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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 250421A: Fermi GBM Final Real-time Localization
  2. GRB 250419A: Liverpool Telescope observations
  3. GRB 250419A: LCO optical observation
  4. GRB 250419A: JinShan optical observations
  5. GRB 250419A: SVOM/VT optical continuous observations
  6. GRB 250419A: SVOM/C-GFT optical observations
  7. GRB 250419A: Swift/UVOT Follow up
  8. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  9. GRB 250419A: LCO optical afterglow multi-band observations
  10. GRB 250419A: Mondy and AbAO Optical Observations
  11. GRB 250419A: Liverpool Telescope observations
  12. GRB 250419A: AKO Optical Afterglow Detection
  13. GRB 250419A: MASTER optical afterglow observation
  14. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  15. GRB 250407A: rest-frame energetics from Konus-Wind observation
  16. GRB 250419A: Swift-XRT localisation
  17. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  18. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  19. GRB 250419A: Swift-XRT refined Analysis
  20. GRB 250419A: GOTO optical counterpart detection
  21. GRB 250419A: KAIT optical afterglow observations
  22. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  23. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  24. GRB 250419A: SVOM detection of a soft burst
  25. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  26. EP250416a: Swift/XRT counterpart fading
  27. EP250416a: refined EP-WXT and EP-FXT analysis
  28. Konus-Wind detection of GRB 250403A
  29. EP20250416a: Swift/XRT counterpart detection
  30. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  31. IceCube-250416A: DDOTI Optical Observations
  32. EP250416a: Gemini South-GMOS optical counterpart
  33. EP250225a: SVOM/VT optical brightening
  34. SVOM/sb25041603 is not a GRB
  35. EP250416a: GSP optical upper limit
  36. EP250416a: Global MASTER-Net observations report
  37. Fermi Gamma-ray Burst Monitor trigger 766505186/250416588 (GRB 250416A) is not a GRB
  38. EP250416a: Einstein Probe detection of an X-ray transient
  39. IceCube-250416A - IceCube observation of a high-energy neutrino candidate track-like event
  40. IceCube-250416A: Global MASTER-Net observations report
  41. Fermi Gamma-ray Burst Monitor trigger 766511207/250416657 is not a GRB
  42. GRB 250416B: Fermi GBM Final Real-time Localization
  43. GRB 250416A: Fermi GBM Final Real-time Localization
  44. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  45. SVOM/sb25041603: SVOM detection of an X-ray transient
  46. Fermi Gamma-ray Burst Monitor trigger 766474855/250416237 is not a GRB
  47. IceCube 250414.324: DDOTI Optical Observations
  48. GRB 250413A: AstroSat CZTI detection
  49. EP250304a: ATCA radio observations
  50. GRB 250412A: AstroSat CZTI detection
  51. EP250404a: Nanshan 0.43m Telescope optical observatios
  52. Fermi trigger No 766148493: Global MASTER-Net observations report
  53. Fermi trigger No 766173972: Global MASTER-Net observations report
  54. GRB 250411A: DDOTI Optical Observations
  55. Fermi GRB 250411A: Global MASTER-Net observations report
  56. GRB 250411A: Fermi GBM Final Real-time Localization
  57. GRB 250407A: Continued KAIT/Nickel optical observations
  58. GRB 250314A: e-MERLIN observations
  59. GRB 250407A: Mondy and AbAO Optical Observations
  60. EP250227a: Further NOT optical observations
  61. GRB 250320B: cubesat Avion detection
  62. IceCube-250406A: Swift-XRT observations
  63. IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
  64. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A
  65. IPN triangulation of GRB 250407A
  66. EP250407a: Global MASTER-Net observations report
  67. GRB 250407A: LCO detection of a fading optical counterpart
  68. Fermi-LAT gamma-ray observations of IceCube-250406A
  69. EP250407a: Swift-XRT observations
  70. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  71. Konus-Wind detection of GRB 250407A
  72. GRB 250407A: SVOM/GRM observation of a bright long burst
  73. GRB 250407A: EP-WXT afterglow detection
  74. EP250407a: EP-WXT detection of a fast X-ray transient
  75. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  76. GRB 250407A: KAIT Optical Afterglow Candidate
  77. IceCube-250406A: No candidates from the Zwicky Transient Facility
  78. GRB 250407A: Fermi GBM Detection
  79. GRB 250407A: Swift-XRT afterglow detection
  80. Fermi GRB 250407A: Global MASTER-Net observations report
  81. GRB 250407A: Swift ToO observations
  82. GRB 250407A: SRG/ART-XC afterglow detection
  83. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  84. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  85. Konus-Wind detection of GRB 250406B (short/hard)
  86. IPN triangulation of GRB 250406B (short/hard)
  87. GRB 250407A: BALROG localization (Fermi Trigger 765733706 / GRB 250407659)
  88. GRB 250407A: Fermi GBM Final Real-time Localization
  89. IceCube-250406A - IceCube observation of a high-energy neutrino candidate track-like event
  90. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  91. IceCube 250406.951: DDOTI Optical Observations
  92. GRB 250406A: AstroSat CZTI detection
  93. IceCube Alert 250406.95: Global MASTER-Net observations report
  94. Fermi trigger No 765663719: Global MASTER-Net observations report
  95. EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14
  96. Fermi GRB 250406A: Global MASTER-Net observations report
  97. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  98. GRB 250406A: Fermi GBM Final Real-time Localization
  99. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  100. Fermi trigger No 765619921: Global MASTER-Net observations report

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