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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"

25892 results found.

  1. GRB 260511B: NOT optical observations
  2. GRB 260509A: SVOM/VT optical observations
  3. GRB 260511B: further J-band observations by the SYSU 80 cm infrared telescope
  4. GRB 260511B: FRAM-ORM optical detection
  5. GRB 260511B: LCO optical counterpart detection
  6. GRB 260511A: SVOM/VT optical observations
  7. GRB 260511B: SVOM/VT optical observations
  8. GRB 260511B: OSIRIS+/GTC redshift z=2.006
  9. GRB 260511B : MITSuME Akeno optical afterglow candidate detection
  10. GRB 260511A: UTGO H50 optical afterglow observation
  11. GRB 260511A: KAIT optical afterglow observations
  12. GRB 260511A: LCO optical afterglow detection
  13. GRB 260509A: KAIT optical observations
  14. EP260507a: NOT optical observations
  15. EP260507a: TRT optical counterpart detection
  16. GRB 260504B: SVOM/MXT refined analysis and potential detection
  17. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  18. GRB 260429B / EP260429a: EP-FXT follow-up observation
  19. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  20. GRB 260421B: Kilonova-Catcher optical afterglow detection
  21. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  22. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  23. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  24. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  25. GRB 260310A: Late-time Chandra X-ray Detection
  26. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  27. GRB 260421B: BOOTES-7 early optical afterglow detection
  28. GRB 260421B: LCO optical afterglow confirmation
  29. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  30. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  31. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  32. EP260416a: Ondrejov D50 optical detection
  33. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  34. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  35. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  36. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  37. GRB 260411B: COLIBRÍ optical observations
  38. GRB 260411B: Ondrejov D50 optical afterglow detection
  39. GRB 260411B: SVOM/GRM observation of a long burst
  40. EP260321a: Chandra X-ray Non-detection
  41. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  42. GRB 260310A / AT2026fgk: X-ray rebrightening
  43. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  44. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  45. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  46. GRB 260321A: SVOM/ECLAIRs refined analysis
  47. GRB 260310A: VLA Multi-frequency Radio Observations
  48. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  49. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  50. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  51. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  52. GRB 260310A / AT 2026fgk: KAIT optical observations
  53. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  54. GRB 260310A / AT 2026fgk: iTelescope optical observations
  55. GRB 260310A/AT2026fgk: radio detection at 15GHz
  56. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  57. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  58. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  59. Swift BAT trigger 1500295: A solar flare
  60. Swift BAT trigger 1500287: A solar flare
  61. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  62. GRB260310A / AT2026fgk: P200 Spectroscopy
  63. Swift BAT trigger 1500148: A solar flare
  64. Retraction of GCN 43965: GRB is actually solar flare
  65. GRB 260312A: Swift detection of a burst
  66. GRB 260208A: radio detection with the VLA
  67. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  68. EP260302a: Optical afterglow rebrightening
  69. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  70. GRB 260303A: SVOM/VT optical observations
  71. EP260227A: 3.6m DOT optical afterglow detection
  72. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  73. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  74. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  75. IPN triangulation of GRB 260212A
  76. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  77. Swift Operations Update + Community Forum (Friday, February 13 @ 10:00 AM EST)
  78. GRB 260208A: Swift UVOT detection
  79. GRB 260208A: LCO detection of the optical counterpart
  80. GRB 260208B: refined analysis of the EP-FXT observation
  81. GRB 260204A: Swift-XRT afterglow detection
  82. GRB 260208A: Fermi GBM Observation
  83. GRB 260208B: Swift-XRT observations
  84. GRB 260204A: Swift/UVOT Upper Limits
  85. GRB 260208A: 1.3m DFOT optical detection
  86. GRB 260208B: EP-FXT observation
  87. GRB 260208B: SVOM/VT optical candidate
  88. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  89. GRB 260208A: SVOM/VT optical observation
  90. GRB 260208A: Swift-XRT observations
  91. GRB 260208B: Swift ToO observations
  92. GRB 260208B: Fermi-LAT detection
  93. GRB 260208A: Fermi-LAT detection
  94. GRB 260208A: Swift ToO observations
  95. GRB 260208A: Fermi GBM Classification Correction
  96. GRB 260206A: Swift-XRT observations
  97. EP260131a: VLA detection
  98. GRB 260206A: Tiled Swift observations
  99. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  100. GRB 260204A: Swift-XRT observations

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