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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

36111 results found.

  1. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  2. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  3. IPN triangulation of GRB 260316B
  4. GRID detection of GRB 260320A
  5. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  6. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  7. GRB 260310A: LBT optical observations
  8. EP260321A: Mondy optical observations
  9. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  10. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  11. Fermi GRB 260323A: Global MASTER-Net observations report
  12. GRB 260323A: Fermi GBM Final Real-time Localization
  13. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  14. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  15. GRB 260322A: Fermi GBM Final Localization
  16. GRB 260320A: Glowbug gamma-ray detection
  17. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  18. GRB 260321A: EP-FXT follow-up observation
  19. GRB 260321A: SVOM/VT optical upper limits
  20. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  21. GRB 260320A: Insight-HXMT/HE detection
  22. GRB 260310A: continued optical observation at Mondy
  23. Fermi GBM Sub-Threshold Detection of GRB 260321A
  24. GRB 260321A: SVOM detection of a burst
  25. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  26. GRB 260318A: Glowbug gamma-ray detection
  27. GRB 260310A / AT 2026fgk: KAIT optical observations
  28. GRB 260320A: NuSTAR detection of prompt emission
  29. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  30. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  31. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  32. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  33. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  34. GRB 260310A/AT2026fgk: LBT near-infrared observations
  35. NOEMA Detection of GRB 260310A / AT 2026fgk
  36. GRB 260318A: SVOM/GRM observation
  37. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  38. GRB 260318A: GECAM-B observation
  39. Fermi GRB 260318A: Global MASTER-Net observations report
  40. GRB 260318A: Fermi GBM Final Real-time Localization
  41. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  42. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  43. GRB 260310A / AT 2026fgk: radio detection with the VLA
  44. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  45. GRB 260310A / AT2026fgk: LCO optical observations
  46. GRB 260317A: Fermi GBM Final Localization
  47. GRB 260316B: GECAM-B observation
  48. GRB 260316B: SVOM/GRM observation
  49. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  50. GRB 260316B: AstroSat CZTI detection
  51. GRB 260316B: Fermi GBM Final Real-time Localization
  52. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  53. GRB 260314A: Glowbug gamma-ray detection
  54. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  55. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  56. GRB 260310A / AT 2026fgk: iTelescope optical observations
  57. GRID detection of GRB 260312B
  58. GRB 260314A: GECAM-B observation of a burst
  59. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  60. GRB 260310A / AT2026fgk: SAO RAS optical observations
  61. GRB 260310A/AT2026fgk: radio detection at 15GHz
  62. GRB 260310A / AT2026fgk: TNG NIR detection
  63. GRB 260310A / AT2026fgk: OASDG optical observations
  64. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  65. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  66. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  67. Fermi GRB 260314A: Global MASTER-Net observations report
  68. Fermi GRB 260313A: Global MASTER-Net observations report
  69. GRB 260314A: Fermi GBM Final Real-time Localization
  70. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  71. GRB 260313A: A Correction to the Fermi GBM Final Localization
  72. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  73. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  74. GRB 260310B: Insight-HXMT/HE detection
  75. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  76. GRB 260310A: NOT optical polarimetry
  77. GRB 260312B: AstroSat CZTI detection
  78. Swift BAT trigger 1500295: A solar flare
  79. GRB 260313A: Fermi GBM Final Real-time Localization
  80. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  81. Swift BAT trigger 1500287: A solar flare
  82. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  83. GRB 260308A: Insight-HXMT/HE detection
  84. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  85. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  86. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  87. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  88. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  89. GRB260310A / AT2026fgk: P200 Spectroscopy
  90. GRB 260312B: Glowbug gamma-ray detection
  91. GRB 260310A: Fermi GBM Observation
  92. GRB 260310A: potential optical counterpart
  93. Fermi GRB 260312B: Global MASTER-Net observations report
  94. Fermi GRB 260311B: Global MASTER-Net observations report
  95. Swift BAT trigger 1500148: A solar flare
  96. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  97. GRB 260312B: Fermi GBM Final Real-time Localization
  98. GRB 260310B: GECAM-B observation of a burst
  99. Retraction of GCN 43965: GRB is actually solar flare
  100. GRB 260312A: Swift detection of a burst

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