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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"

36206 results found.

  1. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  2. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  3. IPN triangulation of GRB 260320A
  4. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  5. GRB 260326A: Fermi GBM Detection
  6. GRB 260325A: Fermi GBM Final Localization
  7. GRB 260326A: Fermi GBM Final Real-time Localization
  8. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  9. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  10. IPN triangulation of GRB 260316B
  11. GRID detection of GRB 260320A
  12. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  13. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  14. GRB 260310A: LBT optical observations
  15. EP260321A: Mondy optical observations
  16. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  17. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  18. Fermi GRB 260323A: Global MASTER-Net observations report
  19. GRB 260323A: Fermi GBM Final Real-time Localization
  20. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  21. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  22. GRB 260322A: Fermi GBM Final Localization
  23. GRB 260320A: Glowbug gamma-ray detection
  24. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  25. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  26. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  27. GRB 260321A: EP-FXT follow-up observation
  28. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  29. GRB 260321A: SVOM/VT optical upper limits
  30. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  31. GRB 260320A: Insight-HXMT/HE detection
  32. GRB 260310A: continued optical observation at Mondy
  33. Fermi GBM Sub-Threshold Detection of GRB 260321A
  34. GRB 260321A: SVOM detection of a burst
  35. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  36. GRB 260318A: Glowbug gamma-ray detection
  37. GRB 260310A / AT 2026fgk: KAIT optical observations
  38. GRB 260320A: NuSTAR detection of prompt emission
  39. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  40. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  41. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  42. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  43. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  44. GRB 260310A/AT2026fgk: LBT near-infrared observations
  45. NOEMA Detection of GRB 260310A / AT 2026fgk
  46. GRB 260318A: SVOM/GRM observation
  47. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  48. GRB 260318A: GECAM-B observation
  49. Fermi GRB 260318A: Global MASTER-Net observations report
  50. GRB 260318A: Fermi GBM Final Real-time Localization
  51. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  52. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  53. GRB 260310A / AT 2026fgk: radio detection with the VLA
  54. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  55. GRB 260310A / AT2026fgk: LCO optical observations
  56. GRB 260317A: Fermi GBM Final Localization
  57. GRB 260316B: GECAM-B observation
  58. GRB 260316B: SVOM/GRM observation
  59. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  60. GRB 260316B: AstroSat CZTI detection
  61. GRB 260316B: Fermi GBM Final Real-time Localization
  62. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  63. GRB 260314A: Glowbug gamma-ray detection
  64. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  65. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  66. GRB 260310A / AT 2026fgk: iTelescope optical observations
  67. GRID detection of GRB 260312B
  68. GRB 260314A: GECAM-B observation of a burst
  69. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  70. GRB 260310A / AT2026fgk: SAO RAS optical observations
  71. GRB 260310A/AT2026fgk: radio detection at 15GHz
  72. GRB 260310A / AT2026fgk: TNG NIR detection
  73. GRB 260310A / AT2026fgk: OASDG optical observations
  74. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  75. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  76. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  77. Fermi GRB 260314A: Global MASTER-Net observations report
  78. Fermi GRB 260313A: Global MASTER-Net observations report
  79. GRB 260314A: Fermi GBM Final Real-time Localization
  80. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  81. GRB 260313A: A Correction to the Fermi GBM Final Localization
  82. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  83. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  84. GRB 260310B: Insight-HXMT/HE detection
  85. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  86. GRB 260310A: NOT optical polarimetry
  87. GRB 260312B: AstroSat CZTI detection
  88. Swift BAT trigger 1500295: A solar flare
  89. GRB 260313A: Fermi GBM Final Real-time Localization
  90. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  91. Swift BAT trigger 1500287: A solar flare
  92. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  93. GRB 260308A: Insight-HXMT/HE detection
  94. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  95. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  96. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  97. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  98. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  99. GRB260310A / AT2026fgk: P200 Spectroscopy
  100. GRB 260312B: Glowbug gamma-ray detection

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