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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"

28044 results found.

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

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