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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: WINTER J-band upper limit
  2. EP260327a: COLIBRÍ optical upper limits
  3. EP260327a: Gemini-North optical upper limits
  4. EP260324a: GROWTH-India Telescope optical observation
  5. EP260327a: Global MASTER-Net observations report
  6. EP260327a: Einstein Probe detection of an X-ray transient
  7. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  8. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  9. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  10. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  11. GRB 260326A: Fermi GBM Detection
  12. EP260321a: JinShan near-infrared observations
  13. EP260321a: Upper limits from a neutrino search with IceCube
  14. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  15. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  16. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  17. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  18. Fermi GRB 260323A: Global MASTER-Net observations report
  19. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  20. GRB 260320A: Glowbug gamma-ray detection
  21. EP260321a: COLIBRÍ further optical observations and brightening
  22. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  23. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  24. GRB 260321A: EP-FXT follow-up observation
  25. EP260321a: GOTO detection of blue variable source
  26. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  27. EP260321a: further Kinder optical observations
  28. GRB 260321A: SVOM/VT optical upper limits
  29. EP260321a: Las Cumbres upper limit
  30. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  31. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  32. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  33. EP260321a: SVOM/VT optical upper limit
  34. Fermi GBM Sub-Threshold Detection of GRB 260321A
  35. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  36. EP260321a: Global MASTER-Net observations report
  37. EP260321a: Einstein Probe detection of an X-ray transient
  38. GRB 260318A: Glowbug gamma-ray detection
  39. GRB 260310A / AT 2026fgk: KAIT optical observations
  40. GRB 260320A: NuSTAR detection of prompt emission
  41. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  42. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  43. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  44. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  45. GRB 260318A: SVOM/GRM observation
  46. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  47. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  48. Fermi GRB 260318A: Global MASTER-Net observations report
  49. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  50. GRB 260310A / AT 2026fgk: radio detection with the VLA
  51. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  52. GRB 260310A / AT2026fgk: LCO optical observations
  53. GRB 260316B: SVOM/GRM observation
  54. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  55. EP260316a: COLIBRÍ faint optical counterpart candidate
  56. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  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. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  64. IceCube-260315A: COLIBRÍ optical observations
  65. EP260314a: Xinglong optical upper limit
  66. EP260314a: optical upper limit with Kinder observations
  67. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  68. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  69. GRB 260310A / AT 2026fgk: iTelescope optical observations
  70. EP260314a: COLIBRÍ optical upper limit
  71. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  72. EP260314a: Global MASTER-Net observations report
  73. EP260314a: SVOM/VT optical candidate
  74. Fermi trigger No 795185313: Global MASTER-Net observations report
  75. IceCube Alert 260315A: Global MASTER-Net observations report
  76. EP260314a: Einstein Probe detection of an X-ray transient
  77. GRB 260310A / AT2026fgk: SAO RAS optical observations
  78. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  79. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  80. Fermi GRB 260314A: Global MASTER-Net observations report
  81. Fermi GRB 260313A: Global MASTER-Net observations report
  82. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  83. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  84. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  85. GRB 260312B: AstroSat CZTI detection
  86. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  87. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  88. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  89. GRB 260312B: Glowbug gamma-ray detection
  90. GRB 260310A: Fermi GBM Observation
  91. GRB 260310A: potential optical counterpart
  92. Fermi GRB 260312B: Global MASTER-Net observations report
  93. Fermi GRB 260311B: Global MASTER-Net observations report
  94. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  95. GRB 260131A/B: radio detection with the VLA
  96. EP260302a: MeerKAT radio counterpart
  97. GRB 260308A: SVOM/GRM observation of a short GRB
  98. EP260306a: Mondy optical upper limit
  99. Fermi GRB 260310B: Global MASTER-Net observations report
  100. Fermi GRB 260310A: Global MASTER-Net observations report

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