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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"

26037 results found.

  1. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  2. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  3. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  4. Swift BAT trigger 1500295: A solar flare
  5. Swift BAT trigger 1500287: A solar flare
  6. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  7. GRB260310A / AT2026fgk: P200 Spectroscopy
  8. Swift BAT trigger 1500148: A solar flare
  9. Retraction of GCN 43965: GRB is actually solar flare
  10. GRB 260312A: Swift detection of a burst
  11. GRB 260208A: radio detection with the VLA
  12. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  13. EP260302a: Optical afterglow rebrightening
  14. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  15. GRB 260303A: SVOM/VT optical observations
  16. EP260227A: 3.6m DOT optical afterglow detection
  17. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  18. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  19. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  20. IPN triangulation of GRB 260212A
  21. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  22. Swift Operations Update + Community Forum (Friday, February 13 @ 10:00 AM EST)
  23. GRB 260208A: Swift UVOT detection
  24. GRB 260208A: LCO detection of the optical counterpart
  25. GRB 260208B: refined analysis of the EP-FXT observation
  26. GRB 260204A: Swift-XRT afterglow detection
  27. GRB 260208A: Fermi GBM Observation
  28. GRB 260208B: Swift-XRT observations
  29. GRB 260204A: Swift/UVOT Upper Limits
  30. GRB 260208A: 1.3m DFOT optical detection
  31. GRB 260208B: EP-FXT observation
  32. GRB 260208B: SVOM/VT optical candidate
  33. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  34. GRB 260208A: SVOM/VT optical observation
  35. GRB 260208A: Swift-XRT observations
  36. GRB 260208B: Swift ToO observations
  37. GRB 260208B: Fermi-LAT detection
  38. GRB 260208A: Fermi-LAT detection
  39. GRB 260208A: Swift ToO observations
  40. GRB 260208A: Fermi GBM Classification Correction
  41. GRB 260206A: Swift-XRT observations
  42. EP260131a: VLA detection
  43. GRB 260206A: Tiled Swift observations
  44. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  45. GRB 260204A: Swift-XRT observations
  46. GRB 260204A: LCO optical afterglow detection
  47. GRB 260204A: SVOM/VT optical candidate
  48. GRB 260131A/B: OHP/T193 optical observations
  49. GRB 260131A: KAIT optical observations
  50. GRB 251230A: MeerLICHT afterglow detection
  51. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  52. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  53. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  54. GRB 260131A/B: EP/FXT X-ray afterglow detection
  55. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  56. GRB 260127A: GECAM-B observation
  57. GRB 260131A: NOT spectroscopic redshift z = 1.434
  58. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  59. GRB 260127B: AstroSat CZTI detection
  60. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  61. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  62. IPN triangulation of GRB 260121A
  63. GRB 260127A: Swift-BAT refined analysis
  64. GRB 260127B: Swift-XRT observations
  65. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  66. GRB 260127A: Fermi GBM Observation
  67. GRB 260127A: COLIBRÍ optical observations
  68. GRB 260127B: Swift ToO observations
  69. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  70. GRB 260127A: Swift-XRT refined Analysis
  71. GRB 260127A: SVOM/C-GFT optical observations
  72. GRB 260127A: Enhanced Swift-XRT position
  73. GRB 260127A: Prompt enhanced Swift-XRT position
  74. Swift GRB 260127A: Global MASTER-Net observations report
  75. GRB 260127A: LCO optical afterglow discovery
  76. GRB 260127A: Swift detection of a burst
  77. GRB 260125A: Swift-XRT observations
  78. Konus-Wind detection of GRB 260120B
  79. GRB 260125A: Swift ToO observations
  80. GRB 260114A: SVOM/VT optical upper limits
  81. GRB 260122B: Swift-BAT refined analysis
  82. GRB 260120B: SVOM/GRM observation
  83. GRB 260120B: AstroSat CZTI detection
  84. GRB 260114A: Insight-HXMT/HE detection
  85. GRB 260122B: Swift detection of a burst
  86. Swift GRB260122.97: Global MASTER-Net observations report
  87. GRB 260120B: Swift-BAT refined analysis
  88. GRB 260120B: Swift-XRT refined Analysis
  89. GRB 260120B: Fermi GBM Observation
  90. GRB 260120B: Swift/UVOT Detection
  91. GRB 260120B: COLIBRÍ optical upper limits
  92. GRB 260120B: Enhanced Swift-XRT position
  93. GRB 260120B: SVOM/C-GFT optical counterpart detection
  94. GRB 260101A: 239Alferov CubeSat detection
  95. GRB 260120B: Swift detection of a burst
  96. Swift GRB260120B: Global MASTER-Net observations report
  97. EP260119A: Mondy I-Band Observations
  98. GRB 260114A: Swift/UVOT Upper Limits
  99. Trigger 1442421: Swift detection of HMXB 1A 1118-61
  100. EP260119a: KAIT optical observations

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