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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"

28279 results found.

  1. GRB 250502A: SVOM detection of a burst
  2. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  3. GRB 250430A: KAIT optical observations
  4. GRB 250430A / EP250430a: J-band upper limits with WINTER
  5. GRB 250430A: NUTTelA-TAO Early Measurements
  6. GRB 250430A: DDOTI Optical Observations
  7. GRB 250430A: Leavitt Observatory optical upper limit
  8. GRB 250430A: Bassano Bresciano Observatory upper limit
  9. GRB 250430A : MITSuME Akeno optical upper limits
  10. SVOM/sb25043004: EP-FXT observations
  11. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  12. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  13. IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
  14. IceCube-250426A: Upper limits from a search for additional neutrino events in IceCube
  15. GRB 250430A: AKO Optical Afterglow Detection
  16. GRB 250430A: Kanata optical upper limit
  17. EP 250427A: Optical counterpart detection by LCO.
  18. GRB 250430A: Swift detection of a burst with optical counterpart
  19. EP250427a/GRB250427A: HCT optical follow-up
  20. SVOM/sb25043004: SVOM detection of a X-ray transient
  21. EP250428b: GROWTH-India telescope optical upper limit
  22. EP250428b: SAO RAS optical upper limit
  23. EP250428b: LAST optical upper limit
  24. GRB 250427A: Swift/UVOT Detection
  25. EP250428b: Global MASTER-Net observations report
  26. EP250428b: Einstein Probe detection of a fast X-ray transient
  27. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  28. EP250427a: Lesedi optical counterpart detection
  29. EP250427A: COLIBRÍ Continuing Optical Observations
  30. GRB250427A/EP250427a GIT optical afterglow detection:
  31. EP250427a: LT optical counterpart detection
  32. GRB 250427A: Swift-XRT refined Analysis
  33. EP250427a / GRB 250427A: LCO optical counterpart detection
  34. EP250427a: REM optical/NIR afterglow detection
  35. GRB 250424A: LCO optical observation
  36. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  37. EP250427A: COLIBRÍ Optical Detection
  38. EP250427a: TRT optical counterpart detection
  39. EP250427a: Einstein Probe detection of a fast X-ray transient
  40. GRB 250424A: Swift-BAT refined analysis
  41. GRB 250424A: SVOM/GRM observation of a long burst
  42. GRB 250424A: PRIME near-infrared detection
  43. GRB 250424A: WINTER J-band detection
  44. GRB 250424A: EIRSAT-1 GMOD Detection
  45. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  46. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  47. GRB 250419A: Mondy Optical Observations
  48. GRB 250424A: Swift/UVOT Detection
  49. Fermi-LAT gamma-ray observations of IceCube-250421A
  50. GRB 250424A: Skynet Optical Observations
  51. GRB 250424A: Kilonova-Catcher optical afterglow detection
  52. GRB 250330B: GRBAlpha detection
  53. GRB 250424A: Swift-XRT refined Analysis
  54. GRB 250424A: Enhanced Swift-XRT position
  55. GRB 250424A: AstroSat CZTI detection of a bright long burst
  56. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  57. GRB 250424A: BlackGEM optical afterglow detection
  58. GRB 250424A: DDOTI Afterglow Detection
  59. GRB 250424A: REM optical/NIR afterglow detection
  60. GRB 250424A: Swift detection of a burst with an optical counterpart
  61. Swift GRB 250424A: Global MASTER-Net OT detection
  62. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  63. EP250421a: Nickel optical upper limit
  64. EP250421a: Upper limits from Fermi-GBM Observations
  65. SVOM/sb25042207: SVOM detection of an X-ray transient
  66. IceCube-250421A: DDOTI Detection of the LAST Candidate
  67. GRB 250419A: Mephisto Multi-band Optical Detection
  68. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  69. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  70. EP250421a: NOT optical observations
  71. GRB 250419A: Optical Observations via Virtual Telescope Project
  72. EP250421a: REM optical upper limit
  73. EP250421A: COLIBRÍ Optical Upper Limit
  74. GRB 250419A: Mondy Continued Optical Observations
  75. GRB 250421B: AstroSat CZTI detection of a bright long burst
  76. EP250421a: Einstein Probe detection of an X-ray transient
  77. EP250421a: Mephisto optical counterpart confirmation
  78. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  79. EP250421a: JinShan likely optical counterpart
  80. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  81. GRB 250419A: LCO optical observation
  82. GRB 250419A: JinShan optical observations
  83. GRB 250419A: SVOM/C-GFT optical observations
  84. GRB 250419A: Swift/UVOT Follow up
  85. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  86. GRB 250419A: LCO optical afterglow multi-band observations
  87. GRB 250419A: Mondy and AbAO Optical Observations
  88. GRB 250419A: AKO Optical Afterglow Detection
  89. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  90. GRB 250419A: Swift-XRT refined Analysis
  91. GRB 250419A: KAIT optical afterglow observations
  92. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  93. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  94. GRB 250419A: SVOM detection of a soft burst
  95. EP250416a: Swift/XRT counterpart fading
  96. EP20250416a: Swift/XRT counterpart detection
  97. IceCube-250416A: DDOTI Optical Observations
  98. EP250416a: Gemini South-GMOS optical counterpart
  99. SVOM/sb25041603 is not a GRB
  100. EP250416a: GSP optical upper limit

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