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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"

27186 results found.

  1. GRB 250506A: Swift XRT observations and possible counterpart detection
  2. GRB 250506A: TRT optical observations
  3. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
  4. GRB 250506A: SVOM detection of a burst
  5. GRB 250504A: Swift-BAT refined analysis
  6. GRB 250430A: Swift-BAT refined analysis
  7. GRB 250506A: Fermi GBM Final Real-time Localization
  8. GRB 250504A: Swift-XRT refined Analysis
  9. Fermi GRB 250505A: Global MASTER-Net observations report
  10. GRB 250504A: SVOM/VT upper limit
  11. GRB 250504A: REM optical/NIR observations
  12. GRB 250502A: REM optical/NIR observations
  13. GRB 250505A: Fermi GBM Final Real-time Localization
  14. GRB 250504A: MeerLICHT optical afterglow detection
  15. GRB 250504A: Fermi GBM Observation
  16. Fermi GRB 250504A: Global MASTER-Net observations report
  17. GRB 250504A: Swift detection of a burst
  18. GRB 250504A: Fermi GBM Final Real-time Localization
  19. Swift GRB250504.98: Global MASTER-Net observations report
  20. GRB 250502A: Swift/UVOT Follow up
  21. Fermi trigger No 767975731: Global MASTER-Net observations report
  22. GRB 250502A: NOT optical observations
  23. GRB 250502a: Liverpool Telescope optical follow-up
  24. GRB 250502A: AKO Optical Afterglow Detection
  25. GRB 250502A: LCO optical counterpart detection
  26. GRB 250502C: Fermi GBM Final Localization
  27. GRB 250502B: DDOTI Optical Observations
  28. GRB 250430A: Swift-XRT refined Analysis
  29. GRB 250502A: Early optical counterpart detection by LCO.
  30. GRB 250430A: Swift/UVOT Detection
  31. GRB 250502A: SVOM/VT optical bump
  32. GRB 250502A: TRT optical afterglow confirmation
  33. Fermi GRB 250502B: Global MASTER-Net observations report
  34. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  35. GRB 250502B: Fermi GBM Final Real-time Localization
  36. GRB 250502A: SVOM detection of a burst
  37. GRB 250430A: SVOM/VT optical observations
  38. GRB 250430A: KAIT optical observations
  39. GRB 250430A: NUTTelA-TAO Early Measurements
  40. EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
  41. GRB 250430A: DDOTI Optical Observations
  42. GRB 250430A: Leavitt Observatory optical upper limit
  43. GRB 250430A: Bassano Bresciano Observatory upper limit
  44. GRB 250430A : MITSuME Akeno optical upper limits
  45. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  46. SVOM/sb25043004: EP-FXT observations
  47. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  48. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  49. GRB 250430A: AKO Optical Afterglow Detection
  50. GRB 250430A: Kanata optical upper limit
  51. EP 250427A: Optical counterpart detection by LCO.
  52. GRB 250430A: Swift detection of a burst with optical counterpart
  53. Swift GRB250430.73: Global MASTER-Net observations report
  54. EP250428b: FTW optical and NIR observations
  55. EP250427a/GRB250427A: HCT optical follow-up
  56. EP250427a / GRB 250427A: OHP/T193 continued photometric observations
  57. SVOM/sb25043004: SVOM detection of a X-ray transient
  58. Fermi trigger No 767623859: Global MASTER-Net observations report
  59. EP250428b: refined analysis of the EP-FXT follow-up observation
  60. EP250428b: GROWTH-India telescope optical upper limit
  61. EP250428b: SVOM/VT upper limit
  62. EP250428b: Global MASTER-Net observations report
  63. EP250428b: Einstein Probe detection of a fast X-ray transient
  64. EP250427a / GRB 250427A: OHP/T193 photometric observations
  65. EP250427a: EP-FXT follow-up observations
  66. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  67. EP250427a: Lesedi optical counterpart detection
  68. EP250427A: COLIBRÍ Continuing Optical Observations
  69. GRB250427A/EP250427a GIT optical afterglow detection:
  70. GRB 250427A: Swift-XRT refined Analysis
  71. EP250427a / GRB 250427A: LCO optical counterpart detection
  72. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  73. EP250427a: REM optical/NIR afterglow detection
  74. GRB 250424A: LCO optical observation
  75. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  76. EP250427A: COLIBRÍ Optical Detection
  77. EP250427a: TRT optical counterpart detection
  78. EP250427a: Global MASTER-Net observations report
  79. EP250427a: Einstein Probe detection of a fast X-ray transient
  80. IceCube Alert 250426.74: Global MASTER-Net observations report
  81. GRB 250424A: Swift-BAT refined analysis
  82. GRB 250424A: SVOM/GRM observation of a long burst
  83. GRB 250424A: WINTER J-band detection
  84. GRB 250424A: EIRSAT-1 GMOD Detection
  85. GRB 250424A: SVOM/VT optical observation
  86. GRB 250419A: Mondy Optical Observations
  87. GRB 250424A: Swift/UVOT Detection
  88. GRB 250424A: Kilonova-Catcher optical afterglow detection
  89. GRB 250419a: Continued Liverpool Telescope observations
  90. GRB 250419A: Liverpool Telescope optical upper limit
  91. GRB 250330B: GRBAlpha detection
  92. GRB 250419A: SVOM/ECLAIRs refined analysis
  93. GRB 250424A: Swift-XRT refined Analysis
  94. GRB 250424A: AstroSat CZTI detection of a bright long burst
  95. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  96. GRB 250424A: BlackGEM optical afterglow detection
  97. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  98. GRB 250424A: DDOTI Afterglow Detection
  99. GRB 250424A: REM optical/NIR afterglow detection
  100. GRB 250424A: Swift detection of a burst with an optical counterpart

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