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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"

28098 results found.

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

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