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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"

32506 results found.

  1. EP260321a: Global MASTER-Net observations report
  2. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  3. GRB 260318A: Glowbug gamma-ray detection
  4. GRB 260310A / AT 2026fgk: KAIT optical observations
  5. GRB 260320A: NuSTAR detection of prompt emission
  6. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  7. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  8. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  9. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  10. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  11. GRB 260310A/AT2026fgk: LBT near-infrared observations
  12. NOEMA Detection of GRB 260310A / AT 2026fgk
  13. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  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. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  18. Fermi GRB 260318A: Global MASTER-Net observations report
  19. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  20. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  21. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  22. GRB 260310A / AT 2026fgk: radio detection with the VLA
  23. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  24. GRB 260310A / AT2026fgk: LCO optical observations
  25. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  26. GRB 260316B: GECAM-B observation
  27. GRB 260316B: SVOM/GRM observation
  28. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  29. EP260316a: COLIBRÍ faint optical counterpart candidate
  30. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  31. GRB 260316B: AstroSat CZTI detection
  32. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  33. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  34. EP260316a: Xinglong optical upper limit
  35. EP260316a: optical upper limit with Kinder observations
  36. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  37. GRB 260314A: Glowbug gamma-ray detection
  38. IceCube-260315A: COLIBRÍ optical observations
  39. EP260314a: Xinglong optical upper limit
  40. EP260314a: optical upper limit with Kinder observations
  41. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  42. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  43. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  44. GRB 260310A / AT 2026fgk: iTelescope optical observations
  45. EP260314a: COLIBRÍ optical upper limit
  46. GRID detection of GRB 260312B
  47. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  48. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  49. EP260314a: Global MASTER-Net observations report
  50. EP260314a: SVOM/VT optical candidate
  51. GRB 260314A: GECAM-B observation of a burst
  52. GRB 260310A / AT2026fgk: SAO RAS optical observations
  53. GRB 260310A/AT2026fgk: radio detection at 15GHz
  54. GRB 260310A / AT2026fgk: TNG NIR detection
  55. GRB 260310A / AT2026fgk: OASDG optical observations
  56. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  57. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  58. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  59. Fermi GRB 260314A: Global MASTER-Net observations report
  60. Fermi GRB 260313A: Global MASTER-Net observations report
  61. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  62. GRB 260313A: A Correction to the Fermi GBM Final Localization
  63. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  64. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  65. GRB 260310B: Insight-HXMT/HE detection
  66. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  67. GRB 260310A: NOT optical polarimetry
  68. GRB 260312B: AstroSat CZTI detection
  69. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  70. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  71. GRB 260308A: Insight-HXMT/HE detection
  72. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  73. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  74. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  75. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  76. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  77. GRB260310A / AT2026fgk: P200 Spectroscopy
  78. GRB 260312B: Glowbug gamma-ray detection
  79. GRB 260310A: Fermi GBM Observation
  80. GRB 260310A: potential optical counterpart
  81. Fermi GRB 260312B: Global MASTER-Net observations report
  82. Fermi GRB 260311B: Global MASTER-Net observations report
  83. GRB 260310B: GECAM-B observation of a burst
  84. Retraction of GCN 43965: GRB is actually solar flare
  85. GRB 260131A/B: radio detection with the VLA
  86. EP260302a: MeerKAT radio counterpart
  87. GRB260307A: GECAM-B observation of a burst
  88. GRB 260308A: SVOM/GRM observation of a short GRB
  89. EP260306a: Mondy optical upper limit
  90. GRB 260310A: AstroSat CZTI detection of a long burst
  91. Fermi GRB 260310B: Global MASTER-Net observations report
  92. Fermi GRB 260310A: Global MASTER-Net observations report
  93. GRB 260307B: SVOM/ECLAIRs refined analysis
  94. GRB 260208A: radio detection with the VLA
  95. GRB 260307A: Glowbug gamma-ray detection
  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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