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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"

25559 results found.

  1. GRB 260326A: Insight-HXMT/HE detection
  2. EP260329b: Einstein Probe detection of an X-ray transient
  3. EP260329a: Einstein Probe detection of an X-ray transient
  4. EP-WXT trigger 01709259209: TRT optical counterpart detection
  5. GRID detection of GRB 260326A
  6. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  7. EP260327a: SVOM/VT optical upper limits
  8. GRB 260307B: ATCA Radio Upper Limits
  9. EP260327a: WINTER J-band upper limit
  10. EP260327a: COLIBRÍ optical upper limits
  11. GRB 260327A: AstroSat CZTI detection of a long burst
  12. EP260324a: GROWTH-India Telescope optical observation
  13. EP260327a: Einstein Probe detection of an X-ray transient
  14. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  15. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  16. IPN triangulation of GRB 260320A
  17. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  18. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  19. GRB 260326A: Fermi GBM Detection
  20. EP260321a: Upper limits from a neutrino search with IceCube
  21. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  22. IPN triangulation of GRB 260316B
  23. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  24. GRID detection of GRB 260320A
  25. EP260321a: Gemini-South confirmation of a supernova
  26. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  27. GRB 260310A: LBT optical observations
  28. EP260321A: Mondy optical observations
  29. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  30. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  31. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  32. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  33. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  34. GRB 260320A: Glowbug gamma-ray detection
  35. EP260321a: COLIBRÍ further optical observations and brightening
  36. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  37. EP260214b: ATCA 6 GHz detection
  38. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  39. GRB 260321A: EP-FXT follow-up observation
  40. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  41. EP260321a: GOTO detection of blue variable source
  42. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  43. GRB 260321A: SVOM/VT optical upper limits
  44. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  45. GRB 260320A: Insight-HXMT/HE detection
  46. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  47. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  48. EP260321a: SVOM/VT optical upper limit
  49. GRB 260310A: continued optical observation at Mondy
  50. Fermi GBM Sub-Threshold Detection of GRB 260321A
  51. GRB 260321A: SVOM detection of a burst
  52. EP260321a: Einstein Probe detection of an X-ray transient
  53. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  54. GRB 260318A: Glowbug gamma-ray detection
  55. GRB 260320A: NuSTAR detection of prompt emission
  56. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  57. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  58. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  59. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  60. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  61. GRB 260310A/AT2026fgk: LBT near-infrared observations
  62. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  63. GRB 260318A: SVOM/GRM observation
  64. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  65. GRB 260318A: GECAM-B observation
  66. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  67. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  68. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  69. GRB 260310A / AT 2026fgk: radio detection with the VLA
  70. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  71. GRB 260310A / AT2026fgk: LCO optical observations
  72. GRB 260316B: GECAM-B observation
  73. GRB 260316B: SVOM/GRM observation
  74. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  75. EP260316a: COLIBRÍ faint optical counterpart candidate
  76. GRB 260316B: AstroSat CZTI detection
  77. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  78. EP260316a: Xinglong optical upper limit
  79. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  80. GRB 260314A: Glowbug gamma-ray detection
  81. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  82. IceCube-260315A: COLIBRÍ optical observations
  83. EP260314a: Xinglong optical upper limit
  84. EP260314a: optical upper limit with Kinder observations
  85. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  86. GRB 260310A / AT 2026fgk: iTelescope optical observations
  87. EP260314a: COLIBRÍ optical upper limit
  88. GRID detection of GRB 260312B
  89. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  90. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  91. EP260314a: BOOTES-6/DPR optical upper limits at early times
  92. EP260314a: SVOM/VT optical candidate
  93. EP260314a: Einstein Probe detection of an X-ray transient
  94. GRB 260314A: GECAM-B observation of a burst
  95. GRB 260310A / AT2026fgk: SAO RAS optical observations
  96. GRB 260310A / AT2026fgk: TNG NIR detection
  97. GRB 260310A / AT2026fgk: OASDG optical observations
  98. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  99. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  100. GRB 260310A/AT 2026fgk: WINTER NIR Detections

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