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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"

3400 results found.

  1. Fermi GRB 250624A: Global MASTER-Net observations report
  2. Fermi GRB 250623A: Global MASTER-Net observations report
  3. Fermi trigger No 772190032: Global MASTER-Net observations report
  4. Fermi GRB 250621A: Global MASTER-Net observations report
  5. GRB 250619B: Fermi GBM Observation
  6. GRB250620C: Fermi GBM Observation
  7. EP250610a: Global MASTER-Net observations report
  8. GRB 250605A: Swift-BAT refined analysis
  9. Fermi trigger No 771072240: Global MASTER-Net observations report
  10. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  11. GRB 250527C: CrAO Optical Upper Limit
  12. EP/WXT 01709177873: GOTO observations confirm stellar variability
  13. Fermi trigger No 770867684: Global MASTER-Net observations report
  14. IPN triangulation of GRB 250529A
  15. Swift GRB250603.05: Global MASTER-Net observations report
  16. GRB 250601A: Swift/XRT candidate afterglow
  17. GRB 250601A: Swift-XRT observations
  18. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  19. GRB 250530A: SVOM/VT optical upper limit
  20. GRB 250527B: Swift-XRT observations
  21. GRB 250527B: Tiled Swift observations
  22. Fermi trigger No 770058372: Global MASTER-Net observations report
  23. GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
  24. EP250526a: Global MASTER-Net observations report
  25. Fermi trigger No 769611916: Global MASTER-Net observations report
  26. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  27. Fermi GRB 250516A: Global MASTER-Net observations report
  28. MAXI GRB250515.65: Global MASTER-Net observations report
  29. Konus-Wind detection of GRB 250512B / EP250512a
  30. Fermi GRB 250512A: Global MASTER-Net observations report
  31. EP250511a: Global MASTER-Net observations report
  32. Fermi GRB 250510C: Global MASTER-Net observations report
  33. EP250508a: REM optical/NIR observations
  34. GRB 250427B : SVOM detection of a burst through offline search
  35. EP#01709175213/IGR J19566+0326: Swift-XRT detection
  36. EP-WXT trigger 01709175213: a new X-ray outburst of LMXB MAXI J1957+032
  37. GRB 250504A: Swift detection of a burst
  38. EP250428b: Global MASTER-Net observations report
  39. GRB 250424A: Swift-BAT refined analysis
  40. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  41. GRB 250424A: BlackGEM optical afterglow detection
  42. IceCube Alert 250421.71: Global MASTER-Net observations report
  43. GRB 250419A: LCO optical observation
  44. GRB 250419A: AKO Optical Afterglow Detection
  45. SVOM/sb25041603 is not a GRB
  46. EP250404a: Nanshan 0.43m Telescope optical observatios
  47. Fermi trigger No 766173972: Global MASTER-Net observations report
  48. Fermi GRB 250407A: Global MASTER-Net observations report
  49. IceCube Alert 250406.95: Global MASTER-Net observations report
  50. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  51. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  52. Fermi GRB 250404A: Global MASTER-Net observations report
  53. GRB 250403A: Montarrenti Observatory optical detection
  54. EP250404a: Global MASTER-Net observations report
  55. GRB 250402A: Fermi GBM Observation
  56. Fermi GRB 250331E: Global MASTER-Net observations report
  57. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  58. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  59. GRB 250331A: MAXI/GSC detection
  60. Fermi GRB 250330B: Global MASTER-Net observations report
  61. IceCube Alert 250330.35: Global MASTER-Net observations report
  62. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  63. GRB 250327B: LCO optical counterpart detection
  64. IPN triangulation of GRB 250322B
  65. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  66. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  67. EP250321a: Kinder optical follow-up observations
  68. Fermi GRB 250320B: Global MASTER-Net observations report
  69. EP250321a: BOOTES-5/JGT optical afterglow detection
  70. EP250321a: TRT optical counterpart detection
  71. Swift GRB 250321A: Global MASTER-Net observations report
  72. GRB 250309B/AT2025dws: further ATCA observations
  73. GRB 250316A: Fermi GBM Final Real-time Localization
  74. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  75. EP250311a/GRB 250311A: Correction to EP-WXT detection time
  76. Fermi GRB 250313A: Global MASTER-Net observations report
  77. EP250311a/GRB 250311A: EP-FXT follow-up observation
  78. Fermi GRB 250312B: Global MASTER-Net observations report
  79. GRB 250312B: Fermi GBM Final Localization
  80. GRB 241228A: VIRT Optical Upper Limit
  81. GRB 250311A: Swift-XRT observations
  82. GRB 250311A/EP250311a: TRT optical upper limit
  83. GRB 250311A: Tiled Swift observations
  84. EP250311a/GRB 250311A: EP-WXT detection
  85. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  86. IceCube Alert 250309.32: Global MASTER-Net observations report
  87. EP250308a: Global MASTER-Net observations report
  88. EP250308a: Einstein Probe detection of an X-ray transient
  89. GRB 250307A: Fermi GBM Final Real-time Localization
  90. GRB 250306A: Swift-BAT refined analysis
  91. GRB 250305A: AstroSat CZTI detection
  92. Fermi trigger No 762963055: Global MASTER-Net observations report
  93. GRB 250305A: Fermi GBM Final Real-time Localization
  94. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  95. EP250302a: Montarrenti Observatory optical detection
  96. Fermi GRB 250302A: Global MASTER-Net observations report
  97. EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
  98. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  99. EP250226a / GRB 250226A: TRT optical counterpart observation
  100. GRB 250226A: Fermi GBM Final Real-time Localization

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