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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"

31727 results found.

  1. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  2. GRB 260320A: Glowbug gamma-ray detection
  3. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  4. EP260321a: COLIBRÍ further optical observations and brightening
  5. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  6. EP260214b: ATCA 6 GHz detection
  7. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  8. GRB 260321A: EP-FXT follow-up observation
  9. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  10. EP260321a: GOTO detection of blue variable source
  11. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  12. EP260321a: further Kinder optical observations
  13. GRB 260321A: SVOM/VT optical upper limits
  14. EP260321a: Las Cumbres upper limit
  15. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  16. GRB 260320A: Insight-HXMT/HE detection
  17. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  18. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  19. EP260321a: SVOM/VT optical upper limit
  20. GRB 260310A: continued optical observation at Mondy
  21. Fermi GBM Sub-Threshold Detection of GRB 260321A
  22. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  23. EP260321a: Global MASTER-Net observations report
  24. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  25. GRB 260318A: Glowbug gamma-ray detection
  26. GRB 260310A / AT 2026fgk: KAIT optical observations
  27. GRB 260320A: NuSTAR detection of prompt emission
  28. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  29. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  30. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  31. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  32. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  33. GRB 260310A/AT2026fgk: LBT near-infrared observations
  34. NOEMA Detection of GRB 260310A / AT 2026fgk
  35. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  36. GRB 260318A: SVOM/GRM observation
  37. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  38. GRB 260318A: GECAM-B observation
  39. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  40. Fermi GRB 260318A: Global MASTER-Net observations report
  41. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  42. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  43. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  44. GRB 260310A / AT 2026fgk: radio detection with the VLA
  45. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  46. GRB 260310A / AT2026fgk: LCO optical observations
  47. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  48. GRB 260316B: GECAM-B observation
  49. GRB 260316B: SVOM/GRM observation
  50. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  51. EP260316a: COLIBRÍ faint optical counterpart candidate
  52. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  53. GRB 260316B: AstroSat CZTI detection
  54. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  55. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  56. EP260316a: Xinglong optical upper limit
  57. EP260316a: optical upper limit with Kinder observations
  58. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  59. GRB 260314A: Glowbug gamma-ray detection
  60. IceCube-260315A: COLIBRÍ optical observations
  61. EP260314a: Xinglong optical upper limit
  62. EP260314a: optical upper limit with Kinder observations
  63. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  64. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  65. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  66. GRB 260310A / AT 2026fgk: iTelescope optical observations
  67. EP260314a: COLIBRÍ optical upper limit
  68. GRID detection of GRB 260312B
  69. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  70. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  71. EP260314a: Global MASTER-Net observations report
  72. EP260314a: SVOM/VT optical candidate
  73. GRB 260314A: GECAM-B observation of a burst
  74. GRB 260310A / AT2026fgk: SAO RAS optical observations
  75. GRB 260310A/AT2026fgk: radio detection at 15GHz
  76. GRB 260310A / AT2026fgk: TNG NIR detection
  77. GRB 260310A / AT2026fgk: OASDG optical observations
  78. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  79. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  80. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  81. Fermi GRB 260314A: Global MASTER-Net observations report
  82. Fermi GRB 260313A: Global MASTER-Net observations report
  83. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  84. GRB 260313A: A Correction to the Fermi GBM Final Localization
  85. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  86. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  87. GRB 260310B: Insight-HXMT/HE detection
  88. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  89. GRB 260310A: NOT optical polarimetry
  90. GRB 260312B: AstroSat CZTI detection
  91. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  92. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  93. GRB 260308A: Insight-HXMT/HE detection
  94. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  95. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  96. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  97. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  98. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  99. GRB260310A / AT2026fgk: P200 Spectroscopy
  100. GRB 260312B: Glowbug gamma-ray detection

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