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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"
  1. LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations
  2. GRB 250129A: Skynet Continued Optical Observations
  3. GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
  4. EP250108A / SN 2025kg: Upper limits from a neutrino search with IceCube
  5. GRB 250129A: SAO RAS optical observations
  6. GRB 250129A: COLIBRÍ Continuing Detection of the Afterglow
  7. GRB 250129A: optical photometry from Konkoly
  8. GRB 250129A: COLIBRÍ Optical Observations
  9. GRB 250128B: VLA possible radio detection
  10. GRB 250129A: continued KAIT observations indicating steep decay after 28.5h
  11. GRB 250129A: iTelescope optical observation
  12. GRB 250129A: NOT optical observations of continuining activity
  13. GRB 250129a: Liverpool Telescope optical follow-up
  14. GRB 250129A: TNG NIR afterglow detection
  15. GRB 250129A: AKO Optical Afterglow Detection
  16. GRB 250129A: GRANDMA/TAROT optical afterglow detection
  17. GRB 250127A: EP-FXT second observation epoch and confirmation of the x-ray afterglow fading
  18. GRB 250128B: SAO RAS Zeiss-1000 and CrAO ZTSh optical upper limits
  19. GRB 250128B: VLA radio upper limit
  20. Ep250125A: 1.3m DFOT optical upper limit
  21. GRB 250129A: Skynet optical observations
  22. GRB 250129A: KAIT optical observations of the rebrightening around 5.1 hours
  23. GRB 250129A: Swift-XRT refined Analysis
  24. GRB 250128B: Gemini-North optical extended source detection
  25. The EP-WXT trigger 01709131085: KAIT confirmation of the stellar flare
  26. GRB 250128B: TNG optical upper limit
  27. GRB 250129A: Swift/UVOT Detection
  28. GRB 250128B: VLT/HAWKI near-infrared observations
  29. GRB 250127A: CrAO and Terskol optical upper limits
  30. GRB 250129A: Enhanced Swift-XRT position
  31. GRB 250128B: NOT optical upper limit
  32. GRB 250128B: VLT/FORS2 optical observations
  33. GRB 250129A: REM optical/NIR afterglow detection
  34. GRB 250129A: OHP/T193 optical and spectroscopy observations
  35. GRB 250129A: Early afterglow detection by LCO.
  36. GRB 250128B: OHP/T193 optical upper limit
  37. Swift GRB 250129A: Global MASTER-Net Slowly evolving LC detection
  38. GRB 250129A: LCO optical observations
  39. GRB 250129A: NOT optical observations and redshift confirmation
  40. GRB 250129A: GOTO optical observations show brightening afterglow
  41. GRB 250129A: VLT/X-shooter redshift of z = 2.151
  42. Swift GRB 250129A: Global MASTER-Net observations report
  43. GRB 250128B: Enhanced Swift-XRT position
  44. The EP-WXT trigger 01709131085 is likely a flaring star
  45. Fermi GRB 250128B: Global MASTER-Net observations report
  46. GRB 250129A: Swift detection of a burst with an optical counterpart
  47. Swift GRB 250129A: Global MASTER-Net OT detection
  48. GRB 250128B: Swift-XRT refined Analysis
  49. GRB 250128B: Fermi GBM Observation
  50. GRB 250128B: GOTO optical upper limit
  51. Swift GRB 250128B: Global MASTER-Net observations report
  52. EP250125a: Upper limits from Swift/BAT-GUANO
  53. GRB 250128B: LCO optical observations
  54. GRB 250128B: Swift detection of a short burst
  55. GRB 250128B: Fermi GBM Final Real-time Localization
  56. GRB 250127A: Swift-XRT observations
  57. GRB 250127B: DDOTI Upper Limit on the Afterglow
  58. Fermi-LAT Gamma-ray Observations of IceCube-250102A
  59. GRB 250127A: EP-FXT afterglow detection
  60. Fermi GRB 250128A: Global MASTER-Net observations report
  61. GRB 250128A: Fermi GBM Final Real-time Localization
  62. GRB 250117A: Fermi GBM Observation
  63. Fermi GRB 250127B: Global MASTER-Net observations report
  64. Fermi-LAT Gamma-ray Observations of IceCube-250101A
  65. GRB 250127A: SVOM/VT upper limit
  66. GRB 250127B: Fermi GBM Final Real-time Localization
  67. IPN triangulation of GRB 250119C
  68. GRB 250127A: Swift ToO observations
  69. GRB 250127A: LCO optical upper limit
  70. GRB 241223A: cubesat Avion detection
  71. GRB 250127A: SVOM detection of a long burst
  72. GRB 250126A: CALET Gamma-Ray Burst Monitor detection
  73. EP250125A: Non-detection from Fermi-GBM Observations
  74. GRB 250126A: MAXI/GSC detection
  75. EP250108a / SN 2025kg: Refined Analysis of EP-WXT Detection
  76. GRB 250126A: BALROG localization (Fermi Trigger 759560335 / GRB 250126208)
  77. GRB 250126A: Fermi GBM Final Real-time Localization
  78. GECAM-A detection of a bright burst from SGR 1E1841-045
  79. GRB 250118A: Fermi GBM Observation
  80. EP250125a: Optical upper limit with Kinder observations
  81. EP250125a: REM optical counterpart detection
  82. GRB 250119C: Fermi GBM Observation
  83. EP250125a: Swift/XRT detection of a fading counterpart
  84. EP250125a: a new X-ray transient detected by Einstein Probe
  85. EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
  86. The EP-WXT trigger 01709130758 is a false trigger
  87. The EP-WXT trigger 01709130758 is a false trigger
  88. Konus-Wind detection of a bright burst from SGR 1E1841-045 on 2025 January 23
  89. GRB 250121A: Swift/BAT-GUANO localization skymap of a burst
  90. IPN triangulation of a bright burst from SGR 1E1841-045
  91. GRB 250121A: CALET Gamma-Ray Burst Monitor detection
  92. EP250108a: AbAO, CMO and Terskol optical upper limits
  93. Konus-Wind detection of GRB 250118B
  94. GRB 250121A: Fermi GBM Observation
  95. IPN triangulation of GRB 250118B
  96. Konus-Wind detection of GRB 250119B
  97. IPN triangulation of GRB 250119B
  98. GRB 250122A: Fermi GBM Final Real-time Localization
  99. Improved IPN triangulation of GRB 250107C
  100. GRB 250114A: Swift-BAT refined analysis

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