis
  18. GRB 250720B: Fermi GBM Final Localization Correction
  19. Swift GRB250718.01: Global MASTER-Net observations report
  20. Fermi GRB 250716A: Global MASTER-Net observations report
  21. GRB 250706B/C: 7DT Follow-up Observations
  22. EP250711a: COLIBRÍ continuous optical observations
  23. Fermi GRB 250711A: Global MASTER-Net observations report
  24. GRB 250704B / EP250704a: VLA radio detection
  25. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  26. GRB 250702F: Leavitt Observatory optical observations
  27. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  28. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  29. GRB 250702F: Swift detection of a burst with an optical counterpart
  30. GRB 250628A: Swift detection of a burst
  31. Fermi Gamma-ray Burst Monitor trigger 772732642/250627665 is not a GRB
  32. GRB 250625A: Fermi GBM Final Real-time Localization
  33. Fermi GRB 250624A: Global MASTER-Net observations report
  34. Fermi GRB 250623A: Global MASTER-Net observations report
  35. Fermi trigger No 772190032: Global MASTER-Net observations report
  36. Fermi GRB 250621A: Global MASTER-Net observations report
  37. GRB 250619B: Fermi GBM Observation
  38. GRB250620C: Fermi GBM Observation
  39. EP250610a: Global MASTER-Net observations report
  40. GRB 250605A: Swift-BAT refined analysis
  41. Fermi trigger No 771072240: Global MASTER-Net observations report
  42. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  43. GRB 250527C: CrAO Optical Upper Limit
  44. EP/WXT 01709177873: GOTO observations confirm stellar variability
  45. Fermi trigger No 770867684: Global MASTER-Net observations report
  46. IPN triangulation of GRB 250529A
  47. Swift GRB250603.05: Global MASTER-Net observations report
  48. GRB 250601A: Swift/XRT candidate afterglow
  49. GRB 250601A: Swift-XRT observations
  50. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  51. GRB 250530A: SVOM/VT optical upper limit
  52. Fermi trigger No 770058372: Global MASTER-Net observations report
  53. EP250526a: Global MASTER-Net observations report
  54. Fermi trigger No 769611916: Global MASTER-Net observations report
  55. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  56. Fermi GRB 250516A: Global MASTER-Net observations report
  57. Konus-Wind detection of GRB 250512B / EP250512a
  58. Fermi GRB 250512A: Global MASTER-Net observations report
  59. EP250511a: Global MASTER-Net observations report
  60. Fermi GRB 250510C: Global MASTER-Net observations report
  61. EP250508a: REM optical/NIR observations
  62. GRB 250427B : SVOM detection of a burst through offline search
  63. GRB 250504A: Swift detection of a burst
  64. EP250428b: Global MASTER-Net observations report
  65. GRB 250424A: Swift-BAT refined analysis
  66. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  67. GRB 250424A: BlackGEM optical afterglow detection
  68. IceCube Alert 250421.71: Global MASTER-Net observations report
  69. GRB 250419A: LCO optical observation
  70. GRB 250419A: AKO Optical Afterglow Detection
  71. SVOM/sb25041603 is not a GRB
  72. EP250404a: Nanshan 0.43m Telescope optical observatios
  73. Fermi trigger No 766173972: Global MASTER-Net observations report
  74. Fermi GRB 250407A: Global MASTER-Net observations report
  75. IceCube Alert 250406.95: Global MASTER-Net observations report
  76. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  77. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  78. Fermi GRB 250404A: Global MASTER-Net observations report
  79. GRB 250403A: Montarrenti Observatory optical detection
  80. EP250404a: Global MASTER-Net observations report
  81. GRB 250402A: Fermi GBM Observation
  82. Fermi GRB 250331E: Global MASTER-Net observations report
  83. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  84. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  85. GRB 250331A: MAXI/GSC detection
  86. Fermi GRB 250330B: Global MASTER-Net observations report
  87. IceCube Alert 250330.35: Global MASTER-Net observations report
  88. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  89. GRB 250327B: LCO optical counterpart detection
  90. IPN triangulation of GRB 250322B
  91. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  92. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  93. EP250321a: Kinder optical follow-up observations
  94. Fermi GRB 250320B: Global MASTER-Net observations report
  95. EP250321a: BOOTES-5/JGT optical afterglow detection
  96. EP250321a: TRT optical counterpart detection
  97. Swift GRB 250321A: Global MASTER-Net observations report
  98. GRB 250309B/AT2025dws: further ATCA observations
  99. GRB 250316A: Fermi GBM Final Real-time Localization
  100. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits

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