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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"

35433 results found.

  1. Fermi GRB 260318A: Global MASTER-Net observations report
  2. GRB 260318A: Fermi GBM Final Real-time Localization
  3. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  4. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  5. GRB 260310A / AT 2026fgk: radio detection with the VLA
  6. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  7. GRB 260310A / AT2026fgk: LCO optical observations
  8. GRB 260317A: Fermi GBM Final Localization
  9. GRB 260316B: GECAM-B observation
  10. GRB 260316B: SVOM/GRM observation
  11. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  12. GRB 260316B: AstroSat CZTI detection
  13. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  14. GRB 260316B: Fermi GBM Final Real-time Localization
  15. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  16. GRB 260314A: Glowbug gamma-ray detection
  17. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  18. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  19. GRB 260310A / AT 2026fgk: iTelescope optical observations
  20. GRID detection of GRB 260312B
  21. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  22. GRB 260314A: GECAM-B observation of a burst
  23. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  24. GRB 260310A / AT2026fgk: SAO RAS optical observations
  25. GRB 260310A/AT2026fgk: radio detection at 15GHz
  26. GRB 260310A / AT2026fgk: TNG NIR detection
  27. GRB 260310A / AT2026fgk: OASDG optical observations
  28. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  29. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  30. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  31. Fermi GRB 260314A: Global MASTER-Net observations report
  32. Fermi GRB 260313A: Global MASTER-Net observations report
  33. GRB 260314A: Fermi GBM Final Real-time Localization
  34. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  35. GRB 260313A: A Correction to the Fermi GBM Final Localization
  36. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  37. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  38. GRB 260310B: Insight-HXMT/HE detection
  39. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  40. GRB 260310A: NOT optical polarimetry
  41. GRB 260312B: AstroSat CZTI detection
  42. Swift BAT trigger 1500295: A solar flare
  43. GRB 260313A: Fermi GBM Final Real-time Localization
  44. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  45. Swift BAT trigger 1500287: A solar flare
  46. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  47. GRB 260308A: Insight-HXMT/HE detection
  48. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  49. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  50. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  51. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  52. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  53. GRB260310A / AT2026fgk: P200 Spectroscopy
  54. GRB 260312B: Glowbug gamma-ray detection
  55. GRB 260310A: Fermi GBM Observation
  56. GRB 260310A: potential optical counterpart
  57. Fermi GRB 260312B: Global MASTER-Net observations report
  58. Fermi GRB 260311B: Global MASTER-Net observations report
  59. Swift BAT trigger 1500148: A solar flare
  60. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  61. GRB 260312B: Fermi GBM Final Real-time Localization
  62. GRB 260310B: GECAM-B observation of a burst
  63. Retraction of GCN 43965: GRB is actually solar flare
  64. GRB 260312A: Swift detection of a burst
  65. GRB 260311B: Fermi GBM Final Real-time Localization
  66. GRB 260131A/B: radio detection with the VLA
  67. GRB260307A: GECAM-B observation of a burst
  68. GRB 260308A: SVOM/GRM observation of a short GRB
  69. EP260306a: Mondy optical upper limit
  70. GRB 260310A: AstroSat CZTI detection of a long burst
  71. GRB 260311A: Fermi GBM Final Real-time Localization
  72. Fermi GRB 260310B: Global MASTER-Net observations report
  73. GRB 260310B: Fermi GBM Final Real-time Localization
  74. Fermi GRB 260310A: Global MASTER-Net observations report
  75. GRB 260307B: SVOM/ECLAIRs refined analysis
  76. GRB 260208A: radio detection with the VLA
  77. GRB 260310A: Fermi GBM Final Real-time Localization
  78. GRB 260307A: Glowbug gamma-ray detection
  79. GRB 260308A: Fermi GBM Final Real-time Localization
  80. Fermi GBM Sub-Threshold Detection of GRB 260307B
  81. GRB 260307B: Mephisto optical upper limits
  82. GRB 260307B: possible NOT optical counterpart
  83. GRB 260307B: SVOM/VT upper limit with X band data analysis
  84. Fermi GRB 260307A: Global MASTER-Net observations report
  85. GRB 260307B: SVOM/VT optical candidate
  86. GRB 260307B: SVOM/C-GFT upper limit
  87. GRB 260307B: SVOM detection of a burst
  88. GRB 260307A: Fermi GBM Final Localization
  89. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  90. GRB 260207A: TESS Detection and Possible VLA Counterpart
  91. EP260302a: Optical afterglow rebrightening
  92. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  93. GRB 260303A: 1.3m DFOT optical upper limit (duplicate submission)
  94. GRB 260303A: 1.3m DFOT optical upper limit
  95. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  96. GRB 260303A: SVOM/ECLAIRs refined analysis
  97. Fermi GRB 260305A: Global MASTER-Net observations report
  98. GRB 260305A: Fermi GBM Final Real-time Localization
  99. GRB 260303B: AstroSat CZTI detection
  100. GRB 260304A: AstroSat CZTI detection of a long burst

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