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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"

27355 results found.

  1. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  2. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  3. GRB 260310A / AT 2026fgk: iTelescope optical observations
  4. EP260314a: COLIBRÍ optical upper limit
  5. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  6. EP260314a: Global MASTER-Net observations report
  7. EP260314a: SVOM/VT optical candidate
  8. Fermi trigger No 795185313: Global MASTER-Net observations report
  9. IceCube Alert 260315A: Global MASTER-Net observations report
  10. EP260314a: Einstein Probe detection of an X-ray transient
  11. GRB 260310A / AT2026fgk: SAO RAS optical observations
  12. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  13. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  14. Fermi GRB 260314A: Global MASTER-Net observations report
  15. Fermi GRB 260313A: Global MASTER-Net observations report
  16. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  17. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  18. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  19. GRB 260312B: AstroSat CZTI detection
  20. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  21. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  22. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  23. GRB 260312B: Glowbug gamma-ray detection
  24. GRB 260310A: Fermi GBM Observation
  25. GRB 260310A: potential optical counterpart
  26. Fermi GRB 260312B: Global MASTER-Net observations report
  27. Fermi GRB 260311B: Global MASTER-Net observations report
  28. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  29. GRB 260131A/B: radio detection with the VLA
  30. EP260302a: MeerKAT radio counterpart
  31. GRB 260308A: SVOM/GRM observation of a short GRB
  32. EP260306a: Mondy optical upper limit
  33. Fermi GRB 260310B: Global MASTER-Net observations report
  34. Fermi GRB 260310A: Global MASTER-Net observations report
  35. GRB 260208A: radio detection with the VLA
  36. GRB 260307A: Glowbug gamma-ray detection
  37. Fermi GBM Sub-Threshold Detection of GRB 260307B
  38. GRB 260307B: Mephisto optical upper limits
  39. GRB 260307B: possible NOT optical counterpart
  40. GRB 260307B: SVOM/VT upper limit with X band data analysis
  41. Fermi GRB 260307A: Global MASTER-Net observations report
  42. GRB260307B: GROWTH-India Telescope optical upper limit
  43. GRB 260307B: SVOM/VT optical candidate
  44. GRB 260307B: SVOM/C-GFT upper limit
  45. GRB 260307B: SVOM detection of a burst
  46. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  47. GRB 260207A: TESS Detection and Possible VLA Counterpart
  48. EP260302a: SVOM/VT optical observation
  49. EP260306a: Gemini-North redshift z = 4.773
  50. EP260306a: SVOM/VT optical observation
  51. EP260302a: Gemini-South redshift z = 1.535
  52. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  53. EP260306a: Einstein Probe detection of an X-ray transient
  54. EP260302a: Optical afterglow rebrightening
  55. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  56. GRB 260303A: 1.3m DFOT optical upper limit
  57. Fermi GRB 260305A: Global MASTER-Net observations report
  58. GRB 260303B: AstroSat CZTI detection
  59. GRB 260303A: SVOM/VT optical observations
  60. GRB 260303A: J-band observations with WINTER
  61. GRB 260303B: NuSTAR detection of prompt emission
  62. EP260302a: Global MASTER-Net observations report
  63. Fermi GRB 260303B: Global MASTER-Net observations report
  64. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  65. EP260302a: analysis of the follow-up EP-FXT observation
  66. EP260302a: LCO observations
  67. EP260302a: BOOTES-7 optical counterpart detection at early times
  68. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  69. GRB 260303A: SVOM detection of a burst
  70. GRB 260228A: EP-FXT follow-up observation
  71. EP260302a: Einstein Probe detection of an X-ray transient
  72. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  73. GRB 251130B: TERI Gamma-ray detection
  74. GRB 260208A: TERI Gamma-ray detection
  75. EP260227a: Mondy optical observations
  76. GRB 260228A: CAHA 2.2m telescope optical upper limit
  77. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  78. EP260227a: Mephisto optical detection
  79. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  80. EP260227a: SVOM/VT optical observation
  81. GRB 260228A: SVOM/VT optical upper limits
  82. GRB 260225D: SVOM/GRM observation
  83. EP260227A: 3.6m DOT optical afterglow detection
  84. GRB 260225B: SVOM/GRM observation
  85. EP260227a: Liverpool Telescope optical observations
  86. EP260227a: LCOGT Optical Observations
  87. GRB 260226A: Asiago r-band upper limit
  88. EP260227a: Liverpool Telescope observations
  89. EP260227a: COLIBRÍ optical observations
  90. EP260227a: NOT optical observations
  91. EP260227a: Global MASTER-Net observations report
  92. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  93. The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
  94. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  95. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  96. EP260214a: VLT/FORS2 optical observations
  97. GRB 260225A: WINTER J-band upper limit
  98. GRB 260226A: COLIBRÍ optical upper limits
  99. GRB 260226A: LCOGT Optical Upper Limit
  100. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare

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