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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"

27369 results found.

  1. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  2. Fermi GRB 260318A: Global MASTER-Net observations report
  3. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  4. GRB 260310A / AT 2026fgk: radio detection with the VLA
  5. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  6. GRB 260310A / AT2026fgk: LCO optical observations
  7. GRB 260316B: SVOM/GRM observation
  8. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  9. EP260316a: COLIBRÍ faint optical counterpart candidate
  10. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  11. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  12. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  13. EP260316a: Xinglong optical upper limit
  14. EP260316a: optical upper limit with Kinder observations
  15. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  16. GRB 260314A: Glowbug gamma-ray detection
  17. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  18. IceCube-260315A: COLIBRÍ optical observations
  19. EP260314a: Xinglong optical upper limit
  20. EP260314a: optical upper limit with Kinder observations
  21. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  22. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  23. GRB 260310A / AT 2026fgk: iTelescope optical observations
  24. EP260314a: COLIBRÍ optical upper limit
  25. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  26. EP260314a: Global MASTER-Net observations report
  27. EP260314a: SVOM/VT optical candidate
  28. Fermi trigger No 795185313: Global MASTER-Net observations report
  29. IceCube Alert 260315A: Global MASTER-Net observations report
  30. EP260314a: Einstein Probe detection of an X-ray transient
  31. GRB 260310A / AT2026fgk: SAO RAS optical observations
  32. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  33. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  34. Fermi GRB 260314A: Global MASTER-Net observations report
  35. Fermi GRB 260313A: Global MASTER-Net observations report
  36. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  37. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  38. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  39. GRB 260312B: AstroSat CZTI detection
  40. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  41. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  42. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  43. GRB 260312B: Glowbug gamma-ray detection
  44. GRB 260310A: Fermi GBM Observation
  45. GRB 260310A: potential optical counterpart
  46. Fermi GRB 260312B: Global MASTER-Net observations report
  47. Fermi GRB 260311B: Global MASTER-Net observations report
  48. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  49. GRB 260131A/B: radio detection with the VLA
  50. EP260302a: MeerKAT radio counterpart
  51. GRB 260308A: SVOM/GRM observation of a short GRB
  52. EP260306a: Mondy optical upper limit
  53. Fermi GRB 260310B: Global MASTER-Net observations report
  54. Fermi GRB 260310A: Global MASTER-Net observations report
  55. GRB 260208A: radio detection with the VLA
  56. GRB 260307A: Glowbug gamma-ray detection
  57. Fermi GBM Sub-Threshold Detection of GRB 260307B
  58. GRB 260307B: Mephisto optical upper limits
  59. GRB 260307B: possible NOT optical counterpart
  60. GRB 260307B: SVOM/VT upper limit with X band data analysis
  61. Fermi GRB 260307A: Global MASTER-Net observations report
  62. GRB260307B: GROWTH-India Telescope optical upper limit
  63. GRB 260307B: SVOM/VT optical candidate
  64. GRB 260307B: SVOM/C-GFT upper limit
  65. GRB 260307B: SVOM detection of a burst
  66. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  67. GRB 260207A: TESS Detection and Possible VLA Counterpart
  68. EP260302a: SVOM/VT optical observation
  69. EP260306a: Gemini-North redshift z = 4.773
  70. EP260306a: SVOM/VT optical observation
  71. EP260302a: Gemini-South redshift z = 1.535
  72. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  73. EP260306a: Einstein Probe detection of an X-ray transient
  74. EP260302a: Optical afterglow rebrightening
  75. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  76. GRB 260303A: 1.3m DFOT optical upper limit
  77. Fermi GRB 260305A: Global MASTER-Net observations report
  78. GRB 260303B: AstroSat CZTI detection
  79. GRB 260303A: SVOM/VT optical observations
  80. GRB 260303A: J-band observations with WINTER
  81. GRB 260303B: NuSTAR detection of prompt emission
  82. EP260302a: Global MASTER-Net observations report
  83. Fermi GRB 260303B: Global MASTER-Net observations report
  84. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  85. EP260302a: analysis of the follow-up EP-FXT observation
  86. EP260302a: LCO observations
  87. EP260302a: BOOTES-7 optical counterpart detection at early times
  88. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  89. GRB 260303A: SVOM detection of a burst
  90. GRB 260228A: EP-FXT follow-up observation
  91. EP260302a: Einstein Probe detection of an X-ray transient
  92. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  93. GRB 251130B: TERI Gamma-ray detection
  94. GRB 260208A: TERI Gamma-ray detection
  95. EP260227a: Mondy optical observations
  96. GRB 260228A: CAHA 2.2m telescope optical upper limit
  97. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  98. EP260227a: Mephisto optical detection
  99. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  100. EP260227a: SVOM/VT optical observation

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