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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"

14803 results found.

  1. GRB 260310A / AT2026fgk: X-ray rebrightening
  2. EP260402a / GRB 260402A: Mephisto optical upper limits
  3. EP260403a: Mephisto optical upper limits
  4. GRID detection of GRB 260401A
  5. GRB 260403A: GECAM-B observation of a long burst
  6. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  7. GRB 260330B: SVOM/ECLAIRs refined analysis
  8. EP260403a: LCO optical observations of the counterpart
  9. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  10. EP260403a: LCO optical counterpart detection
  11. GRB 260403A: AstroSat CZTI detection
  12. GRB 260402B: GECAM-B observation
  13. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  14. GRB 260402C: AstroSat CZTI detection of a long burst
  15. EP260324A / AT 2026hir: COLIBRÍ optical observations
  16. GRB 260402A: WINTER J-band upper limit
  17. GRB260402A: GROWTH-India Telescope optical upper limit
  18. GRB 260401A: SVOM/GRM observation
  19. GRB 260401A: GECAM-B observation
  20. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  21. GRB 260402A: SVOM detection of a burst
  22. GRB 260401A: Fermi GBM Observation
  23. EP260329b: Mondy and Assy-Turgen optical upper limits
  24. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  25. EP260329b: GOTO detection of optical counterpart
  26. Konus-Wind detection of GRB 260320A
  27. Konus-Wind detection of GRB 260316B
  28. GRB 260321A: SVOM/ECLAIRs refined analysis
  29. GRB 260310A: VLA Multi-frequency Radio Observations
  30. GRB 260330B: SVOM detection of a burst
  31. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  32. EP260329a: COLIBRÍ optical upper limit
  33. EP260329a: EP-FXT follow up observation
  34. GRB 260327A: Insight-HXMT/HE detection
  35. EP260329b: Optical follow-up with Kinder observations
  36. EP 260329b: COLIBRÍ optical observations
  37. EP260329a: Optical upper limit with Kinder observations
  38. EP260329b: LCO optical observations of the counterpart
  39. GRB 260326A: Insight-HXMT/HE detection
  40. EP260329b: Einstein Probe detection of an X-ray transient
  41. EP-WXT trigger 01709259209: TRT optical counterpart detection
  42. GRID detection of GRB 260326A
  43. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  44. GRB 260327A: AstroSat CZTI detection of a long burst
  45. EP260324a: GROWTH-India Telescope optical observation
  46. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  47. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  48. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  49. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  50. GRB 260326A: Fermi GBM Detection
  51. EP260321a: Upper limits from a neutrino search with IceCube
  52. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  53. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  54. GRID detection of GRB 260320A
  55. GRB 260310A: LBT optical observations
  56. EP260321A: Mondy optical observations
  57. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  58. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  59. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  60. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  61. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  62. EP260321a: COLIBRÍ further optical observations and brightening
  63. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  64. EP260321a: GOTO detection of blue variable source
  65. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  66. EP260321a: further Kinder optical observations
  67. GRB 260320A: Insight-HXMT/HE detection
  68. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  69. EP260321a: SVOM/VT optical upper limit
  70. GRB 260321A: SVOM detection of a burst
  71. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  72. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  73. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  74. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  75. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  76. GRB 260318A: SVOM/GRM observation
  77. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  78. GRB 260318A: GECAM-B observation
  79. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  80. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  81. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  82. GRB 260310A / AT2026fgk: LCO optical observations
  83. GRB 260316B: GECAM-B observation
  84. GRB 260316B: SVOM/GRM observation
  85. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  86. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  87. GRB 260316B: AstroSat CZTI detection
  88. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  89. EP260316a: optical upper limit with Kinder observations
  90. GRB 260314A: Glowbug gamma-ray detection
  91. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  92. IceCube-260315A: COLIBRÍ optical observations
  93. EP260314a: optical upper limit with Kinder observations
  94. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  95. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  96. EP260314a: COLIBRÍ optical upper limit
  97. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  98. EP260314a: BOOTES-6/DPR optical upper limits at early times
  99. GRB 260314A: GECAM-B observation of a burst
  100. GRB 260310A/AT2026fgk: radio detection at 15GHz

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