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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"

31737 results found.

  1. EP260321a: Gemini-South confirmation of a supernova (duplicate submission)
  2. EP260321a: Gemini-South confirmation of a supernova
  3. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  4. GRB 260310A: LBT optical observations
  5. EP260321A: Mondy optical observations
  6. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  7. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  8. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  9. Fermi GRB 260323A: Global MASTER-Net observations report
  10. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  11. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  12. GRB 260320A: Glowbug gamma-ray detection
  13. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  14. EP260321a: COLIBRÍ further optical observations and brightening
  15. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  16. EP260214b: ATCA 6 GHz detection
  17. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  18. GRB 260321A: EP-FXT follow-up observation
  19. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  20. EP260321a: GOTO detection of blue variable source
  21. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  22. EP260321a: further Kinder optical observations
  23. GRB 260321A: SVOM/VT optical upper limits
  24. EP260321a: Las Cumbres upper limit
  25. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  26. GRB 260320A: Insight-HXMT/HE detection
  27. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  28. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  29. EP260321a: SVOM/VT optical upper limit
  30. GRB 260310A: continued optical observation at Mondy
  31. Fermi GBM Sub-Threshold Detection of GRB 260321A
  32. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  33. EP260321a: Global MASTER-Net observations report
  34. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  35. GRB 260318A: Glowbug gamma-ray detection
  36. GRB 260310A / AT 2026fgk: KAIT optical observations
  37. GRB 260320A: NuSTAR detection of prompt emission
  38. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  39. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  40. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  41. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  42. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  43. GRB 260310A/AT2026fgk: LBT near-infrared observations
  44. NOEMA Detection of GRB 260310A / AT 2026fgk
  45. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  46. GRB 260318A: SVOM/GRM observation
  47. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  48. GRB 260318A: GECAM-B observation
  49. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  50. Fermi GRB 260318A: Global MASTER-Net observations report
  51. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  52. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  53. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  54. GRB 260310A / AT 2026fgk: radio detection with the VLA
  55. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  56. GRB 260310A / AT2026fgk: LCO optical observations
  57. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  58. GRB 260316B: GECAM-B observation
  59. GRB 260316B: SVOM/GRM observation
  60. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  61. EP260316a: COLIBRÍ faint optical counterpart candidate
  62. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  63. GRB 260316B: AstroSat CZTI detection
  64. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  65. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  66. EP260316a: Xinglong optical upper limit
  67. EP260316a: optical upper limit with Kinder observations
  68. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  69. GRB 260314A: Glowbug gamma-ray detection
  70. IceCube-260315A: COLIBRÍ optical observations
  71. EP260314a: Xinglong optical upper limit
  72. EP260314a: optical upper limit with Kinder observations
  73. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  74. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  75. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  76. GRB 260310A / AT 2026fgk: iTelescope optical observations
  77. EP260314a: COLIBRÍ optical upper limit
  78. GRID detection of GRB 260312B
  79. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  80. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  81. EP260314a: Global MASTER-Net observations report
  82. EP260314a: SVOM/VT optical candidate
  83. GRB 260314A: GECAM-B observation of a burst
  84. GRB 260310A / AT2026fgk: SAO RAS optical observations
  85. GRB 260310A/AT2026fgk: radio detection at 15GHz
  86. GRB 260310A / AT2026fgk: TNG NIR detection
  87. GRB 260310A / AT2026fgk: OASDG optical observations
  88. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  89. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  90. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  91. Fermi GRB 260314A: Global MASTER-Net observations report
  92. Fermi GRB 260313A: Global MASTER-Net observations report
  93. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  94. GRB 260313A: A Correction to the Fermi GBM Final Localization
  95. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  96. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  97. GRB 260310B: Insight-HXMT/HE detection
  98. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  99. GRB 260310A: NOT optical polarimetry
  100. GRB 260312B: AstroSat CZTI detection

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