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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"

3724 results found.

  1. GRB 250721A: Fermi GBM Observation
  2. GRB 250721A: Swift-XRT observations
  3. GRB 250721A: Tiled Swift observations
  4. GRB 250721A: MAXI/GSC detection
  5. GRB 250720B: Fermi GBM Final Localization Correction
  6. Swift GRB250718.01: Global MASTER-Net observations report
  7. Fermi GRB 250716A: Global MASTER-Net observations report
  8. GRB 250706B/C: 7DT Follow-up Observations
  9. EP250711a: COLIBRÍ continuous optical observations
  10. Fermi GRB 250711A: Global MASTER-Net observations report
  11. GRB 250704B / EP250704a: VLA radio detection
  12. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  13. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  14. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  15. GRB 250702F: Leavitt Observatory optical observations
  16. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  17. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  18. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  19. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  20. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  21. GRB 250702F: Swift detection of a burst with an optical counterpart
  22. GRB 250628A: Swift detection of a burst
  23. Fermi Gamma-ray Burst Monitor trigger 772732642/250627665 is not a GRB
  24. GRB 250625A: Fermi GBM Final Real-time Localization
  25. Fermi GRB 250624A: Global MASTER-Net observations report
  26. Fermi GRB 250623A: Global MASTER-Net observations report
  27. Fermi trigger No 772190032: Global MASTER-Net observations report
  28. Fermi GRB 250621A: Global MASTER-Net observations report
  29. GRB 250619B: Fermi GBM Observation
  30. GRB250620C: Fermi GBM Observation
  31. EP250610a: Global MASTER-Net observations report
  32. GRB 250605A: Swift-BAT refined analysis
  33. Fermi trigger No 771072240: Global MASTER-Net observations report
  34. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  35. GRB 250527C: CrAO Optical Upper Limit
  36. EP/WXT 01709177873: GOTO observations confirm stellar variability
  37. Fermi trigger No 770867684: Global MASTER-Net observations report
  38. IPN triangulation of GRB 250529A
  39. Swift GRB250603.05: Global MASTER-Net observations report
  40. GRB 250601A: Swift/XRT candidate afterglow
  41. GRB 250601A: Swift-XRT observations
  42. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  43. GRB 250530A: SVOM/VT optical upper limit
  44. GRB 250527B: Swift-XRT observations
  45. GRB 250527B: Tiled Swift observations
  46. Fermi trigger No 770058372: Global MASTER-Net observations report
  47. GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
  48. EP250526a: Global MASTER-Net observations report
  49. Fermi trigger No 769611916: Global MASTER-Net observations report
  50. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  51. Fermi GRB 250516A: Global MASTER-Net observations report
  52. MAXI GRB250515.65: Global MASTER-Net observations report
  53. Konus-Wind detection of GRB 250512B / EP250512a
  54. Fermi GRB 250512A: Global MASTER-Net observations report
  55. EP250511a: Global MASTER-Net observations report
  56. Fermi GRB 250510C: Global MASTER-Net observations report
  57. EP250508a: REM optical/NIR observations
  58. GRB 250427B : SVOM detection of a burst through offline search
  59. EP#01709175213/IGR J19566+0326: Swift-XRT detection
  60. EP-WXT trigger 01709175213: a new X-ray outburst of LMXB MAXI J1957+032
  61. GRB 250504A: Swift detection of a burst
  62. EP250428b: Global MASTER-Net observations report
  63. GRB 250424A: Swift-BAT refined analysis
  64. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  65. GRB 250424A: BlackGEM optical afterglow detection
  66. IceCube Alert 250421.71: Global MASTER-Net observations report
  67. GRB 250419A: LCO optical observation
  68. GRB 250419A: AKO Optical Afterglow Detection
  69. SVOM/sb25041603 is not a GRB
  70. EP250404a: Nanshan 0.43m Telescope optical observatios
  71. Fermi trigger No 766173972: Global MASTER-Net observations report
  72. Fermi GRB 250407A: Global MASTER-Net observations report
  73. IceCube Alert 250406.95: Global MASTER-Net observations report
  74. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  75. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  76. Fermi GRB 250404A: Global MASTER-Net observations report
  77. GRB 250403A: Montarrenti Observatory optical detection
  78. EP250404a: Global MASTER-Net observations report
  79. GRB 250402A: Fermi GBM Observation
  80. Fermi GRB 250331E: Global MASTER-Net observations report
  81. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  82. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  83. GRB 250331A: MAXI/GSC detection
  84. Fermi GRB 250330B: Global MASTER-Net observations report
  85. IceCube Alert 250330.35: Global MASTER-Net observations report
  86. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  87. GRB 250327B: LCO optical counterpart detection
  88. IPN triangulation of GRB 250322B
  89. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  90. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  91. EP250321a: Kinder optical follow-up observations
  92. Fermi GRB 250320B: Global MASTER-Net observations report
  93. EP250321a: BOOTES-5/JGT optical afterglow detection
  94. EP250321a: TRT optical counterpart detection
  95. Swift GRB 250321A: Global MASTER-Net observations report
  96. GRB 250309B/AT2025dws: further ATCA observations
  97. GRB 250316A: Fermi GBM Final Real-time Localization
  98. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  99. EP250311a/GRB 250311A: Correction to EP-WXT detection time
  100. Fermi GRB 250313A: Global MASTER-Net observations report

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