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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 260318A: SVOM/GRM observation
  2. The EP-WXT trigger 01709258989 is likely a flaring star
  3. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  4. GRB 260318A: GECAM-B observation
  5. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  6. Fermi GRB 260318A: Global MASTER-Net observations report
  7. GRB 260318A: Fermi GBM Final Real-time Localization
  8. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  9. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  10. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  11. GRB 260310A / AT 2026fgk: radio detection with the VLA
  12. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  13. GRB 260310A / AT2026fgk: LCO optical observations
  14. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  15. GRB 260317A: Fermi GBM Final Localization
  16. GRB 260316B: GECAM-B observation
  17. GRB 260316B: SVOM/GRM observation
  18. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  19. EP260316a: COLIBRÍ faint optical counterpart candidate
  20. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  21. GRB 260316B: AstroSat CZTI detection
  22. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  23. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  24. EP260316a: Xinglong optical upper limit
  25. GRB 260316B: Fermi GBM Final Real-time Localization
  26. EP260316a: optical upper limit with Kinder observations
  27. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  28. GRB 260314A: Glowbug gamma-ray detection
  29. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  30. IceCube-260315A: COLIBRÍ optical observations
  31. EP260314a: Xinglong optical upper limit
  32. EP260314a: optical upper limit with Kinder observations
  33. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  34. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  35. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  36. GRB 260310A / AT 2026fgk: iTelescope optical observations
  37. EP260314a: COLIBRÍ optical upper limit
  38. GRID detection of GRB 260312B
  39. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  40. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  41. EP260314a: BOOTES-6/DPR optical upper limits at early times
  42. EP260314a: Global MASTER-Net observations report
  43. EP260314a: SVOM/VT optical candidate
  44. Fermi trigger No 795185313: Global MASTER-Net observations report
  45. IceCube Alert 260315A: Global MASTER-Net observations report
  46. EP260314a: Einstein Probe detection of an X-ray transient
  47. The EP-WXT trigger 01709258851: Las Cumbres upper limit
  48. GRB 260314A: GECAM-B observation of a burst
  49. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  50. GRB 260310A / AT2026fgk: SAO RAS optical observations
  51. GRB 260310A/AT2026fgk: radio detection at 15GHz
  52. GRB 260310A / AT2026fgk: TNG NIR detection
  53. GRB 260310A / AT2026fgk: OASDG optical observations
  54. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  55. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  56. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  57. Fermi GRB 260314A: Global MASTER-Net observations report
  58. Fermi GRB 260313A: Global MASTER-Net observations report
  59. GRB 260314A: Fermi GBM Final Real-time Localization
  60. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  61. GRB 260313A: A Correction to the Fermi GBM Final Localization
  62. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  63. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  64. GRB 260310B: Insight-HXMT/HE detection
  65. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  66. GRB 260310A: NOT optical polarimetry
  67. GRB 260312B: AstroSat CZTI detection
  68. Swift BAT trigger 1500295: A solar flare
  69. GRB 260313A: Fermi GBM Final Real-time Localization
  70. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  71. Swift BAT trigger 1500287: A solar flare
  72. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  73. GRB 260308A: Insight-HXMT/HE detection
  74. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  75. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  76. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  77. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  78. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  79. GRB260310A / AT2026fgk: P200 Spectroscopy
  80. GRB 260312B: Glowbug gamma-ray detection
  81. GRB 260310A: Fermi GBM Observation
  82. GRB 260310A: potential optical counterpart
  83. Fermi GRB 260312B: Global MASTER-Net observations report
  84. Fermi GRB 260311B: Global MASTER-Net observations report
  85. Swift BAT trigger 1500148: A solar flare
  86. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  87. GRB 260312B: Fermi GBM Final Real-time Localization
  88. The EP-WXT trigger 01709258843 is not a real source
  89. GRB 260310B: GECAM-B observation of a burst
  90. Retraction of GCN 43965: GRB is actually solar flare
  91. GRB 260312A: Swift detection of a burst
  92. GRB 260311B: Fermi GBM Final Real-time Localization
  93. GRB 260131A/B: radio detection with the VLA
  94. EP260302a: MeerKAT radio counterpart
  95. GRB260307A: GECAM-B observation of a burst
  96. GRB 260308A: SVOM/GRM observation of a short GRB
  97. EP260306a: Mondy optical upper limit
  98. GRB 260310A: AstroSat CZTI detection of a long burst
  99. GRB 260311A: Fermi GBM Final Real-time Localization
  100. Fermi GRB 260310B: Global MASTER-Net observations report

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