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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"
  1. GRB 260317A: Fermi GBM Final Localization
  2. GRB 260316B: GECAM-B observation
  3. GRB 260316B: SVOM/GRM observation
  4. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  5. EP260316a: COLIBRÍ faint optical counterpart candidate
  6. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  7. GRB 260316B: AstroSat CZTI detection
  8. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  9. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  10. EP260316a: Xinglong optical upper limit
  11. GRB 260316B: Fermi GBM Final Real-time Localization
  12. EP260316a: optical upper limit with Kinder observations
  13. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  14. GRB 260314A: Glowbug gamma-ray detection
  15. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  16. IceCube-260315A: COLIBRÍ optical observations
  17. EP260314a: Xinglong optical upper limit
  18. EP260314a: optical upper limit with Kinder observations
  19. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  20. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  21. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  22. GRB 260310A / AT 2026fgk: iTelescope optical observations
  23. EP260314a: COLIBRÍ optical upper limit
  24. GRID detection of GRB 260312B
  25. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  26. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  27. EP260314a: BOOTES-6/DPR optical upper limits at early times
  28. EP260314a: Global MASTER-Net observations report
  29. EP260314a: SVOM/VT optical candidate
  30. Fermi trigger No 795185313: Global MASTER-Net observations report
  31. IceCube Alert 260315A: Global MASTER-Net observations report
  32. EP260314a: Einstein Probe detection of an X-ray transient
  33. The EP-WXT trigger 01709258851: Las Cumbres upper limit
  34. GRB 260314A: GECAM-B observation of a burst
  35. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  36. GRB 260310A / AT2026fgk: SAO RAS optical observations
  37. GRB 260310A/AT2026fgk: radio detection at 15GHz
  38. GRB 260310A / AT2026fgk: TNG NIR detection
  39. GRB 260310A / AT2026fgk: OASDG optical observations
  40. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  41. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  42. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  43. Fermi GRB 260314A: Global MASTER-Net observations report
  44. Fermi GRB 260313A: Global MASTER-Net observations report
  45. GRB 260314A: Fermi GBM Final Real-time Localization
  46. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  47. GRB 260313A: A Correction to the Fermi GBM Final Localization
  48. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  49. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  50. GRB 260310B: Insight-HXMT/HE detection
  51. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  52. GRB 260310A: NOT optical polarimetry
  53. GRB 260312B: AstroSat CZTI detection
  54. Swift BAT trigger 1500295: A solar flare
  55. GRB 260313A: Fermi GBM Final Real-time Localization
  56. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  57. Swift BAT trigger 1500287: A solar flare
  58. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  59. GRB 260308A: Insight-HXMT/HE detection
  60. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  61. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  62. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  63. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  64. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  65. GRB260310A / AT2026fgk: P200 Spectroscopy
  66. GRB 260312B: Glowbug gamma-ray detection
  67. GRB 260310A: Fermi GBM Observation
  68. GRB 260310A: potential optical counterpart
  69. Fermi GRB 260312B: Global MASTER-Net observations report
  70. Fermi GRB 260311B: Global MASTER-Net observations report
  71. Swift BAT trigger 1500148: A solar flare
  72. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  73. GRB 260312B: Fermi GBM Final Real-time Localization
  74. The EP-WXT trigger 01709258843 is not a real source
  75. GRB 260310B: GECAM-B observation of a burst
  76. Retraction of GCN 43965: GRB is actually solar flare
  77. GRB 260312A: Swift detection of a burst
  78. GRB 260311B: Fermi GBM Final Real-time Localization
  79. GRB 260131A/B: radio detection with the VLA
  80. EP260302a: MeerKAT radio counterpart
  81. GRB260307A: GECAM-B observation of a burst
  82. GRB 260308A: SVOM/GRM observation of a short GRB
  83. EP260306a: Mondy optical upper limit
  84. GRB 260310A: AstroSat CZTI detection of a long burst
  85. GRB 260311A: Fermi GBM Final Real-time Localization
  86. Fermi GRB 260310B: Global MASTER-Net observations report
  87. GRB 260310B: Fermi GBM Final Real-time Localization
  88. Fermi GRB 260310A: Global MASTER-Net observations report
  89. GRB 260307B: SVOM/ECLAIRs refined analysis
  90. GRB 260208A: radio detection with the VLA
  91. GRB 260310A: Fermi GBM Final Real-time Localization
  92. GRB 260307A: Glowbug gamma-ray detection
  93. GRB 260308A: Fermi GBM Final Real-time Localization
  94. Fermi GBM Sub-Threshold Detection of GRB 260307B
  95. GRB 260307B: Mephisto optical upper limits
  96. GRB 260307B: possible NOT optical counterpart
  97. GRB 260307B: SVOM/VT upper limit with X band data analysis
  98. Fermi GRB 260307A: Global MASTER-Net observations report
  99. GRB260307B: GROWTH-India Telescope optical upper limit
  100. GRB 260307B: SVOM/VT optical candidate

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