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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"

27348 results found.

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

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