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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"

43090 results found.

  1. GRB 250504A: Swift-XRT refined Analysis
  2. GRB 250504A: VLT/X-shooter upper limits
  3. Fermi GRB 250505A: Global MASTER-Net observations report
  4. GRB 250504A: SVOM/VT upper limit
  5. GRB 250504A: REM optical/NIR observations
  6. GRB 250502A: REM optical/NIR observations
  7. GRB 250505A: Fermi GBM Final Real-time Localization
  8. GRB 250504A: MeerLICHT optical afterglow detection
  9. GRB 250504A: Fermi GBM Observation
  10. GRB 250504A: Enhanced Swift-XRT position
  11. Fermi GRB 250504A: Global MASTER-Net observations report
  12. GRB 250504A: Swift detection of a burst
  13. GRB 250504A: Fermi GBM Final Real-time Localization
  14. Swift GRB250504.98: Global MASTER-Net observations report
  15. GRB 250502A: Mondy and Tien-Shan Optical Observations
  16. GRB 250502A: KAIT optical observations
  17. GRB 250502A: Montarrenti Observatory optical detection
  18. GRB 250502A: Swift-XRT afterglow detection
  19. Fermi trigger No 767975731: Global MASTER-Net observations report
  20. GRB 250502A: NOT optical observations
  21. GRB 250502a: Liverpool Telescope optical follow-up
  22. GRB 250502B: AstroSat CZTI detection
  23. GRB 250502A: AKO Optical Afterglow Detection
  24. GRB 250502A: LCO optical counterpart detection
  25. GRB 250502A: Swift ToO observations
  26. GRB 250502A: Redshift from OSIRIS+/GTC z = 2.163
  27. GRB 250502C: Fermi GBM Final Localization
  28. GRB 250407A: VZLUSAT-2 detection
  29. Fermi-LAT Gamma-ray Observations of IceCube-250429A
  30. GRB 250502B: DDOTI Optical Observations
  31. GRB 250430A: Swift-XRT refined Analysis
  32. GRB 250502A: Early optical counterpart detection by LCO.
  33. GRB 250430A: Swift/UVOT Detection
  34. GRB 250502A: SVOM/VT optical bump
  35. GRB 250502A: TRT optical afterglow confirmation
  36. GRB 250430A: Enhanced Swift-XRT position
  37. Fermi GRB 250502B: Global MASTER-Net observations report
  38. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  39. GRB 250502B: Fermi GBM Final Real-time Localization
  40. GRB 250502A: SVOM detection of a burst
  41. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  42. GRB 250430A: SVOM/VT optical observations
  43. GRB 250430A: KAIT optical observations
  44. EP250428b: Pan-STARRS follow-up, upper limit on the optical counterpart, and possible host galaxy.
  45. GRB 250430A / EP250430a: J-band upper limits with WINTER
  46. GRB 250430A: NUTTelA-TAO Early Measurements
  47. EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
  48. GRB 250430A: DDOTI Optical Observations
  49. GRB 250430A: Leavitt Observatory optical upper limit
  50. GRB 250430A: Bassano Bresciano Observatory upper limit
  51. GRB 250430A : MITSuME Akeno optical upper limits
  52. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  53. SVOM/sb25043004: EP-FXT observations
  54. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  55. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  56. IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
  57. IceCube-250426A: Upper limits from a search for additional neutrino events in IceCube
  58. GRB 250430A: AKO Optical Afterglow Detection
  59. EP 250427A: Optical counterpart detection by LCO.
  60. GRB 250430A: Swift detection of a burst with optical counterpart
  61. Swift GRB250430.73: Global MASTER-Net observations report
  62. EP250428b: FTW optical and NIR observations
  63. EP250427a/GRB250427A: HCT optical follow-up
  64. EP250427a / GRB 250427A: OHP/T193 continued photometric observations
  65. SVOM/sb25043004: SVOM detection of a X-ray transient
  66. Fermi trigger No 767623859: Global MASTER-Net observations report
  67. EP250428b: refined analysis of the EP-FXT follow-up observation
  68. EP250428b: GROWTH-India telescope optical upper limit
  69. EP250428b: SVOM/VT upper limit
  70. EP250428b: SAO RAS optical upper limit
  71. EP250428b: LAST optical upper limit
  72. IceCube-250429A - IceCube observation of a high-energy neutrino candidate track-like event
  73. GRB 250427A: Swift/UVOT Detection
  74. EP250428b: Global MASTER-Net observations report
  75. EP250428b: Einstein Probe detection of a fast X-ray transient
  76. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  77. EP250427a / GRB 250427A: OHP/T193 photometric observations
  78. EP250427a: EP-FXT follow-up observations
  79. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  80. EP250427a: Lesedi optical counterpart detection
  81. EP250427A: COLIBRÍ Continuing Optical Observations
  82. GRB250427A/EP250427a GIT optical afterglow detection:
  83. EP250427a: LT optical counterpart detection
  84. GRB 250427A: Swift-XRT refined Analysis
  85. EP250427a / GRB 250427A: LCO optical counterpart detection
  86. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  87. EP250427a: REM optical/NIR afterglow detection
  88. GRB 250424A: LCO optical observation
  89. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  90. EP250427A: COLIBRÍ Optical Detection
  91. EP250427a: TRT optical counterpart detection
  92. EP 250427a: BOOTES-7 optical afterglow candidate
  93. EP250427a: Global MASTER-Net observations report
  94. EP250427a: Einstein Probe detection of a fast X-ray transient
  95. IceCube Alert 250426.74: Global MASTER-Net observations report
  96. GRB 250424A: Swift-BAT refined analysis
  97. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event
  98. GRB 250424A: SVOM/GRM observation of a long burst
  99. GRB 250424A: PRIME near-infrared detection
  100. GRB 250424A: WINTER J-band detection

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