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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"

15245 results found.

  1. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  2. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  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. EP260321a: GOTO detection of blue variable source
  7. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  8. EP260321a: further Kinder optical observations
  9. GRB 260320A: Insight-HXMT/HE detection
  10. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  11. EP260321a: SVOM/VT optical upper limit
  12. GRB 260321A: SVOM detection of a burst
  13. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  14. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  15. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  16. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  17. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  18. GRB 260318A: SVOM/GRM observation
  19. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  20. GRB 260318A: GECAM-B observation
  21. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  22. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  23. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  24. GRB 260310A / AT2026fgk: LCO optical observations
  25. GRB 260316B: GECAM-B observation
  26. GRB 260316B: SVOM/GRM observation
  27. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  28. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  29. GRB 260316B: AstroSat CZTI detection
  30. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  31. EP260316a: optical upper limit with Kinder observations
  32. GRB 260314A: Glowbug gamma-ray detection
  33. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  34. IceCube-260315A: COLIBRÍ optical observations
  35. EP260314a: optical upper limit with Kinder observations
  36. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  37. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  38. EP260314a: COLIBRÍ optical upper limit
  39. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  40. EP260314a: BOOTES-6/DPR optical upper limits at early times
  41. GRB 260314A: GECAM-B observation of a burst
  42. GRB 260310A/AT2026fgk: radio detection at 15GHz
  43. GRB 260310A / AT2026fgk: TNG NIR detection
  44. GRB 260310A / AT2026fgk: OASDG optical observations
  45. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  46. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  47. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  48. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  49. GRB 260313A: A Correction to the Fermi GBM Final Localization
  50. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  51. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  52. GRB 260310B: Insight-HXMT/HE detection
  53. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  54. GRB 260312B: AstroSat CZTI detection
  55. GRB 260308A: Insight-HXMT/HE detection
  56. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  57. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  58. GRB260310A / AT2026fgk: P200 Spectroscopy
  59. GRB 260310A: Fermi GBM Observation
  60. GRB 260310B: GECAM-B observation of a burst
  61. Retraction of GCN 43965: GRB is actually solar flare
  62. GRB 260312A: Swift detection of a burst
  63. GRB260307A: GECAM-B observation of a burst
  64. GRB 260308A: SVOM/GRM observation of a short GRB
  65. EP260306a: Mondy optical upper limit
  66. GRB 260310A: AstroSat CZTI detection of a long burst
  67. GRB 260307B: SVOM/ECLAIRs refined analysis
  68. GRB 260307B: Mephisto optical upper limits
  69. GRB 260307B: possible NOT optical counterpart
  70. GRB 260307B: SVOM/VT upper limit with X band data analysis
  71. GRB 260307B: SVOM detection of a burst
  72. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  73. GRB 260207A: TESS Detection and Possible VLA Counterpart
  74. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  75. EP260306a: Einstein Probe detection of an X-ray transient
  76. GRB 260303A: 1.3m DFOT optical upper limit
  77. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  78. GRB 260303A: SVOM/ECLAIRs refined analysis
  79. GRB 260303B: AstroSat CZTI detection
  80. GRB 260304A: AstroSat CZTI detection of a long burst
  81. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  82. GRB 260303A: SVOM/VT optical observations
  83. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  84. GRB 260228A: SVOM/ECLAIRs refined analysis
  85. GRB 260225A: SVOM/ECLAIRs refined analysis
  86. EP260302a: LCO observations
  87. EP260302a: BOOTES-7 optical counterpart detection at early times
  88. GRB 260303A: SVOM detection of a burst
  89. GRB 251130B: TERI Gamma-ray detection
  90. GRB 260208A: TERI Gamma-ray detection
  91. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  92. EP260227a: Mephisto optical detection
  93. GRID detection of GRB 260225D
  94. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  95. GRB 260225D: SVOM/GRM observation
  96. GRB 260225B: SVOM/GRM observation
  97. GRB 260228A: SVOM detection of a burst
  98. EP260227a: Liverpool Telescope optical observations
  99. EP260227a: COLIBRÍ optical observations
  100. EP260227a: NOT optical observations

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