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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

28115 results found.

  1. EP260327a: COLIBRÍ optical upper limits
  2. EP260327a: Gemini-North optical upper limits
  3. EP260324a: GROWTH-India Telescope optical observation
  4. EP260327a: Global MASTER-Net observations report
  5. EP260327a: Einstein Probe detection of an X-ray transient
  6. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  7. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  8. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  9. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  10. GRB 260326A: Fermi GBM Detection
  11. EP260321a: JinShan near-infrared observations
  12. EP260321a: Upper limits from a neutrino search with IceCube
  13. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  14. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  15. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  16. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  17. Fermi GRB 260323A: Global MASTER-Net observations report
  18. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  19. GRB 260320A: Glowbug gamma-ray detection
  20. EP260321a: COLIBRÍ further optical observations and brightening
  21. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  22. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  23. GRB 260321A: EP-FXT follow-up observation
  24. EP260321a: GOTO detection of blue variable source
  25. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  26. EP260321a: further Kinder optical observations
  27. GRB 260321A: SVOM/VT optical upper limits
  28. EP260321a: Las Cumbres upper limit
  29. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  30. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  31. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  32. EP260321a: SVOM/VT optical upper limit
  33. Fermi GBM Sub-Threshold Detection of GRB 260321A
  34. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  35. EP260321a: Global MASTER-Net observations report
  36. EP260321a: Einstein Probe detection of an X-ray transient
  37. GRB 260318A: Glowbug gamma-ray detection
  38. GRB 260310A / AT 2026fgk: KAIT optical observations
  39. GRB 260320A: NuSTAR detection of prompt emission
  40. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  41. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  42. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  43. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  44. GRB 260318A: SVOM/GRM observation
  45. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  46. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  47. Fermi GRB 260318A: Global MASTER-Net observations report
  48. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  49. GRB 260310A / AT 2026fgk: radio detection with the VLA
  50. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  51. GRB 260310A / AT2026fgk: LCO optical observations
  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. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  57. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  58. EP260316a: Xinglong optical upper limit
  59. EP260316a: optical upper limit with Kinder observations
  60. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  61. GRB 260314A: Glowbug gamma-ray detection
  62. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  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 / AT 2026fgk: iTelescope optical observations
  69. EP260314a: COLIBRÍ optical upper limit
  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. Fermi trigger No 795185313: Global MASTER-Net observations report
  74. IceCube Alert 260315A: Global MASTER-Net observations report
  75. EP260314a: Einstein Probe detection of an X-ray transient
  76. GRB 260310A / AT2026fgk: SAO RAS optical observations
  77. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  78. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  79. Fermi GRB 260314A: Global MASTER-Net observations report
  80. Fermi GRB 260313A: Global MASTER-Net observations report
  81. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  82. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  83. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  84. GRB 260312B: AstroSat CZTI detection
  85. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  86. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  87. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  88. GRB 260312B: Glowbug gamma-ray detection
  89. GRB 260310A: Fermi GBM Observation
  90. GRB 260310A: potential optical counterpart
  91. Fermi GRB 260312B: Global MASTER-Net observations report
  92. Fermi GRB 260311B: Global MASTER-Net observations report
  93. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  94. GRB 260131A/B: radio detection with the VLA
  95. EP260302a: MeerKAT radio counterpart
  96. GRB 260308A: SVOM/GRM observation of a short GRB
  97. EP260306a: Mondy optical upper limit
  98. Fermi GRB 260310B: Global MASTER-Net observations report
  99. Fermi GRB 260310A: Global MASTER-Net observations report
  100. GRB 260208A: radio detection with the VLA

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