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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"

36149 results found.

  1. Fermi GBM Sub-Threshold Detection of GRB 260321A
  2. GRB 260321A: SVOM detection of a burst
  3. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  4. GRB 260318A: Glowbug gamma-ray detection
  5. GRB 260310A / AT 2026fgk: KAIT optical observations
  6. GRB 260320A: NuSTAR detection of prompt emission
  7. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  8. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  9. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  10. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  11. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  12. GRB 260310A/AT2026fgk: LBT near-infrared observations
  13. NOEMA Detection of GRB 260310A / AT 2026fgk
  14. GRB 260318A: SVOM/GRM observation
  15. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  16. GRB 260318A: GECAM-B observation
  17. Fermi GRB 260318A: Global MASTER-Net observations report
  18. GRB 260318A: Fermi GBM Final Real-time Localization
  19. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  20. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  21. GRB 260310A / AT 2026fgk: radio detection with the VLA
  22. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  23. GRB 260310A / AT2026fgk: LCO optical observations
  24. GRB 260317A: Fermi GBM Final Localization
  25. GRB 260316B: GECAM-B observation
  26. GRB 260316B: SVOM/GRM observation
  27. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  28. GRB 260316B: AstroSat CZTI detection
  29. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  30. GRB 260316B: Fermi GBM Final Real-time Localization
  31. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  32. GRB 260314A: Glowbug gamma-ray detection
  33. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  34. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  35. GRB 260310A / AT 2026fgk: iTelescope optical observations
  36. GRID detection of GRB 260312B
  37. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  38. GRB 260314A: GECAM-B observation of a burst
  39. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  40. GRB 260310A / AT2026fgk: SAO RAS optical observations
  41. GRB 260310A/AT2026fgk: radio detection at 15GHz
  42. GRB 260310A / AT2026fgk: TNG NIR detection
  43. GRB 260310A / AT2026fgk: OASDG optical observations
  44. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  45. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  46. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  47. Fermi GRB 260314A: Global MASTER-Net observations report
  48. Fermi GRB 260313A: Global MASTER-Net observations report
  49. GRB 260314A: Fermi GBM Final Real-time Localization
  50. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  51. GRB 260313A: A Correction to the Fermi GBM Final Localization
  52. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  53. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  54. GRB 260310B: Insight-HXMT/HE detection
  55. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  56. GRB 260310A: NOT optical polarimetry
  57. GRB 260312B: AstroSat CZTI detection
  58. Swift BAT trigger 1500295: A solar flare
  59. GRB 260313A: Fermi GBM Final Real-time Localization
  60. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  61. Swift BAT trigger 1500287: A solar flare
  62. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  63. GRB 260308A: Insight-HXMT/HE detection
  64. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  65. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  66. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  67. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  68. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  69. GRB260310A / AT2026fgk: P200 Spectroscopy
  70. GRB 260312B: Glowbug gamma-ray detection
  71. GRB 260310A: Fermi GBM Observation
  72. GRB 260310A: potential optical counterpart
  73. Fermi GRB 260312B: Global MASTER-Net observations report
  74. Fermi GRB 260311B: Global MASTER-Net observations report
  75. Swift BAT trigger 1500148: A solar flare
  76. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  77. GRB 260312B: Fermi GBM Final Real-time Localization
  78. GRB 260310B: GECAM-B observation of a burst
  79. Retraction of GCN 43965: GRB is actually solar flare
  80. GRB 260312A: Swift detection of a burst
  81. GRB 260311B: Fermi GBM Final Real-time Localization
  82. GRB 260131A/B: radio detection with the VLA
  83. GRB260307A: GECAM-B observation of a burst
  84. GRB 260308A: SVOM/GRM observation of a short GRB
  85. EP260306a: Mondy optical upper limit
  86. GRB 260310A: AstroSat CZTI detection of a long burst
  87. GRB 260311A: Fermi GBM Final Real-time Localization
  88. Fermi GRB 260310B: Global MASTER-Net observations report
  89. GRB 260310B: Fermi GBM Final Real-time Localization
  90. Fermi GRB 260310A: Global MASTER-Net observations report
  91. GRB 260307B: SVOM/ECLAIRs refined analysis
  92. GRB 260208A: radio detection with the VLA
  93. GRB 260310A: Fermi GBM Final Real-time Localization
  94. GRB 260307A: Glowbug gamma-ray detection
  95. GRB 260308A: Fermi GBM Final Real-time Localization
  96. Fermi GBM Sub-Threshold Detection of GRB 260307B
  97. GRB 260307B: Mephisto optical upper limits
  98. GRB 260307B: possible NOT optical counterpart
  99. GRB 260307B: SVOM/VT upper limit with X band data analysis
  100. Fermi GRB 260307A: Global MASTER-Net observations report

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