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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

28261 results found.

  1. EP 250427A: Optical counterpart detection by LCO.
  2. GRB 250430A: Swift detection of a burst with optical counterpart
  3. EP250427a/GRB250427A: HCT optical follow-up
  4. SVOM/sb25043004: SVOM detection of a X-ray transient
  5. EP250428b: GROWTH-India telescope optical upper limit
  6. EP250428b: SAO RAS optical upper limit
  7. EP250428b: LAST optical upper limit
  8. GRB 250427A: Swift/UVOT Detection
  9. EP250428b: Global MASTER-Net observations report
  10. EP250428b: Einstein Probe detection of a fast X-ray transient
  11. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  12. EP250427a: Lesedi optical counterpart detection
  13. EP250427A: COLIBRÍ Continuing Optical Observations
  14. GRB250427A/EP250427a GIT optical afterglow detection:
  15. EP250427a: LT optical counterpart detection
  16. GRB 250427A: Swift-XRT refined Analysis
  17. EP250427a / GRB 250427A: LCO optical counterpart detection
  18. EP250427a: REM optical/NIR afterglow detection
  19. GRB 250424A: LCO optical observation
  20. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  21. EP250427A: COLIBRÍ Optical Detection
  22. EP250427a: TRT optical counterpart detection
  23. EP250427a: Einstein Probe detection of a fast X-ray transient
  24. GRB 250424A: Swift-BAT refined analysis
  25. GRB 250424A: SVOM/GRM observation of a long burst
  26. GRB 250424A: PRIME near-infrared detection
  27. GRB 250424A: WINTER J-band detection
  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 250419A: Mondy Optical Observations
  32. GRB 250424A: Swift/UVOT Detection
  33. Fermi-LAT gamma-ray observations of IceCube-250421A
  34. GRB 250424A: Skynet Optical Observations
  35. GRB 250424A: Kilonova-Catcher optical afterglow detection
  36. GRB 250330B: GRBAlpha detection
  37. GRB 250424A: Swift-XRT refined Analysis
  38. GRB 250424A: Enhanced Swift-XRT position
  39. GRB 250424A: AstroSat CZTI detection of a bright long burst
  40. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  41. GRB 250424A: BlackGEM optical afterglow detection
  42. GRB 250424A: DDOTI Afterglow Detection
  43. GRB 250424A: REM optical/NIR afterglow detection
  44. GRB 250424A: Swift detection of a burst with an optical counterpart
  45. Swift GRB 250424A: Global MASTER-Net OT detection
  46. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  47. EP250421a: Nickel optical upper limit
  48. EP250421a: Upper limits from Fermi-GBM Observations
  49. SVOM/sb25042207: SVOM detection of an X-ray transient
  50. IceCube-250421A: DDOTI Detection of the LAST Candidate
  51. GRB 250419A: Mephisto Multi-band Optical Detection
  52. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  53. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  54. EP250421a: NOT optical observations
  55. GRB 250419A: Optical Observations via Virtual Telescope Project
  56. EP250421a: REM optical upper limit
  57. EP250421A: COLIBRÍ Optical Upper Limit
  58. GRB 250419A: Mondy Continued Optical Observations
  59. GRB 250421B: AstroSat CZTI detection of a bright long burst
  60. EP250421a: Einstein Probe detection of an X-ray transient
  61. EP250421a: Mephisto optical counterpart confirmation
  62. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  63. EP250421a: JinShan likely optical counterpart
  64. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  65. GRB 250419A: LCO optical observation
  66. GRB 250419A: JinShan optical observations
  67. GRB 250419A: SVOM/C-GFT optical observations
  68. GRB 250419A: Swift/UVOT Follow up
  69. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  70. GRB 250419A: LCO optical afterglow multi-band observations
  71. GRB 250419A: Mondy and AbAO Optical Observations
  72. GRB 250419A: AKO Optical Afterglow Detection
  73. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  74. GRB 250419A: Swift-XRT refined Analysis
  75. GRB 250419A: KAIT optical afterglow observations
  76. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  77. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  78. GRB 250419A: SVOM detection of a soft burst
  79. EP250416a: Swift/XRT counterpart fading
  80. EP20250416a: Swift/XRT counterpart detection
  81. IceCube-250416A: DDOTI Optical Observations
  82. EP250416a: Gemini South-GMOS optical counterpart
  83. SVOM/sb25041603 is not a GRB
  84. EP250416a: GSP optical upper limit
  85. EP250416a: Einstein Probe detection of an X-ray transient
  86. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  87. SVOM/sb25041603: SVOM detection of an X-ray transient
  88. IceCube 250414.324: DDOTI Optical Observations
  89. GRB 250413A: AstroSat CZTI detection
  90. EP250304a: ATCA radio observations
  91. EP250404a: Nanshan 0.43m Telescope optical observatios
  92. GRB 250411A: DDOTI Optical Observations
  93. Fermi GRB 250411A: Global MASTER-Net observations report
  94. GRB 250407A: Continued KAIT/Nickel optical observations
  95. GRB 250314A: e-MERLIN observations
  96. GRB 250407A: Mondy and AbAO Optical Observations
  97. EP250227a: Further NOT optical observations
  98. GRB 250320B: cubesat Avion detection
  99. IceCube-250406A: Swift-XRT observations
  100. GRB 250407A: LCO detection of a fading optical counterpart

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