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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"

36143 results found.

  1. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  2. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  3. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  4. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  5. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  6. GRB 260310A/AT2026fgk: LBT near-infrared observations
  7. NOEMA Detection of GRB 260310A / AT 2026fgk
  8. GRB 260318A: SVOM/GRM observation
  9. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  10. GRB 260318A: GECAM-B observation
  11. Fermi GRB 260318A: Global MASTER-Net observations report
  12. GRB 260318A: Fermi GBM Final Real-time Localization
  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. GRB 260317A: Fermi GBM Final Localization
  19. GRB 260316B: GECAM-B observation
  20. GRB 260316B: SVOM/GRM observation
  21. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  22. GRB 260316B: AstroSat CZTI detection
  23. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  24. GRB 260316B: Fermi GBM Final Real-time Localization
  25. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  26. GRB 260314A: Glowbug gamma-ray detection
  27. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  28. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  29. GRB 260310A / AT 2026fgk: iTelescope optical observations
  30. GRID detection of GRB 260312B
  31. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  32. GRB 260314A: GECAM-B observation of a burst
  33. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  34. GRB 260310A / AT2026fgk: SAO RAS optical observations
  35. GRB 260310A/AT2026fgk: radio detection at 15GHz
  36. GRB 260310A / AT2026fgk: TNG NIR detection
  37. GRB 260310A / AT2026fgk: OASDG optical observations
  38. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  39. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  40. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  41. Fermi GRB 260314A: Global MASTER-Net observations report
  42. Fermi GRB 260313A: Global MASTER-Net observations report
  43. GRB 260314A: Fermi GBM Final Real-time Localization
  44. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  45. GRB 260313A: A Correction to the Fermi GBM Final Localization
  46. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  47. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  48. GRB 260310B: Insight-HXMT/HE detection
  49. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  50. GRB 260310A: NOT optical polarimetry
  51. GRB 260312B: AstroSat CZTI detection
  52. Swift BAT trigger 1500295: A solar flare
  53. GRB 260313A: Fermi GBM Final Real-time Localization
  54. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  55. Swift BAT trigger 1500287: A solar flare
  56. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  57. GRB 260308A: Insight-HXMT/HE detection
  58. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  59. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  60. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  61. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  62. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  63. GRB260310A / AT2026fgk: P200 Spectroscopy
  64. GRB 260312B: Glowbug gamma-ray detection
  65. GRB 260310A: Fermi GBM Observation
  66. GRB 260310A: potential optical counterpart
  67. Fermi GRB 260312B: Global MASTER-Net observations report
  68. Fermi GRB 260311B: Global MASTER-Net observations report
  69. Swift BAT trigger 1500148: A solar flare
  70. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  71. GRB 260312B: Fermi GBM Final Real-time Localization
  72. GRB 260310B: GECAM-B observation of a burst
  73. Retraction of GCN 43965: GRB is actually solar flare
  74. GRB 260312A: Swift detection of a burst
  75. GRB 260311B: Fermi GBM Final Real-time Localization
  76. GRB 260131A/B: radio detection with the VLA
  77. GRB260307A: GECAM-B observation of a burst
  78. GRB 260308A: SVOM/GRM observation of a short GRB
  79. EP260306a: Mondy optical upper limit
  80. GRB 260310A: AstroSat CZTI detection of a long burst
  81. GRB 260311A: Fermi GBM Final Real-time Localization
  82. Fermi GRB 260310B: Global MASTER-Net observations report
  83. GRB 260310B: Fermi GBM Final Real-time Localization
  84. Fermi GRB 260310A: Global MASTER-Net observations report
  85. GRB 260307B: SVOM/ECLAIRs refined analysis
  86. GRB 260208A: radio detection with the VLA
  87. GRB 260310A: Fermi GBM Final Real-time Localization
  88. GRB 260307A: Glowbug gamma-ray detection
  89. GRB 260308A: Fermi GBM Final Real-time Localization
  90. Fermi GBM Sub-Threshold Detection of GRB 260307B
  91. GRB 260307B: Mephisto optical upper limits
  92. GRB 260307B: possible NOT optical counterpart
  93. GRB 260307B: SVOM/VT upper limit with X band data analysis
  94. Fermi GRB 260307A: Global MASTER-Net observations report
  95. GRB 260307B: SVOM/VT optical candidate
  96. GRB 260307B: SVOM/C-GFT upper limit
  97. GRB 260307B: SVOM detection of a burst
  98. GRB 260307A: Fermi GBM Final Localization
  99. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  100. GRB 260207A: TESS Detection and Possible VLA Counterpart

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