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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"

36270 results found.

  1. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  2. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  3. GRB 260310A / AT 2026fgk: iTelescope optical observations
  4. GRID detection of GRB 260312B
  5. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  6. Fermi trigger No 795185313: Global MASTER-Net observations report
  7. GRB 260314A: GECAM-B observation of a burst
  8. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  9. GRB 260310A / AT2026fgk: SAO RAS optical observations
  10. GRB 260310A/AT2026fgk: radio detection at 15GHz
  11. GRB 260310A / AT2026fgk: TNG NIR detection
  12. GRB 260310A / AT2026fgk: OASDG optical observations
  13. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  14. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  15. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  16. Fermi GRB 260314A: Global MASTER-Net observations report
  17. Fermi GRB 260313A: Global MASTER-Net observations report
  18. GRB 260314A: Fermi GBM Final Real-time Localization
  19. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  20. GRB 260313A: A Correction to the Fermi GBM Final Localization
  21. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  22. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  23. GRB 260310B: Insight-HXMT/HE detection
  24. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  25. GRB 260310A: NOT optical polarimetry
  26. GRB 260312B: AstroSat CZTI detection
  27. Swift BAT trigger 1500295: A solar flare
  28. GRB 260313A: Fermi GBM Final Real-time Localization
  29. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  30. Swift BAT trigger 1500287: A solar flare
  31. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  32. GRB 260308A: Insight-HXMT/HE detection
  33. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  34. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  35. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  36. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  37. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  38. GRB260310A / AT2026fgk: P200 Spectroscopy
  39. GRB 260312B: Glowbug gamma-ray detection
  40. GRB 260310A: Fermi GBM Observation
  41. GRB 260310A: potential optical counterpart
  42. Fermi GRB 260312B: Global MASTER-Net observations report
  43. Fermi GRB 260311B: Global MASTER-Net observations report
  44. Swift BAT trigger 1500148: A solar flare
  45. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  46. GRB 260312B: Fermi GBM Final Real-time Localization
  47. GRB 260310B: GECAM-B observation of a burst
  48. Retraction of GCN 43965: GRB is actually solar flare
  49. GRB 260312A: Swift detection of a burst
  50. GRB 260311B: Fermi GBM Final Real-time Localization
  51. GRB 260131A/B: radio detection with the VLA
  52. GRB260307A: GECAM-B observation of a burst
  53. GRB 260308A: SVOM/GRM observation of a short GRB
  54. EP260306a: Mondy optical upper limit
  55. GRB 260310A: AstroSat CZTI detection of a long burst
  56. GRB 260311A: Fermi GBM Final Real-time Localization
  57. Fermi GRB 260310B: Global MASTER-Net observations report
  58. GRB 260310B: Fermi GBM Final Real-time Localization
  59. Fermi GRB 260310A: Global MASTER-Net observations report
  60. GRB 260307B: SVOM/ECLAIRs refined analysis
  61. GRB 260208A: radio detection with the VLA
  62. GRB 260310A: Fermi GBM Final Real-time Localization
  63. GRB 260307A: Glowbug gamma-ray detection
  64. GRB 260308A: Fermi GBM Final Real-time Localization
  65. Fermi GBM Sub-Threshold Detection of GRB 260307B
  66. GRB 260307B: Mephisto optical upper limits
  67. GRB 260307B: possible NOT optical counterpart
  68. GRB 260307B: SVOM/VT upper limit with X band data analysis
  69. Fermi GRB 260307A: Global MASTER-Net observations report
  70. GRB 260307B: SVOM/VT optical candidate
  71. GRB 260307B: SVOM/C-GFT upper limit
  72. GRB 260307B: SVOM detection of a burst
  73. GRB 260307A: Fermi GBM Final Localization
  74. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  75. GRB 260207A: TESS Detection and Possible VLA Counterpart
  76. EP260302a: Optical afterglow rebrightening
  77. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  78. GRB 260303A: 1.3m DFOT optical upper limit (duplicate submission)
  79. GRB 260303A: 1.3m DFOT optical upper limit
  80. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  81. GRB 260303A: SVOM/ECLAIRs refined analysis
  82. Fermi GRB 260305A: Global MASTER-Net observations report
  83. GRB 260305A: Fermi GBM Final Real-time Localization
  84. GRB 260303B: AstroSat CZTI detection
  85. GRB 260304A: AstroSat CZTI detection of a long burst
  86. GRB 260303A: SVOM/VT optical observations
  87. GRB 260303A: J-band observations with WINTER
  88. GRB 260303B: NuSTAR detection of prompt emission
  89. Fermi GRB 260303B: Global MASTER-Net observations report
  90. GRB 260228A: SVOM/ECLAIRs refined analysis
  91. GRB 260225A: SVOM/ECLAIRs refined analysis
  92. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  93. GRB 260303B: Fermi GBM Final Real-time Localization
  94. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  95. GRB 260303A: SVOM detection of a burst
  96. GRB 260228A: EP-FXT follow-up observation
  97. GRB 251130B: TERI Gamma-ray detection
  98. GRB 260208A: TERI Gamma-ray detection
  99. GRB 260302A: Fermi GBM Final Real-time Localization
  100. EP260227a: Mondy optical observations

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