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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"

43621 results found.

  1. GRB 260310A: continued optical observation at Mondy
  2. Fermi GBM Sub-Threshold Detection of GRB 260321A
  3. GRB 260321A: SVOM detection of a burst
  4. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  5. EP260321a: Global MASTER-Net observations report
  6. EP260321a: Einstein Probe detection of an X-ray transient
  7. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  8. GRB 260318A: Glowbug gamma-ray detection
  9. GRB 260310A / AT 2026fgk: KAIT optical observations
  10. GRB 260320A: NuSTAR detection of prompt emission
  11. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  12. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  13. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  14. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  15. GRB 260310A/AT2026fgk: LBT near-infrared observations
  16. NOEMA Detection of GRB 260310A / AT 2026fgk
  17. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  18. GRB 260318A: SVOM/GRM observation
  19. The EP-WXT trigger 01709258989 is likely a flaring star
  20. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  21. GRB 260318A: GECAM-B observation
  22. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  23. Fermi GRB 260318A: Global MASTER-Net observations report
  24. GRB 260318A: Fermi GBM Final Real-time Localization
  25. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  26. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  27. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  28. GRB 260310A / AT 2026fgk: radio detection with the VLA
  29. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  30. GRB 260310A / AT2026fgk: LCO optical observations
  31. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  32. GRB 260317A: Fermi GBM Final Localization
  33. GRB 260316B: GECAM-B observation
  34. GRB 260316B: SVOM/GRM observation
  35. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  36. EP260316a: COLIBRÍ faint optical counterpart candidate
  37. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  38. GRB 260316B: AstroSat CZTI detection
  39. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  40. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  41. EP260316a: Xinglong optical upper limit
  42. GRB 260316B: Fermi GBM Final Real-time Localization
  43. EP260316a: optical upper limit with Kinder observations
  44. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  45. GRB 260314A: Glowbug gamma-ray detection
  46. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  47. IceCube-260315A: COLIBRÍ optical observations
  48. EP260314a: Xinglong optical upper limit
  49. EP260314a: optical upper limit with Kinder observations
  50. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  51. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  52. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  53. GRB 260310A / AT 2026fgk: iTelescope optical observations
  54. EP260314a: COLIBRÍ optical upper limit
  55. GRID detection of GRB 260312B
  56. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  57. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  58. EP260314a: BOOTES-6/DPR optical upper limits at early times
  59. EP260314a: Global MASTER-Net observations report
  60. EP260314a: SVOM/VT optical candidate
  61. Fermi trigger No 795185313: Global MASTER-Net observations report
  62. IceCube Alert 260315A: Global MASTER-Net observations report
  63. EP260314a: Einstein Probe detection of an X-ray transient
  64. The EP-WXT trigger 01709258851: Las Cumbres upper limit
  65. GRB 260314A: GECAM-B observation of a burst
  66. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  67. GRB 260310A / AT2026fgk: SAO RAS optical observations
  68. GRB 260310A/AT2026fgk: radio detection at 15GHz
  69. GRB 260310A / AT2026fgk: TNG NIR detection
  70. GRB 260310A / AT2026fgk: OASDG optical observations
  71. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  72. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  73. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  74. Fermi GRB 260314A: Global MASTER-Net observations report
  75. Fermi GRB 260313A: Global MASTER-Net observations report
  76. GRB 260314A: Fermi GBM Final Real-time Localization
  77. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  78. GRB 260313A: A Correction to the Fermi GBM Final Localization
  79. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  80. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  81. GRB 260310B: Insight-HXMT/HE detection
  82. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  83. GRB 260310A: NOT optical polarimetry
  84. GRB 260312B: AstroSat CZTI detection
  85. Swift BAT trigger 1500295: A solar flare
  86. GRB 260313A: Fermi GBM Final Real-time Localization
  87. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  88. Swift BAT trigger 1500287: A solar flare
  89. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  90. GRB 260308A: Insight-HXMT/HE detection
  91. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  92. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  93. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  94. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  95. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  96. GRB260310A / AT2026fgk: P200 Spectroscopy
  97. GRB 260312B: Glowbug gamma-ray detection
  98. GRB 260310A: Fermi GBM Observation
  99. GRB 260310A: potential optical counterpart
  100. Fermi GRB 260312B: Global MASTER-Net observations report

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