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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"

31735 results found.

  1. GRB 260310A: LBT optical observations
  2. EP260321A: Mondy optical observations
  3. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  4. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  5. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  6. Fermi GRB 260323A: Global MASTER-Net observations report
  7. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  8. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  9. GRB 260320A: Glowbug gamma-ray detection
  10. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  11. EP260321a: COLIBRÍ further optical observations and brightening
  12. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  13. EP260214b: ATCA 6 GHz detection
  14. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  15. GRB 260321A: EP-FXT follow-up observation
  16. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  17. EP260321a: GOTO detection of blue variable source
  18. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  19. EP260321a: further Kinder optical observations
  20. GRB 260321A: SVOM/VT optical upper limits
  21. EP260321a: Las Cumbres upper limit
  22. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  23. GRB 260320A: Insight-HXMT/HE detection
  24. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  25. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  26. EP260321a: SVOM/VT optical upper limit
  27. GRB 260310A: continued optical observation at Mondy
  28. Fermi GBM Sub-Threshold Detection of GRB 260321A
  29. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  30. EP260321a: Global MASTER-Net observations report
  31. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  32. GRB 260318A: Glowbug gamma-ray detection
  33. GRB 260310A / AT 2026fgk: KAIT optical observations
  34. GRB 260320A: NuSTAR detection of prompt emission
  35. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  36. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  37. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  38. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  39. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  40. GRB 260310A/AT2026fgk: LBT near-infrared observations
  41. NOEMA Detection of GRB 260310A / AT 2026fgk
  42. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  43. GRB 260318A: SVOM/GRM observation
  44. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  45. GRB 260318A: GECAM-B observation
  46. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  47. Fermi GRB 260318A: Global MASTER-Net observations report
  48. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  49. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  50. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  51. GRB 260310A / AT 2026fgk: radio detection with the VLA
  52. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  53. GRB 260310A / AT2026fgk: LCO optical observations
  54. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  55. GRB 260316B: GECAM-B observation
  56. GRB 260316B: SVOM/GRM observation
  57. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  58. EP260316a: COLIBRÍ faint optical counterpart candidate
  59. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  60. GRB 260316B: AstroSat CZTI detection
  61. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  62. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  63. EP260316a: Xinglong optical upper limit
  64. EP260316a: optical upper limit with Kinder observations
  65. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  66. GRB 260314A: Glowbug gamma-ray detection
  67. IceCube-260315A: COLIBRÍ optical observations
  68. EP260314a: Xinglong optical upper limit
  69. EP260314a: optical upper limit with Kinder observations
  70. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  71. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  72. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  73. GRB 260310A / AT 2026fgk: iTelescope optical observations
  74. EP260314a: COLIBRÍ optical upper limit
  75. GRID detection of GRB 260312B
  76. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  77. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  78. EP260314a: Global MASTER-Net observations report
  79. EP260314a: SVOM/VT optical candidate
  80. GRB 260314A: GECAM-B observation of a burst
  81. GRB 260310A / AT2026fgk: SAO RAS optical observations
  82. GRB 260310A/AT2026fgk: radio detection at 15GHz
  83. GRB 260310A / AT2026fgk: TNG NIR detection
  84. GRB 260310A / AT2026fgk: OASDG optical observations
  85. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  86. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  87. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  88. Fermi GRB 260314A: Global MASTER-Net observations report
  89. Fermi GRB 260313A: Global MASTER-Net observations report
  90. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  91. GRB 260313A: A Correction to the Fermi GBM Final Localization
  92. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  93. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  94. GRB 260310B: Insight-HXMT/HE detection
  95. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  96. GRB 260310A: NOT optical polarimetry
  97. GRB 260312B: AstroSat CZTI detection
  98. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  99. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  100. GRB 260308A: Insight-HXMT/HE detection

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