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

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