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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 250419A: KAIT optical afterglow observations
  2. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  3. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  4. GRB 250419A: SVOM detection of a soft burst
  5. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  6. EP250416a: Swift/XRT counterpart fading
  7. EP250416a: refined EP-WXT and EP-FXT analysis
  8. Konus-Wind detection of GRB 250403A
  9. EP20250416a: Swift/XRT counterpart detection
  10. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  11. IceCube-250416A: DDOTI Optical Observations
  12. EP250416a: Gemini South-GMOS optical counterpart
  13. EP250225a: SVOM/VT optical brightening
  14. SVOM/sb25041603 is not a GRB
  15. EP250416a: GSP optical upper limit
  16. EP250416a: Global MASTER-Net observations report
  17. Fermi Gamma-ray Burst Monitor trigger 766505186/250416588 (GRB 250416A) is not a GRB
  18. EP250416a: Einstein Probe detection of an X-ray transient
  19. IceCube-250416A - IceCube observation of a high-energy neutrino candidate track-like event
  20. IceCube-250416A: Global MASTER-Net observations report
  21. Fermi Gamma-ray Burst Monitor trigger 766511207/250416657 is not a GRB
  22. GRB 250416B: Fermi GBM Final Real-time Localization
  23. GRB 250416A: Fermi GBM Final Real-time Localization
  24. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  25. SVOM/sb25041603: SVOM detection of an X-ray transient
  26. Fermi Gamma-ray Burst Monitor trigger 766474855/250416237 is not a GRB
  27. IceCube 250414.324: DDOTI Optical Observations
  28. GRB 250413A: AstroSat CZTI detection
  29. EP250304a: ATCA radio observations
  30. GRB 250412A: AstroSat CZTI detection
  31. EP250404a: Nanshan 0.43m Telescope optical observatios
  32. Fermi trigger No 766148493: Global MASTER-Net observations report
  33. Fermi trigger No 766173972: Global MASTER-Net observations report
  34. GRB 250411A: DDOTI Optical Observations
  35. Fermi GRB 250411A: Global MASTER-Net observations report
  36. GRB 250411A: Fermi GBM Final Real-time Localization
  37. GRB 250407A: Continued KAIT/Nickel optical observations
  38. GRB 250314A: e-MERLIN observations
  39. GRB 250407A: Mondy and AbAO Optical Observations
  40. EP250227a: Further NOT optical observations
  41. GRB 250320B: cubesat Avion detection
  42. IceCube-250406A: Swift-XRT observations
  43. IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
  44. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A
  45. IPN triangulation of GRB 250407A
  46. EP250407a: Global MASTER-Net observations report
  47. GRB 250407A: LCO detection of a fading optical counterpart
  48. Fermi-LAT gamma-ray observations of IceCube-250406A
  49. EP250407a: Swift-XRT observations
  50. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  51. Konus-Wind detection of GRB 250407A
  52. GRB 250407A: SVOM/GRM observation of a bright long burst
  53. GRB 250407A: EP-WXT afterglow detection
  54. EP250407a: EP-WXT detection of a fast X-ray transient
  55. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  56. GRB 250407A: KAIT Optical Afterglow Candidate
  57. IceCube-250406A: No candidates from the Zwicky Transient Facility
  58. GRB 250407A: Fermi GBM Detection
  59. GRB 250407A: Swift-XRT afterglow detection
  60. Fermi GRB 250407A: Global MASTER-Net observations report
  61. GRB 250407A: Swift ToO observations
  62. GRB 250407A: SRG/ART-XC afterglow detection
  63. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  64. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  65. Konus-Wind detection of GRB 250406B (short/hard)
  66. IPN triangulation of GRB 250406B (short/hard)
  67. GRB 250407A: BALROG localization (Fermi Trigger 765733706 / GRB 250407659)
  68. GRB 250407A: Fermi GBM Final Real-time Localization
  69. IceCube-250406A - IceCube observation of a high-energy neutrino candidate track-like event
  70. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  71. IceCube 250406.951: DDOTI Optical Observations
  72. GRB 250406A: AstroSat CZTI detection
  73. IceCube Alert 250406.95: Global MASTER-Net observations report
  74. Fermi trigger No 765663719: Global MASTER-Net observations report
  75. EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14
  76. Fermi GRB 250406A: Global MASTER-Net observations report
  77. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  78. GRB 250406A: Fermi GBM Final Real-time Localization
  79. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  80. Fermi trigger No 765619921: Global MASTER-Net observations report
  81. Fermi Gamma-ray Burst Monitor trigger 765619921/250406342 is not a GRB
  82. GRB 250404A / EP250404a: RC500 INASAN-Kislovodsk optical upper limit
  83. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  84. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  85. Konus-Wind detection of GRB 250404A / EP250404a
  86. GRB 250404A / EP250404a: Mondy optical observations
  87. EP250404a: refined analysis of the EP-WXT and EP-FXT observations
  88. GRB 250404A / EP250404a: GMG spectroscopic redshift at z ~ 2.627
  89. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  90. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  91. EP250402a: Optical upper limit with PD 1.3m observations
  92. GRB 250404A / EP250404a: NOT optical observations
  93. GRB 250331D: Swift-XRT afterglow detection
  94. GRB 250404B: AstroSat CZTI detection of a short burst
  95. GRB 250403A: AstroSat CZTI detection
  96. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  97. EP250404a: REM optical/NIR observations
  98. EP250404a: Seimei/TriCCS optical counterpart detection
  99. EP250404A: COLIBRÍ/DDRAGO Optical Observations
  100. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection

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