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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"

24785 results found.

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

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