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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"

27555 results found.

  1. GRB 250506A: Swift XRT observations and possible counterpart detection
  2. GRB 250506A: TRT optical observations
  3. GRB 250506A: SVOM detection of a burst
  4. GRB 250506A: Fermi GBM Final Real-time Localization
  5. GRB 250504A: Swift-XRT refined Analysis
  6. GRB 250504A: VLT/X-shooter upper limits
  7. GRB 250504A: SVOM/VT upper limit
  8. GRB 250504A: REM optical/NIR observations
  9. GRB 250502A: REM optical/NIR observations
  10. GRB 250505A: Fermi GBM Final Real-time Localization
  11. GRB 250504A: MeerLICHT optical afterglow detection
  12. GRB 250504A: Enhanced Swift-XRT position
  13. GRB 250504A: Swift detection of a burst
  14. GRB 250504A: Fermi GBM Final Real-time Localization
  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. GRB 250502a: Liverpool Telescope optical follow-up
  20. GRB 250502B: AstroSat CZTI detection
  21. GRB 250502A: AKO Optical Afterglow Detection
  22. GRB 250502A: LCO optical counterpart detection
  23. GRB 250502A: Swift ToO observations
  24. GRB 250502A: Redshift from OSIRIS+/GTC z = 2.163
  25. GRB 250502C: Fermi GBM Final Localization
  26. GRB 250407A: VZLUSAT-2 detection
  27. GRB 250430A: Swift-XRT refined Analysis
  28. GRB 250502A: Early optical counterpart detection by LCO.
  29. GRB 250430A: Swift/UVOT Detection
  30. GRB 250502A: TRT optical afterglow confirmation
  31. GRB 250430A: Enhanced Swift-XRT position
  32. GRB 250430A: Optical Observations via Virtual Telescope Project, Italy
  33. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  34. GRB 250502B: Fermi GBM Final Real-time Localization
  35. GRB 250502A: SVOM detection of a burst
  36. GRB 250430A: SVOM/VT optical observations
  37. GRB 250430A: KAIT optical observations
  38. EP250428b: Pan-STARRS follow-up, upper limit on the optical counterpart, and possible host galaxy.
  39. GRB 250430A: NUTTelA-TAO Early Measurements
  40. EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
  41. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  42. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  43. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  44. GRB 250430A: AKO Optical Afterglow Detection
  45. EP 250427A: Optical counterpart detection by LCO.
  46. GRB 250430A: Swift detection of a burst with optical counterpart
  47. EP250427a / GRB 250427A: OHP/T193 continued photometric observations
  48. SVOM/sb25043004: SVOM detection of a X-ray transient
  49. EP250428b: refined analysis of the EP-FXT follow-up observation
  50. IceCube-250429A - IceCube observation of a high-energy neutrino candidate track-like event
  51. GRB 250427A: Swift/UVOT Detection
  52. EP250428b: Einstein Probe detection of a fast X-ray transient
  53. EP250427a / GRB 250427A: OHP/T193 photometric observations
  54. EP250427a: EP-FXT follow-up observations
  55. EP250427a: Lesedi optical counterpart detection
  56. GRB250427A/EP250427a GIT optical afterglow detection:
  57. EP250427a: LT optical counterpart detection
  58. GRB 250427A: Swift-XRT refined Analysis
  59. EP250427a / GRB 250427A: LCO optical counterpart detection
  60. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  61. EP250427A/GRB250427A: Keck/LRIS redshift
  62. EP250427a: REM optical/NIR afterglow detection
  63. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  64. EP250427A: COLIBRÍ Optical Detection
  65. EP250427a: TRT optical counterpart detection
  66. EP 250427a: BOOTES-7 optical afterglow candidate
  67. EP250427a: Einstein Probe detection of a fast X-ray transient
  68. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event
  69. GRB 250424A: PRIME near-infrared detection
  70. GRB 250424A: WINTER J-band detection
  71. GRB 250424A: EIRSAT-1 GMOD Detection
  72. GRB 250424A: Swift/UVOT Detection
  73. Konus-Wind detection of GRB 250424A
  74. GRB 250424A: Skynet Optical Observations
  75. GRB 250424A: Kilonova-Catcher optical afterglow detection
  76. GRB 250419a: Continued Liverpool Telescope observations
  77. GRB 250419A: Liverpool Telescope optical upper limit
  78. GRB 250407A: GRBAlpha detection
  79. GRB 250404A / EP250404a: GRBAlpha detection
  80. GRB 250330B: GRBAlpha detection
  81. GRB 250424A: Swift-XRT refined Analysis
  82. GRB 250424A: Enhanced Swift-XRT position
  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 OT detection
  92. EP250421a: Nickel optical upper limit
  93. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  94. SVOM/sb25042207: XRT observations
  95. SVOM/sb25042207: BOOTES-2 early optical upper limit
  96. GRB 250421A: AstroSat CZTI detection
  97. SVOM/sb25042207: SVOM detection of an X-ray transient
  98. GRB250419A: VLA radio detection
  99. IceCube-250421A: DDOTI Detection of the LAST Candidate
  100. GRB 250419A: Mephisto Multi-band Optical Detection

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