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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"

28096 results found.

  1. EP260321a: COLIBRÍ further optical observations and brightening
  2. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  3. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  4. GRB 260321A: EP-FXT follow-up observation
  5. EP260321a: GOTO detection of blue variable source
  6. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  7. EP260321a: further Kinder optical observations
  8. GRB 260321A: SVOM/VT optical upper limits
  9. EP260321a: Las Cumbres upper limit
  10. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  11. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  12. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  13. EP260321a: SVOM/VT optical upper limit
  14. Fermi GBM Sub-Threshold Detection of GRB 260321A
  15. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  16. EP260321a: Global MASTER-Net observations report
  17. EP260321a: Einstein Probe detection of an X-ray transient
  18. GRB 260318A: Glowbug gamma-ray detection
  19. GRB 260310A / AT 2026fgk: KAIT optical observations
  20. GRB 260320A: NuSTAR detection of prompt emission
  21. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  22. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  23. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  24. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  25. GRB 260318A: SVOM/GRM observation
  26. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  27. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  28. Fermi GRB 260318A: Global MASTER-Net observations report
  29. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  30. GRB 260310A / AT 2026fgk: radio detection with the VLA
  31. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  32. GRB 260310A / AT2026fgk: LCO optical observations
  33. GRB 260316B: SVOM/GRM observation
  34. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  35. EP260316a: COLIBRÍ faint optical counterpart candidate
  36. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  37. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  38. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  39. EP260316a: Xinglong optical upper limit
  40. EP260316a: optical upper limit with Kinder observations
  41. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  42. GRB 260314A: Glowbug gamma-ray detection
  43. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  44. IceCube-260315A: COLIBRÍ optical observations
  45. EP260314a: Xinglong optical upper limit
  46. EP260314a: optical upper limit with Kinder observations
  47. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  48. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  49. GRB 260310A / AT 2026fgk: iTelescope optical observations
  50. EP260314a: COLIBRÍ optical upper limit
  51. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  52. EP260314a: Global MASTER-Net observations report
  53. EP260314a: SVOM/VT optical candidate
  54. Fermi trigger No 795185313: Global MASTER-Net observations report
  55. IceCube Alert 260315A: Global MASTER-Net observations report
  56. EP260314a: Einstein Probe detection of an X-ray transient
  57. GRB 260310A / AT2026fgk: SAO RAS optical observations
  58. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  59. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  60. Fermi GRB 260314A: Global MASTER-Net observations report
  61. Fermi GRB 260313A: Global MASTER-Net observations report
  62. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  63. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  64. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  65. GRB 260312B: AstroSat CZTI detection
  66. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  67. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  68. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  69. GRB 260312B: Glowbug gamma-ray detection
  70. GRB 260310A: Fermi GBM Observation
  71. GRB 260310A: potential optical counterpart
  72. Fermi GRB 260312B: Global MASTER-Net observations report
  73. Fermi GRB 260311B: Global MASTER-Net observations report
  74. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  75. GRB 260131A/B: radio detection with the VLA
  76. EP260302a: MeerKAT radio counterpart
  77. GRB 260308A: SVOM/GRM observation of a short GRB
  78. EP260306a: Mondy optical upper limit
  79. Fermi GRB 260310B: Global MASTER-Net observations report
  80. Fermi GRB 260310A: Global MASTER-Net observations report
  81. GRB 260208A: radio detection with the VLA
  82. GRB 260307A: Glowbug gamma-ray detection
  83. Fermi GBM Sub-Threshold Detection of GRB 260307B
  84. GRB 260307B: Mephisto optical upper limits
  85. GRB 260307B: possible NOT optical counterpart
  86. GRB 260307B: SVOM/VT upper limit with X band data analysis
  87. Fermi GRB 260307A: Global MASTER-Net observations report
  88. GRB260307B: GROWTH-India Telescope optical upper limit
  89. GRB 260307B: SVOM/VT optical candidate
  90. GRB 260307B: SVOM/C-GFT upper limit
  91. GRB 260307B: SVOM detection of a burst
  92. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  93. GRB 260207A: TESS Detection and Possible VLA Counterpart
  94. EP260302a: SVOM/VT optical observation
  95. EP260306a: Gemini-North redshift z = 4.773
  96. EP260306a: SVOM/VT optical observation
  97. EP260302a: Gemini-South redshift z = 1.535
  98. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  99. EP260306a: Einstein Probe detection of an X-ray transient
  100. EP260302a: Optical afterglow rebrightening

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