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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"
  1. GRB 250412A: AstroSat CZTI detection
  2. EP250404a: Nanshan 0.43m Telescope optical observatios
  3. Fermi trigger No 766148493: Global MASTER-Net observations report
  4. Fermi trigger No 766173972: Global MASTER-Net observations report
  5. GRB 250411A: DDOTI Optical Observations
  6. Fermi GRB 250411A: Global MASTER-Net observations report
  7. GRB 250411A: Fermi GBM Final Real-time Localization
  8. GRB 250407A: Continued KAIT/Nickel optical observations
  9. GRB 250314A: e-MERLIN observations
  10. GRB 250407A: Mondy and AbAO Optical Observations
  11. EP250227a: Further NOT optical observations
  12. GRB 250320B: cubesat Avion detection
  13. IceCube-250406A: Swift-XRT observations
  14. IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
  15. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A
  16. IPN triangulation of GRB 250407A
  17. EP250407a: Global MASTER-Net observations report
  18. GRB 250407A: LCO detection of a fading optical counterpart
  19. Fermi-LAT gamma-ray observations of IceCube-250406A
  20. EP250407a: Swift-XRT observations
  21. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  22. Konus-Wind detection of GRB 250407A
  23. GRB 250407A: SVOM/GRM observation of a bright long burst
  24. GRB 250407A: EP-WXT afterglow detection
  25. EP250407a: EP-WXT detection of a fast X-ray transient
  26. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  27. GRB 250407A: KAIT Optical Afterglow Candidate
  28. IceCube-250406A: No candidates from the Zwicky Transient Facility
  29. GRB 250407A: Fermi GBM Detection
  30. GRB 250407A: Swift-XRT afterglow detection
  31. Fermi GRB 250407A: Global MASTER-Net observations report
  32. GRB 250407A: Swift ToO observations
  33. GRB 250407A: SRG/ART-XC afterglow detection
  34. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  35. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  36. Konus-Wind detection of GRB 250406B (short/hard)
  37. IPN triangulation of GRB 250406B (short/hard)
  38. GRB 250407A: BALROG localization (Fermi Trigger 765733706 / GRB 250407659)
  39. GRB 250407A: Fermi GBM Final Real-time Localization
  40. IceCube-250406A - IceCube observation of a high-energy neutrino candidate track-like event
  41. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  42. IceCube 250406.951: DDOTI Optical Observations
  43. GRB 250406A: AstroSat CZTI detection
  44. IceCube Alert 250406.95: Global MASTER-Net observations report
  45. Fermi trigger No 765663719: Global MASTER-Net observations report
  46. EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14
  47. Fermi GRB 250406A: Global MASTER-Net observations report
  48. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  49. GRB 250406A: Fermi GBM Final Real-time Localization
  50. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  51. Fermi trigger No 765619921: Global MASTER-Net observations report
  52. Fermi Gamma-ray Burst Monitor trigger 765619921/250406342 is not a GRB
  53. GRB 250404A / EP250404a: RC500 INASAN-Kislovodsk optical upper limit
  54. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  55. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  56. Konus-Wind detection of GRB 250404A / EP250404a
  57. GRB 250404A / EP250404a: Mondy optical observations
  58. EP250404a: refined analysis of the EP-WXT and EP-FXT observations
  59. GRB 250404A / EP250404a: GMG spectroscopic redshift at z ~ 2.627
  60. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  61. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  62. EP250402a: Optical upper limit with PD 1.3m observations
  63. GRB 250404A / EP250404a: NOT optical observations
  64. GRB 250331D: Swift-XRT afterglow detection
  65. GRB 250404B: AstroSat CZTI detection of a short burst
  66. GRB 250403A: AstroSat CZTI detection
  67. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  68. EP250404a: REM optical/NIR observations
  69. EP250404a: Seimei/TriCCS optical counterpart detection
  70. EP250404A: COLIBRÍ/DDRAGO Optical Observations
  71. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  72. EP250404a: LCO optical counterpart detection
  73. Fermi GRB 250404A: Global MASTER-Net observations report
  74. EP250404a: Xinglong decaying optical counterpart
  75. GRB 250403A: Montarrenti Observatory optical detection
  76. GRB 250404A: Fermi GBM Detection
  77. EP250404a: Global MASTER-Net observations report
  78. GRB 250403A: KAIT optical observations
  79. EP250404a: AKO Optical Afterglow Detection
  80. EP250404a: LAST detection of optical counterpart
  81. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  82. EP250404a: Xinglong-2.16m spectroscopic redshift
  83. GRB 250403A: Fermi GBM observations
  84. GRB 250327B: VIRT Optical Upper Limit
  85. EP250404a: Mephisto multi-band optical detection
  86. GRB 250331C Swift-BAT refined analysis
  87. GRB 250331B Swift-BAT refined analysis
  88. GRB 250330A Swift-BAT refined analysis
  89. EP250321A: J band upper limit by SYSU 80cm telescope
  90. EP250404a: BOOTES-4/JGT optical afterglow detection
  91. EP250404a: Nanshan/HMT optical counterpart detection
  92. EP250404a: Einstein Probe detection of an X-ray transient
  93. GRB 250404A: Fermi GBM Final Real-time Localization
  94. GRB 250402A: Mondy optical observations
  95. GRB 250403A: Swift/UVOT Detection
  96. GRB 250402A: Swift/UVOT Upper Limits
  97. EP250402a: Optical upper limit with Kinder observations
  98. GRB 250403A: SVOM/VT optical observation
  99. GRB 250403A: REM NIR afterglow detection
  100. GRB 250403A: LCO optical counterpart detection

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