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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"

31730 results found.

  1. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  2. Fermi GRB 260323A: Global MASTER-Net observations report
  3. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  4. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  5. GRB 260320A: Glowbug gamma-ray detection
  6. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  7. EP260321a: COLIBRÍ further optical observations and brightening
  8. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  9. EP260214b: ATCA 6 GHz detection
  10. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  11. GRB 260321A: EP-FXT follow-up observation
  12. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  13. EP260321a: GOTO detection of blue variable source
  14. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  15. EP260321a: further Kinder optical observations
  16. GRB 260321A: SVOM/VT optical upper limits
  17. EP260321a: Las Cumbres upper limit
  18. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  19. GRB 260320A: Insight-HXMT/HE detection
  20. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  21. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  22. EP260321a: SVOM/VT optical upper limit
  23. GRB 260310A: continued optical observation at Mondy
  24. Fermi GBM Sub-Threshold Detection of GRB 260321A
  25. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  26. EP260321a: Global MASTER-Net observations report
  27. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  28. GRB 260318A: Glowbug gamma-ray detection
  29. GRB 260310A / AT 2026fgk: KAIT optical observations
  30. GRB 260320A: NuSTAR detection of prompt emission
  31. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  32. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  33. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  34. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  35. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  36. GRB 260310A/AT2026fgk: LBT near-infrared observations
  37. NOEMA Detection of GRB 260310A / AT 2026fgk
  38. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  39. GRB 260318A: SVOM/GRM observation
  40. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  41. GRB 260318A: GECAM-B observation
  42. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  43. Fermi GRB 260318A: Global MASTER-Net observations report
  44. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  45. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  46. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  47. GRB 260310A / AT 2026fgk: radio detection with the VLA
  48. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  49. GRB 260310A / AT2026fgk: LCO optical observations
  50. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  51. GRB 260316B: GECAM-B observation
  52. GRB 260316B: SVOM/GRM observation
  53. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  54. EP260316a: COLIBRÍ faint optical counterpart candidate
  55. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  56. GRB 260316B: AstroSat CZTI detection
  57. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  58. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  59. EP260316a: Xinglong optical upper limit
  60. EP260316a: optical upper limit with Kinder observations
  61. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  62. GRB 260314A: Glowbug gamma-ray detection
  63. IceCube-260315A: COLIBRÍ optical observations
  64. EP260314a: Xinglong optical upper limit
  65. EP260314a: optical upper limit with Kinder observations
  66. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  67. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  68. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  69. GRB 260310A / AT 2026fgk: iTelescope optical observations
  70. EP260314a: COLIBRÍ optical upper limit
  71. GRID detection of GRB 260312B
  72. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  73. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  74. EP260314a: Global MASTER-Net observations report
  75. EP260314a: SVOM/VT optical candidate
  76. GRB 260314A: GECAM-B observation of a burst
  77. GRB 260310A / AT2026fgk: SAO RAS optical observations
  78. GRB 260310A/AT2026fgk: radio detection at 15GHz
  79. GRB 260310A / AT2026fgk: TNG NIR detection
  80. GRB 260310A / AT2026fgk: OASDG optical observations
  81. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  82. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  83. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  84. Fermi GRB 260314A: Global MASTER-Net observations report
  85. Fermi GRB 260313A: Global MASTER-Net observations report
  86. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  87. GRB 260313A: A Correction to the Fermi GBM Final Localization
  88. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  89. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  90. GRB 260310B: Insight-HXMT/HE detection
  91. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  92. GRB 260310A: NOT optical polarimetry
  93. GRB 260312B: AstroSat CZTI detection
  94. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  95. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  96. GRB 260308A: Insight-HXMT/HE detection
  97. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  98. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  99. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  100. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations

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