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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. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  2. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  3. EP260314a: BOOTES-6/DPR optical upper limits at early times
  4. EP260314a: Global MASTER-Net observations report
  5. EP260314a: SVOM/VT optical candidate
  6. Fermi trigger No 795185313: Global MASTER-Net observations report
  7. IceCube Alert 260315A: Global MASTER-Net observations report
  8. EP260314a: Einstein Probe detection of an X-ray transient
  9. The EP-WXT trigger 01709258851: Las Cumbres upper limit
  10. GRB 260314A: GECAM-B observation of a burst
  11. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  12. GRB 260310A / AT2026fgk: SAO RAS optical observations
  13. GRB 260310A/AT2026fgk: radio detection at 15GHz
  14. GRB 260310A / AT2026fgk: TNG NIR detection
  15. GRB 260310A / AT2026fgk: OASDG optical observations
  16. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  17. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  18. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  19. Fermi GRB 260314A: Global MASTER-Net observations report
  20. Fermi GRB 260313A: Global MASTER-Net observations report
  21. GRB 260314A: Fermi GBM Final Real-time Localization
  22. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  23. GRB 260313A: A Correction to the Fermi GBM Final Localization
  24. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  25. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  26. GRB 260310B: Insight-HXMT/HE detection
  27. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  28. GRB 260310A: NOT optical polarimetry
  29. GRB 260312B: AstroSat CZTI detection
  30. Swift BAT trigger 1500295: A solar flare
  31. GRB 260313A: Fermi GBM Final Real-time Localization
  32. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  33. Swift BAT trigger 1500287: A solar flare
  34. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  35. GRB 260308A: Insight-HXMT/HE detection
  36. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  37. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  38. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  39. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  40. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  41. GRB260310A / AT2026fgk: P200 Spectroscopy
  42. GRB 260312B: Glowbug gamma-ray detection
  43. GRB 260310A: Fermi GBM Observation
  44. GRB 260310A: potential optical counterpart
  45. Fermi GRB 260312B: Global MASTER-Net observations report
  46. Fermi GRB 260311B: Global MASTER-Net observations report
  47. Swift BAT trigger 1500148: A solar flare
  48. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  49. GRB 260312B: Fermi GBM Final Real-time Localization
  50. The EP-WXT trigger 01709258843 is not a real source
  51. GRB 260310B: GECAM-B observation of a burst
  52. Retraction of GCN 43965: GRB is actually solar flare
  53. GRB 260312A: Swift detection of a burst
  54. GRB 260311B: Fermi GBM Final Real-time Localization
  55. GRB 260131A/B: radio detection with the VLA
  56. EP260302a: MeerKAT radio counterpart
  57. GRB260307A: GECAM-B observation of a burst
  58. GRB 260308A: SVOM/GRM observation of a short GRB
  59. EP260306a: Mondy optical upper limit
  60. GRB 260310A: AstroSat CZTI detection of a long burst
  61. GRB 260311A: Fermi GBM Final Real-time Localization
  62. Fermi GRB 260310B: Global MASTER-Net observations report
  63. GRB 260310B: Fermi GBM Final Real-time Localization
  64. Fermi GRB 260310A: Global MASTER-Net observations report
  65. GRB 260307B: SVOM/ECLAIRs refined analysis
  66. GRB 260208A: radio detection with the VLA
  67. GRB 260310A: Fermi GBM Final Real-time Localization
  68. GRB 260307A: Glowbug gamma-ray detection
  69. GRB 260308A: Fermi GBM Final Real-time Localization
  70. Fermi GBM Sub-Threshold Detection of GRB 260307B
  71. GRB 260307B: Mephisto optical upper limits
  72. GRB 260307B: possible NOT optical counterpart
  73. GRB 260307B: SVOM/VT upper limit with X band data analysis
  74. Fermi GRB 260307A: Global MASTER-Net observations report
  75. GRB260307B: GROWTH-India Telescope optical upper limit
  76. GRB 260307B: SVOM/VT optical candidate
  77. GRB 260307B: SVOM/C-GFT upper limit
  78. GRB 260307B: SVOM detection of a burst
  79. GRB 260307A: Fermi GBM Final Localization
  80. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  81. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  82. GRB 260207A: TESS Detection and Possible VLA Counterpart
  83. EP260302a: SVOM/VT optical observation
  84. EP260306a: Gemini-North redshift z = 4.773
  85. EP260306a: SVOM/VT optical observation
  86. EP260302a: Gemini-South redshift z = 1.535
  87. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  88. EP260306a: Einstein Probe detection of an X-ray transient
  89. The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart
  90. EP260302a: Optical afterglow rebrightening
  91. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  92. GRB 260303A: 1.3m DFOT optical upper limit (duplicate submission)
  93. GRB 260303A: 1.3m DFOT optical upper limit
  94. EP260214b: ATCA 6 GHz observations
  95. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  96. GRB 260303A: SVOM/ECLAIRs refined analysis
  97. Fermi GRB 260305A: Global MASTER-Net observations report
  98. GRB 260305A: Fermi GBM Final Real-time Localization
  99. GRB 260303B: AstroSat CZTI detection
  100. GRB 260304A: AstroSat CZTI detection of a long burst

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