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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"

27921 results found.

  1. GRB 250502A: LCO optical counterpart detection
  2. GRB 250502A: Swift ToO observations
  3. GRB 250502C: Fermi GBM Final Localization
  4. GRB 250407A: VZLUSAT-2 detection
  5. GRB 250430A: Swift-XRT refined Analysis
  6. GRB 250502A: Early optical counterpart detection by LCO.
  7. GRB 250430A: Swift/UVOT Detection
  8. GRB 250430A: Enhanced Swift-XRT position
  9. GRB 250430A: Optical Observations via Virtual Telescope Project, Italy
  10. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  11. GRB 250502B: Fermi GBM Final Real-time Localization
  12. GRB 250502A: SVOM detection of a burst
  13. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  14. EP250428b: Pan-STARRS follow-up, upper limit on the optical counterpart, and possible host galaxy.
  15. EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
  16. GRB 250430A: DDOTI Optical Observations
  17. GRB 250430A: Leavitt Observatory optical upper limit
  18. GRB 250430A: Bassano Bresciano Observatory upper limit
  19. GRB 250430A : MITSuME Akeno optical upper limits
  20. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  21. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  22. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  23. GRB 250430A: AKO Optical Afterglow Detection
  24. EP 250427A: Optical counterpart detection by LCO.
  25. GRB 250430A: Swift detection of a burst with optical counterpart
  26. Swift GRB250430.73: Global MASTER-Net observations report
  27. SVOM/sb25043004: SVOM detection of a X-ray transient
  28. EP250428b: refined analysis of the EP-FXT follow-up observation
  29. IceCube-250429A - IceCube observation of a high-energy neutrino candidate track-like event
  30. GRB 250427A: Swift/UVOT Detection
  31. EP250428b: Einstein Probe detection of a fast X-ray transient
  32. EP250427a: EP-FXT follow-up observations
  33. EP250427a: Lesedi optical counterpart detection
  34. GRB250427A/EP250427a GIT optical afterglow detection:
  35. EP250427a: LT optical counterpart detection
  36. GRB 250427A: Swift-XRT refined Analysis
  37. EP250427a / GRB 250427A: LCO optical counterpart detection
  38. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  39. EP250427a: REM optical/NIR afterglow detection
  40. GRB 250424A: LCO optical observation
  41. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  42. EP250427A: COLIBRÍ Optical Detection
  43. EP250427a: TRT optical counterpart detection
  44. EP 250427a: BOOTES-7 optical afterglow candidate
  45. EP250427a: Einstein Probe detection of a fast X-ray transient
  46. GRB 250424A: Swift-BAT refined analysis
  47. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event
  48. GRB 250424A: SVOM/GRM observation of a long burst
  49. GRB 250424A: PRIME near-infrared detection
  50. GRB 250424A: WINTER J-band detection
  51. GRB 250424A: EIRSAT-1 GMOD Detection
  52. GRB 250424A: Swift/UVOT Detection
  53. Konus-Wind detection of GRB 250424A
  54. GRB 250424A: Skynet Optical Observations
  55. GRB 250424A: Kilonova-Catcher optical afterglow detection
  56. GRB 250419a: Continued Liverpool Telescope observations
  57. GRB 250407A: GRBAlpha detection
  58. GRB 250404A / EP250404a: GRBAlpha detection
  59. GRB 250330B: GRBAlpha detection
  60. GRB 250424A: Swift-XRT refined Analysis
  61. GRB 250424A: Enhanced Swift-XRT position
  62. GRB 250424A: AstroSat CZTI detection of a bright long burst
  63. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  64. GRB 250424A: BlackGEM optical afterglow detection
  65. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  66. GRB 250424A: likely host galaxy
  67. GRB 250424A: DDOTI Afterglow Detection
  68. GRB 250424A: REM optical/NIR afterglow detection
  69. GRB 250424A: Swift detection of a burst with an optical counterpart
  70. Swift GRB 250424A: Global MASTER-Net observations report
  71. Swift GRB 250424A: Global MASTER-Net OT detection
  72. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  73. SVOM/sb25042207: XRT observations
  74. SVOM/sb25042207: BOOTES-2 early optical upper limit
  75. GRB 250421A: AstroSat CZTI detection
  76. SVOM/sb25042207: SVOM detection of an X-ray transient
  77. GRB250419A: VLA radio detection
  78. IceCube-250421A: DDOTI Detection of the LAST Candidate
  79. GRB 250419A: Mephisto Multi-band Optical Detection
  80. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  81. EP250421a: NOT optical observations
  82. GRB 250419A: Optical Observations via Virtual Telescope Project
  83. EP250421a: Swift/XRT counterpart detection
  84. GRB 250421B: AstroSat CZTI detection of a bright long burst
  85. EP250421a: Einstein Probe detection of an X-ray transient
  86. EP250421a: Mephisto optical counterpart confirmation
  87. IceCube-250421A - IceCube observation of a high-energy neutrino candidate track-like event
  88. GRB 250421A: Fermi GBM Final Real-time Localization
  89. GRB 250419A: Liverpool Telescope observations
  90. GRB 250419A: Swift/UVOT Follow up
  91. GRB 250419A: LCO optical afterglow multi-band observations
  92. GRB 250419A: Mondy and AbAO Optical Observations
  93. GRB 250419A: AKO Optical Afterglow Detection
  94. GRB 250419A: Swift-XRT localisation
  95. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  96. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  97. GRB 250419A: Swift-XRT refined Analysis
  98. GRB 250419A: GOTO optical counterpart detection
  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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