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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"

26119 results found.

  1. GRB 250504A: SVOM/VT upper limit
  2. GRB 250504A: REM optical/NIR observations
  3. GRB 250502A: REM optical/NIR observations
  4. GRB 250504A: MeerLICHT optical afterglow detection
  5. GRB 250504A: Fermi GBM Observation
  6. GRB 250504A: Enhanced Swift-XRT position
  7. GRB 250504A: Swift detection of a burst
  8. Swift GRB250504.98: Global MASTER-Net observations report
  9. GRB 250502A: Swift/UVOT Follow up
  10. GRB 250502A: Mondy and Tien-Shan Optical Observations
  11. GRB 250502A: KAIT optical observations
  12. GRB 250502A: Montarrenti Observatory optical detection
  13. GRB 250502A: Swift-XRT afterglow detection
  14. GRB 250502a: Liverpool Telescope optical follow-up
  15. GRB 250502A: AKO Optical Afterglow Detection
  16. GRB 250502A: Swift ToO observations
  17. GRB 250502A: Redshift from OSIRIS+/GTC z = 2.163
  18. GRB 250430A: Swift-XRT refined Analysis
  19. GRB 250430A: Swift/UVOT Detection
  20. GRB 250502A: TRT optical afterglow confirmation
  21. GRB 250430A: Enhanced Swift-XRT position
  22. GRB 250430A: Optical Observations via Virtual Telescope Project, Italy
  23. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  24. GRB 250430A: SVOM/VT optical observations
  25. GRB 250430A: KAIT optical observations
  26. GRB 250430A: NUTTelA-TAO Early Measurements
  27. EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
  28. GRB 250430A: DDOTI Optical Observations
  29. GRB 250430A: Leavitt Observatory optical upper limit
  30. GRB 250430A: Bassano Bresciano Observatory upper limit
  31. GRB 250430A : MITSuME Akeno optical upper limits
  32. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  33. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  34. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  35. GRB 250430A: AKO Optical Afterglow Detection
  36. GRB 250430A: Swift detection of a burst with optical counterpart
  37. Swift GRB250430.73: Global MASTER-Net observations report
  38. EP250427a / GRB 250427A: OHP/T193 continued photometric observations
  39. GRB 250427A: Swift/UVOT Detection
  40. EP250427a / GRB 250427A: OHP/T193 photometric observations
  41. EP250427a: EP-FXT follow-up observations
  42. GRB250427A/EP250427a GIT optical afterglow detection:
  43. GRB 250427A: Swift-XRT refined Analysis
  44. EP250427A/GRB250427A: Keck/LRIS redshift
  45. EP250427a: REM optical/NIR afterglow detection
  46. GRB 250424A: LCO optical observation
  47. EP 250427a: BOOTES-7 optical afterglow candidate
  48. GRB 250424A: Swift-BAT refined analysis
  49. GRB 250424A: SVOM/GRM observation of a long burst
  50. GRB 250424A: PRIME near-infrared detection
  51. GRB 250424A: WINTER J-band detection
  52. GRB 250424A: EIRSAT-1 GMOD Detection
  53. GRB 250424A: Swift/UVOT Detection
  54. Konus-Wind detection of GRB 250424A
  55. GRB 250424A: Skynet Optical Observations
  56. GRB 250424A: Kilonova-Catcher optical afterglow detection
  57. GRB 250419a: Continued Liverpool Telescope observations
  58. GRB 250419A: Liverpool Telescope optical upper limit
  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: VLT/X-shooter spectroscopic redshift z = 0.310
  65. GRB 250424A: likely host galaxy
  66. GRB 250424A: DDOTI Afterglow Detection
  67. GRB 250424A: REM optical/NIR afterglow detection
  68. GRB 250424A: Swift detection of a burst with an optical counterpart
  69. Swift GRB 250424A: Global MASTER-Net observations report
  70. Swift GRB 250424A: Global MASTER-Net OT detection
  71. EP250421a: Nickel optical upper limit
  72. SVOM/sb25042207: XRT observations
  73. GRB250419A: VLA radio detection
  74. EP250421a: NOT optical observations
  75. GRB 250419A: Optical Observations via Virtual Telescope Project
  76. EP250421a: REM optical upper limit
  77. EP250421a: Swift/XRT counterpart detection
  78. GRB 250419A: JinShan optical observations
  79. GRB 250419A: Swift/UVOT Follow up
  80. GRB 250419A: LCO optical afterglow multi-band observations
  81. GRB 250419A: Mondy and AbAO Optical Observations
  82. GRB 250419A: AKO Optical Afterglow Detection
  83. GRB 250419A: MASTER optical afterglow observation
  84. GRB 250419A: Swift-XRT localisation
  85. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  86. GRB 250419A: Swift-XRT refined Analysis
  87. GRB 250419A: GOTO optical counterpart detection
  88. GRB 250419A: KAIT optical afterglow observations
  89. EP250416a: Swift/XRT counterpart fading
  90. EP250416a: refined EP-WXT and EP-FXT analysis
  91. EP20250416a: Swift/XRT counterpart detection
  92. EP250416a: Gemini South-GMOS optical counterpart
  93. EP250404a: Nanshan 0.43m Telescope optical observatios
  94. GRB 250407A: Continued KAIT/Nickel optical observations
  95. GRB 250407A: Mondy and AbAO Optical Observations
  96. IceCube-250406A: Swift-XRT observations
  97. IPN triangulation of GRB 250407A
  98. GRB 250407A: LCO detection of a fading optical counterpart
  99. EP250407a: Swift-XRT observations
  100. Konus-Wind detection of GRB 250407A

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