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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"

21934 results found.

  1. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  2. EP250511a: Gemini optical counterpart observation
  3. EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
  4. EP250512a/GRB 250512B: FTW optical and NIR observations of the counterpart
  5. EP250512a: Global MASTER-Net observations report
  6. EP250511a: FTW optical and NIR observations
  7. GRB 250512B/EP250512a:SVOM/VT bright optical counterpart
  8. EP250511a: Mephisto optical upper limits
  9. EP250511a: REM optical/NIR observations
  10. EP250511a: SVOM/VT optical candidate comfirmation
  11. EP250511a: Global MASTER-Net observations report
  12. EP250511a: COLIBRÍ optical counterpart candidate
  13. EP250508a: Gemini NIR upper limits
  14. Fermi GRB 250510C: Global MASTER-Net observations report
  15. Fermi GRB 250510B: Global MASTER-Net observations report
  16. GRB 250510A: Swift-XRT observations
  17. IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
  18. GRB 250510A: follow-up observation with EP-FXT
  19. GRB 250510B: Swift/BAT-GUANO localization skymap of a burst
  20. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  21. GRB 250507A: J-band observations with WINTER (duplicate submission)
  22. GRB 250507A: J-band observations with WINTER
  23. Fermi GRB 250509A: Global MASTER-Net observations report
  24. Swift GRB 250509A: Global MASTER-Net observations report
  25. EP250508a: follow-up observation with EP-FXT
  26. GRB 250507A: KAIT optical upper limit
  27. EP250508a: refined analysis of the EP-WXT and EP-FXT observations
  28. GRB 250502A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  29. EP250508a: REM optical/NIR observations
  30. GRB 250506A: Swift-XRT afterglow detection
  31. EP250508a: Global MASTER-Net observations report
  32. GRB 250506A: SVOM/VT optical upper limit
  33. EP250508a: COLIBRÍ Optical Limit
  34. GRB 250506A: Swift/UVOT Upper Limits
  35. EP#01709175213/IGR J19566+0326: Swift-XRT detection
  36. GRB 250507A: refined SVOM/MXT data analysis
  37. GRB 250507A: REM optical/NIR observations
  38. GRB 250507A: SVOM/VT optical upper limit
  39. GRB 250506A: Swift-XRT observations
  40. Fermi-LAT Gamma-ray Observations of IceCube-250506A
  41. GRB 250507A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  42. GRB 250506A: Mephisto optical upper limits
  43. GRB 250506A: Swift ToO observations
  44. GRB 250502A: Bassano Bresciano Observatory upper limit
  45. IceCube Alert 250506.59: Global MASTER-Net observations report
  46. SVOM/sb25050601: EP-FXT observations
  47. GRB 250506A: REM optical/NIR upper limits
  48. GRB 250506A: Swift XRT observations and possible counterpart detection
  49. GRB 250506A: TRT optical observations
  50. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
  51. Fermi GRB 250505A: Global MASTER-Net observations report
  52. GRB 250504A: SVOM/VT upper limit
  53. GRB 250504A: REM optical/NIR observations
  54. GRB 250502A: REM optical/NIR observations
  55. GRB 250504A: MeerLICHT optical afterglow detection
  56. Fermi GRB 250504A: Global MASTER-Net observations report
  57. Swift GRB250504.98: Global MASTER-Net observations report
  58. GRB 250502A: Swift/UVOT Follow up
  59. GRB 250502A: Mondy and Tien-Shan Optical Observations
  60. GRB 250502A: KAIT optical observations
  61. GRB 250502A: Montarrenti Observatory optical detection
  62. GRB 250502A: Swift-XRT afterglow detection
  63. Fermi trigger No 767975731: Global MASTER-Net observations report
  64. GRB 250502A: NOT optical observations
  65. GRB 250502a: Liverpool Telescope optical follow-up
  66. GRB 250502A: LCO optical counterpart detection
  67. GRB 250502A: Swift ToO observations
  68. Fermi-LAT Gamma-ray Observations of IceCube-250429A
  69. GRB 250502B: DDOTI Optical Observations
  70. GRB 250502A: Early optical counterpart detection by LCO.
  71. GRB 250430A: Swift/UVOT Detection
  72. GRB 250502A: SVOM/VT optical bump
  73. GRB 250502A: TRT optical afterglow confirmation
  74. Fermi GRB 250502B: Global MASTER-Net observations report
  75. GRB 250430A: Optical Observations via Virtual Telescope Project, Italy
  76. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  77. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  78. GRB 250430A: SVOM/VT optical observations
  79. GRB 250430A: KAIT optical observations
  80. EP250428b: Pan-STARRS follow-up, upper limit on the optical counterpart, and possible host galaxy.
  81. GRB 250430A / EP250430a: J-band upper limits with WINTER
  82. GRB 250430A: NUTTelA-TAO Early Measurements
  83. EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
  84. GRB 250430A: DDOTI Optical Observations
  85. GRB 250430A: Leavitt Observatory optical upper limit
  86. GRB 250430A: Bassano Bresciano Observatory upper limit
  87. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  88. SVOM/sb25043004: EP-FXT observations
  89. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  90. EP 250427A: Optical counterpart detection by LCO.
  91. Swift GRB250430.73: Global MASTER-Net observations report
  92. EP250428b: FTW optical and NIR observations
  93. EP250427a/GRB250427A: HCT optical follow-up
  94. EP250427a / GRB 250427A: OHP/T193 continued photometric observations
  95. Fermi trigger No 767623859: Global MASTER-Net observations report
  96. EP250428b: SVOM/VT upper limit
  97. EP250428b: LAST optical upper limit
  98. EP250428b: Global MASTER-Net observations report
  99. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  100. EP250427a / GRB 250427A: OHP/T193 photometric observations

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