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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. 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"

24167 results found.

  1. GRB 250506A: Fermi GBM Final Real-time Localization
  2. GRB 250504A: Swift-XRT refined Analysis
  3. GRB 250504A: VLT/X-shooter upper limits
  4. Fermi GRB 250505A: Global MASTER-Net observations report
  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. Fermi GRB 250504A: Global MASTER-Net observations report
  11. GRB 250504A: Swift detection of a burst
  12. GRB 250504A: Fermi GBM Final Real-time Localization
  13. Swift GRB250504.98: Global MASTER-Net observations report
  14. GRB 250502A: Swift/UVOT Follow up
  15. Fermi trigger No 767975731: Global MASTER-Net observations report
  16. GRB 250502A: NOT optical observations
  17. GRB 250502a: Liverpool Telescope optical follow-up
  18. GRB 250502A: AKO Optical Afterglow Detection
  19. GRB 250502A: LCO optical counterpart detection
  20. GRB 250502C: Fermi GBM Final Localization
  21. GRB 250502B: DDOTI Optical Observations
  22. GRB 250430A: Swift-XRT refined Analysis
  23. GRB 250502A: Early optical counterpart detection by LCO.
  24. GRB 250430A: Swift/UVOT Detection
  25. GRB 250502A: TRT optical afterglow confirmation
  26. Fermi GRB 250502B: Global MASTER-Net observations report
  27. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  28. GRB 250502B: Fermi GBM Final Real-time Localization
  29. GRB 250502A: SVOM detection of a burst
  30. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  31. GRB 250430A: KAIT optical observations
  32. GRB 250430A: NUTTelA-TAO Early Measurements
  33. EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
  34. GRB 250430A: DDOTI Optical Observations
  35. GRB 250430A: Leavitt Observatory optical upper limit
  36. GRB 250430A: Bassano Bresciano Observatory upper limit
  37. GRB 250430A : MITSuME Akeno optical upper limits
  38. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  39. SVOM/sb25043004: EP-FXT observations
  40. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  41. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  42. GRB 250430A: AKO Optical Afterglow Detection
  43. GRB 250430A: Kanata optical upper limit
  44. EP 250427A: Optical counterpart detection by LCO.
  45. GRB 250430A: Swift detection of a burst with optical counterpart
  46. Swift GRB250430.73: Global MASTER-Net observations report
  47. EP250428b: FTW optical and NIR observations
  48. EP250427a/GRB250427A: HCT optical follow-up
  49. EP250427a / GRB 250427A: OHP/T193 continued photometric observations
  50. SVOM/sb25043004: SVOM detection of a X-ray transient
  51. Fermi trigger No 767623859: Global MASTER-Net observations report
  52. EP250428b: GROWTH-India telescope optical upper limit
  53. EP250428b: Global MASTER-Net observations report
  54. EP250427a / GRB 250427A: OHP/T193 photometric observations
  55. EP250427a: EP-FXT follow-up observations
  56. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  57. EP250427a: Lesedi optical counterpart detection
  58. EP250427A: COLIBRÍ Continuing Optical Observations
  59. GRB250427A/EP250427a GIT optical afterglow detection:
  60. GRB 250427A: Swift-XRT refined Analysis
  61. EP250427a / GRB 250427A: LCO optical counterpart detection
  62. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  63. EP250427a: REM optical/NIR afterglow detection
  64. GRB 250424A: LCO optical observation
  65. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  66. EP250427A: COLIBRÍ Optical Detection
  67. EP250427a: TRT optical counterpart detection
  68. EP250427a: Global MASTER-Net observations report
  69. IceCube Alert 250426.74: Global MASTER-Net observations report
  70. GRB 250424A: Swift-BAT refined analysis
  71. GRB 250424A: SVOM/GRM observation of a long burst
  72. GRB 250424A: PRIME near-infrared detection
  73. GRB 250424A: WINTER J-band detection
  74. GRB 250424A: EIRSAT-1 GMOD Detection
  75. GRB 250419A: Mondy Optical Observations
  76. GRB 250424A: Swift/UVOT Detection
  77. Konus-Wind detection of GRB 250424A
  78. GRB 250424A: Kilonova-Catcher optical afterglow detection
  79. GRB 250419a: Continued Liverpool Telescope observations
  80. GRB 250419A: Liverpool Telescope optical upper limit
  81. GRB 250330B: GRBAlpha detection
  82. GRB 250424A: Swift-XRT refined Analysis
  83. GRB 250424A: AstroSat CZTI detection of a bright long burst
  84. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  85. GRB 250424A: BlackGEM optical afterglow detection
  86. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  87. GRB 250424A: likely host galaxy
  88. GRB 250424A: DDOTI Afterglow Detection
  89. GRB 250424A: REM optical/NIR afterglow detection
  90. GRB 250424A: Swift detection of a burst with an optical counterpart
  91. Swift GRB 250424A: Global MASTER-Net observations report
  92. Swift GRB 250424A: Global MASTER-Net OT detection
  93. EP250421a: Nickel optical upper limit
  94. EP250421a: Upper limits from Fermi-GBM Observations
  95. SVOM/sb25042207: XRT observations
  96. SVOM/sb25042207: GOTO optical upper limits
  97. SVOM/sb25042207: SVOM detection of an X-ray transient
  98. IceCube-250421A: DDOTI Detection of the LAST Candidate
  99. GRB 250419A: Mephisto Multi-band Optical Detection
  100. EP250421a: NOT optical observations

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