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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 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  2. GRB 260310A/AT2026fgk: LBT near-infrared observations
  3. NOEMA Detection of GRB 260310A / AT 2026fgk
  4. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  5. GRB 260318A: SVOM/GRM observation
  6. The EP-WXT trigger 01709258989 is likely a flaring star
  7. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  8. GRB 260318A: GECAM-B observation
  9. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  10. Fermi GRB 260318A: Global MASTER-Net observations report
  11. GRB 260318A: Fermi GBM Final Real-time Localization
  12. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  13. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  14. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  15. GRB 260310A / AT 2026fgk: radio detection with the VLA
  16. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  17. GRB 260310A / AT2026fgk: LCO optical observations
  18. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  19. GRB 260317A: Fermi GBM Final Localization
  20. GRB 260316B: GECAM-B observation
  21. GRB 260316B: SVOM/GRM observation
  22. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  23. EP260316a: COLIBRÍ faint optical counterpart candidate
  24. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  25. GRB 260316B: AstroSat CZTI detection
  26. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  27. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  28. EP260316a: Xinglong optical upper limit
  29. GRB 260316B: Fermi GBM Final Real-time Localization
  30. EP260316a: optical upper limit with Kinder observations
  31. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  32. GRB 260314A: Glowbug gamma-ray detection
  33. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  34. IceCube-260315A: COLIBRÍ optical observations
  35. EP260314a: Xinglong optical upper limit
  36. EP260314a: optical upper limit with Kinder observations
  37. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  38. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  39. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  40. GRB 260310A / AT 2026fgk: iTelescope optical observations
  41. EP260314a: COLIBRÍ optical upper limit
  42. GRID detection of GRB 260312B
  43. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  44. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  45. EP260314a: BOOTES-6/DPR optical upper limits at early times
  46. EP260314a: Global MASTER-Net observations report
  47. EP260314a: SVOM/VT optical candidate
  48. Fermi trigger No 795185313: Global MASTER-Net observations report
  49. IceCube Alert 260315A: Global MASTER-Net observations report
  50. EP260314a: Einstein Probe detection of an X-ray transient
  51. The EP-WXT trigger 01709258851: Las Cumbres upper limit
  52. GRB 260314A: GECAM-B observation of a burst
  53. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  54. GRB 260310A / AT2026fgk: SAO RAS optical observations
  55. GRB 260310A/AT2026fgk: radio detection at 15GHz
  56. GRB 260310A / AT2026fgk: TNG NIR detection
  57. GRB 260310A / AT2026fgk: OASDG optical observations
  58. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  59. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  60. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  61. Fermi GRB 260314A: Global MASTER-Net observations report
  62. Fermi GRB 260313A: Global MASTER-Net observations report
  63. GRB 260314A: Fermi GBM Final Real-time Localization
  64. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  65. GRB 260313A: A Correction to the Fermi GBM Final Localization
  66. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  67. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  68. GRB 260310B: Insight-HXMT/HE detection
  69. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  70. GRB 260310A: NOT optical polarimetry
  71. GRB 260312B: AstroSat CZTI detection
  72. Swift BAT trigger 1500295: A solar flare
  73. GRB 260313A: Fermi GBM Final Real-time Localization
  74. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  75. Swift BAT trigger 1500287: A solar flare
  76. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  77. GRB 260308A: Insight-HXMT/HE detection
  78. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  79. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  80. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  81. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  82. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  83. GRB260310A / AT2026fgk: P200 Spectroscopy
  84. GRB 260312B: Glowbug gamma-ray detection
  85. GRB 260310A: Fermi GBM Observation
  86. GRB 260310A: potential optical counterpart
  87. Fermi GRB 260312B: Global MASTER-Net observations report
  88. Fermi GRB 260311B: Global MASTER-Net observations report
  89. Swift BAT trigger 1500148: A solar flare
  90. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  91. GRB 260312B: Fermi GBM Final Real-time Localization
  92. The EP-WXT trigger 01709258843 is not a real source
  93. GRB 260310B: GECAM-B observation of a burst
  94. Retraction of GCN 43965: GRB is actually solar flare
  95. GRB 260312A: Swift detection of a burst
  96. GRB 260311B: Fermi GBM Final Real-time Localization
  97. GRB 260131A/B: radio detection with the VLA
  98. EP260302a: MeerKAT radio counterpart
  99. GRB260307A: GECAM-B observation of a burst
  100. GRB 260308A: SVOM/GRM observation of a short GRB

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