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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"

20362 results found.

  1. EP260327a: Einstein Probe detection of an X-ray transient
  2. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  3. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  4. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  5. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  6. EP260321a: JinShan near-infrared observations
  7. EP260321a: Upper limits from a neutrino search with IceCube
  8. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  9. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  10. GRID detection of GRB 260320A
  11. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  12. EP260321a: COLIBRÍ further optical observations and brightening
  13. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  14. EP260214b: ATCA 6 GHz detection
  15. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  16. The EP-WXT trigger 01709259045 is likely a flaring star
  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. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  24. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  25. EP260321a: SVOM/VT optical upper limit
  26. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  27. EP260321a: Einstein Probe detection of an X-ray transient
  28. GRB 260310A / AT 2026fgk: KAIT optical observations
  29. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  30. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  31. GRB 260318A: SVOM/GRM observation
  32. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  33. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  34. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  35. GRB 260310A / AT 2026fgk: radio detection with the VLA
  36. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  37. GRB 260310A / AT2026fgk: LCO optical observations
  38. GRB 260316B: SVOM/GRM observation
  39. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  40. EP260316a: COLIBRÍ faint optical counterpart candidate
  41. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  42. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  43. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  44. EP260316a: Xinglong optical upper limit
  45. EP260316a: optical upper limit with Kinder observations
  46. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  47. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  48. IceCube-260315A: COLIBRÍ optical observations
  49. EP260314a: Xinglong optical upper limit
  50. EP260314a: optical upper limit with Kinder observations
  51. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  52. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  53. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  54. GRB 260310A / AT 2026fgk: iTelescope optical observations
  55. EP260314a: COLIBRÍ optical upper limit
  56. GRID detection of GRB 260312B
  57. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  58. EP260314a: SVOM/VT optical candidate
  59. EP260314a: Einstein Probe detection of an X-ray transient
  60. GRB 260310A / AT2026fgk: SAO RAS optical observations
  61. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  62. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  63. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  64. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  65. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  66. GRB 260312B: AstroSat CZTI detection
  67. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  68. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  69. GRB 260310A: potential optical counterpart
  70. Fermi GRB 260311B: Global MASTER-Net observations report
  71. GRB 260131A/B: radio detection with the VLA
  72. EP260302a: MeerKAT radio counterpart
  73. GRB 260308A: SVOM/GRM observation of a short GRB
  74. EP260306a: Mondy optical upper limit
  75. GRB 260307B: SVOM/ECLAIRs refined analysis
  76. GRB 260208A: radio detection with the VLA
  77. GRB 260307B: Mephisto optical upper limits
  78. GRB 260307B: possible NOT optical counterpart
  79. GRB 260307B: SVOM/VT upper limit with X band data analysis
  80. GRB260307B: GROWTH-India Telescope optical upper limit
  81. GRB 260307B: SVOM/VT optical candidate
  82. GRB 260307B: SVOM/C-GFT upper limit
  83. GRB 260307B: SVOM detection of a burst
  84. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  85. GRB 260207A: TESS Detection and Possible VLA Counterpart
  86. EP260302a: SVOM/VT optical observation
  87. EP260306a: SVOM/VT optical observation
  88. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  89. EP260306a: Einstein Probe detection of an X-ray transient
  90. GRB 260303A: 1.3m DFOT optical upper limit
  91. EP260214b: ATCA 6 GHz observations
  92. GRB 260303A: SVOM/ECLAIRs refined analysis
  93. GRB 260304A: AstroSat CZTI detection of a long burst
  94. GRB 260303A: SVOM/VT optical observations
  95. GRB 260303A: J-band observations with WINTER
  96. GRB 260228A: SVOM/ECLAIRs refined analysis
  97. GRB 260225A: SVOM/ECLAIRs refined analysis
  98. EP260302a: analysis of the follow-up EP-FXT observation
  99. EP260302a: LCO observations
  100. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate

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