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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"

45415 results found.

  1. EP250416a: Einstein Probe detection of an X-ray transient
  2. IceCube-250416A - IceCube observation of a high-energy neutrino candidate track-like event
  3. IceCube-250416A: Global MASTER-Net observations report
  4. Fermi Gamma-ray Burst Monitor trigger 766511207/250416657 is not a GRB
  5. GRB 250416B: Fermi GBM Final Real-time Localization
  6. GRB 250416A: Fermi GBM Final Real-time Localization
  7. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  8. SVOM/sb25041603: SVOM detection of an X-ray transient
  9. Fermi Gamma-ray Burst Monitor trigger 766474855/250416237 is not a GRB
  10. IceCube 250414.324: DDOTI Optical Observations
  11. GRB 250413A: AstroSat CZTI detection
  12. EP250304a: ATCA radio observations
  13. GRB 250412A: AstroSat CZTI detection
  14. EP250404a: Nanshan 0.43m Telescope optical observatios
  15. Fermi trigger No 766148493: Global MASTER-Net observations report
  16. Fermi trigger No 766173972: Global MASTER-Net observations report
  17. GRB 250411A: DDOTI Optical Observations
  18. Fermi GRB 250411A: Global MASTER-Net observations report
  19. GRB 250411A: Fermi GBM Final Real-time Localization
  20. GRB 250407A: Continued KAIT/Nickel optical observations
  21. GRB 250314A: e-MERLIN observations
  22. GRB 250407A: Mondy and AbAO Optical Observations
  23. EP250227a: Further NOT optical observations
  24. GRB 250320B: cubesat Avion detection
  25. IceCube-250406A: Swift-XRT observations
  26. IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
  27. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A
  28. IPN triangulation of GRB 250407A
  29. EP250407a: Global MASTER-Net observations report
  30. GRB 250407A: LCO detection of a fading optical counterpart
  31. Fermi-LAT gamma-ray observations of IceCube-250406A
  32. EP250407a: Swift-XRT observations
  33. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  34. Konus-Wind detection of GRB 250407A
  35. GRB 250407A: SVOM/GRM observation of a bright long burst
  36. GRB 250407A: EP-WXT afterglow detection
  37. EP250407a: EP-WXT detection of a fast X-ray transient
  38. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  39. GRB 250407A: KAIT Optical Afterglow Candidate
  40. IceCube-250406A: No candidates from the Zwicky Transient Facility
  41. GRB 250407A: Fermi GBM Detection
  42. GRB 250407A: Swift-XRT afterglow detection
  43. Fermi GRB 250407A: Global MASTER-Net observations report
  44. GRB 250407A: Swift ToO observations
  45. GRB 250407A: SRG/ART-XC afterglow detection
  46. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  47. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  48. Konus-Wind detection of GRB 250406B (short/hard)
  49. IPN triangulation of GRB 250406B (short/hard)
  50. GRB 250407A: BALROG localization (Fermi Trigger 765733706 / GRB 250407659)
  51. GRB 250407A: Fermi GBM Final Real-time Localization
  52. IceCube-250406A - IceCube observation of a high-energy neutrino candidate track-like event
  53. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  54. IceCube 250406.951: DDOTI Optical Observations
  55. GRB 250406A: AstroSat CZTI detection
  56. IceCube Alert 250406.95: Global MASTER-Net observations report
  57. Fermi trigger No 765663719: Global MASTER-Net observations report
  58. EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14
  59. Fermi GRB 250406A: Global MASTER-Net observations report
  60. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  61. GRB 250406A: Fermi GBM Final Real-time Localization
  62. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  63. Fermi trigger No 765619921: Global MASTER-Net observations report
  64. Fermi Gamma-ray Burst Monitor trigger 765619921/250406342 is not a GRB
  65. GRB 250404A / EP250404a: RC500 INASAN-Kislovodsk optical upper limit
  66. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  67. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  68. Konus-Wind detection of GRB 250404A / EP250404a
  69. GRB 250404A / EP250404a: Mondy optical observations
  70. EP250404a: refined analysis of the EP-WXT and EP-FXT observations
  71. GRB 250404A / EP250404a: GMG spectroscopic redshift at z ~ 2.627
  72. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  73. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  74. EP250402a: Optical upper limit with PD 1.3m observations
  75. GRB 250404A / EP250404a: NOT optical observations
  76. GRB 250331D: Swift-XRT afterglow detection
  77. GRB 250404B: AstroSat CZTI detection of a short burst
  78. GRB 250403A: AstroSat CZTI detection
  79. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  80. EP250404a: REM optical/NIR observations
  81. EP250404a: Seimei/TriCCS optical counterpart detection
  82. EP250404A: COLIBRÍ/DDRAGO Optical Observations
  83. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  84. EP250404a: LCO optical counterpart detection
  85. Fermi GRB 250404A: Global MASTER-Net observations report
  86. EP250404a: Xinglong decaying optical counterpart
  87. GRB 250403A: Montarrenti Observatory optical detection
  88. GRB 250404A: Fermi GBM Detection
  89. EP250404a: Global MASTER-Net observations report
  90. GRB 250403A: KAIT optical observations
  91. EP250404a: AKO Optical Afterglow Detection
  92. EP250404a: LAST detection of optical counterpart
  93. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  94. EP250404a: Xinglong-2.16m spectroscopic redshift
  95. GRB 250403A: Fermi GBM observations
  96. GRB 250327B: VIRT Optical Upper Limit
  97. EP250404a: Mephisto multi-band optical detection
  98. GRB 250331C Swift-BAT refined analysis
  99. GRB 250331B Swift-BAT refined analysis
  100. GRB 250330A Swift-BAT refined analysis

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