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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"

24373 results found.

  1. GRB 250430A : MITSuME Akeno optical upper limits
  2. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  3. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  4. IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
  5. IceCube-250426A: Upper limits from a search for additional neutrino events in IceCube
  6. Swift GRB250430.73: Global MASTER-Net observations report
  7. EP250428b: FTW optical and NIR observations
  8. SVOM/sb25043004: SVOM detection of a X-ray transient
  9. Fermi trigger No 767623859: Global MASTER-Net observations report
  10. EP250428b: refined analysis of the EP-FXT follow-up observation
  11. EP250428b: SVOM/VT upper limit
  12. IceCube-250429A - IceCube observation of a high-energy neutrino candidate track-like event
  13. EP250428b: Global MASTER-Net observations report
  14. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  15. EP250427a: EP-FXT follow-up observations
  16. EP250427a: LT optical counterpart detection
  17. EP250427a / GRB 250427A: LCO optical counterpart detection
  18. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  19. EP250427A/GRB250427A: Keck/LRIS redshift
  20. EP250427a: REM optical/NIR afterglow detection
  21. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  22. EP250427a: Global MASTER-Net observations report
  23. EP250427a: Einstein Probe detection of a fast X-ray transient
  24. IceCube Alert 250426.74: Global MASTER-Net observations report
  25. GRB 250424A: Swift-BAT refined analysis
  26. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event
  27. GRB 250424A: SVOM/GRM observation of a long burst
  28. GRB 250424A: EIRSAT-1 GMOD Detection
  29. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  30. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  31. GRB 250424A: SVOM/VT optical observation
  32. Konus-Wind detection of GRB 250424A
  33. Fermi-LAT gamma-ray observations of IceCube-250421A
  34. GRB 250419A: Liverpool Telescope optical upper limit
  35. GRB 250407A: GRBAlpha detection
  36. GRB 250404A / EP250404a: GRBAlpha detection
  37. GRB 250330B: GRBAlpha detection
  38. GRB 250419A: SVOM/ECLAIRs refined analysis
  39. GRB 250424A: BlackGEM optical afterglow detection
  40. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  41. GRB 250424A: REM optical/NIR afterglow detection
  42. Swift GRB 250424A: Global MASTER-Net observations report
  43. Swift GRB 250424A: Global MASTER-Net OT detection
  44. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  45. EP250421a: Nickel optical upper limit
  46. EP250421a: Upper limits from Fermi-GBM Observations
  47. SVOM/sb25042207: BOOTES-2 early optical upper limit
  48. SVOM/sb25042207: GOTO optical upper limits
  49. SVOM/sb25042207: SVOM detection of an X-ray transient
  50. GRB 250419A: Mephisto Multi-band Optical Detection
  51. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  52. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  53. GRB 250419A: Optical Observations via Virtual Telescope Project
  54. EP250421a: REM optical upper limit
  55. Fermi GRB 250421A: Global MASTER-Net observations report
  56. EP250421a: Global MASTER-Net observations report
  57. EP250421a: Mephisto optical counterpart confirmation
  58. IceCube Alert 250421.71: Global MASTER-Net observations report
  59. IceCube-250421A - IceCube observation of a high-energy neutrino candidate track-like event
  60. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  61. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  62. GRB 250421A: Fermi GBM Final Real-time Localization
  63. GRB 250419A: SVOM/VT optical continuous observations
  64. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  65. GRB 250419A: LCO optical afterglow multi-band observations
  66. GRB 250419A: MASTER optical afterglow observation
  67. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  68. GRB 250407A: rest-frame energetics from Konus-Wind observation
  69. GRB 250419A: GOTO optical counterpart detection
  70. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  71. GRB 250419A: SVOM detection of a soft burst
  72. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  73. EP250416a: refined EP-WXT and EP-FXT analysis
  74. Konus-Wind detection of GRB 250403A
  75. EP250416a: Gemini South-GMOS optical counterpart
  76. EP250225a: SVOM/VT optical brightening
  77. SVOM/sb25041603 is not a GRB
  78. EP250416a: Global MASTER-Net observations report
  79. IceCube-250416A - IceCube observation of a high-energy neutrino candidate track-like event
  80. IceCube-250416A: Global MASTER-Net observations report
  81. GRB 250416B: Fermi GBM Final Real-time Localization
  82. GRB 250416A: Fermi GBM Final Real-time Localization
  83. SVOM/sb25041603: SVOM detection of an X-ray transient
  84. GRB 250413A: AstroSat CZTI detection
  85. EP250404a: Nanshan 0.43m Telescope optical observatios
  86. Fermi trigger No 766148493: Global MASTER-Net observations report
  87. Fermi trigger No 766173972: Global MASTER-Net observations report
  88. Fermi GRB 250411A: Global MASTER-Net observations report
  89. GRB 250411A: Fermi GBM Final Real-time Localization
  90. EP250227a: Further NOT optical observations
  91. GRB 250320B: cubesat Avion detection
  92. IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
  93. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A
  94. IPN triangulation of GRB 250407A
  95. EP250407a: Global MASTER-Net observations report
  96. GRB 250407A: LCO detection of a fading optical counterpart
  97. Fermi-LAT gamma-ray observations of IceCube-250406A
  98. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  99. Konus-Wind detection of GRB 250407A
  100. GRB 250407A: SVOM/GRM observation of a bright long burst

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