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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"

32510 results found.

  1. EP260321a: SVOM/VT optical upper limit
  2. GRB 260310A: continued optical observation at Mondy
  3. Fermi GBM Sub-Threshold Detection of GRB 260321A
  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. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  7. GRB 260318A: Glowbug gamma-ray detection
  8. GRB 260310A / AT 2026fgk: KAIT optical observations
  9. GRB 260320A: NuSTAR detection of prompt emission
  10. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  11. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  12. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  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. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  20. GRB 260318A: GECAM-B observation
  21. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  22. Fermi GRB 260318A: Global MASTER-Net observations report
  23. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  24. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  25. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  26. GRB 260310A / AT 2026fgk: radio detection with the VLA
  27. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  28. GRB 260310A / AT2026fgk: LCO optical observations
  29. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  30. GRB 260316B: GECAM-B observation
  31. GRB 260316B: SVOM/GRM observation
  32. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  33. EP260316a: COLIBRÍ faint optical counterpart candidate
  34. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  35. GRB 260316B: AstroSat CZTI detection
  36. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  37. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  38. EP260316a: Xinglong optical upper limit
  39. EP260316a: optical upper limit with Kinder observations
  40. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  41. GRB 260314A: Glowbug gamma-ray detection
  42. IceCube-260315A: COLIBRÍ optical observations
  43. EP260314a: Xinglong optical upper limit
  44. EP260314a: optical upper limit with Kinder observations
  45. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  46. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  47. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  48. GRB 260310A / AT 2026fgk: iTelescope optical observations
  49. EP260314a: COLIBRÍ optical upper limit
  50. GRID detection of GRB 260312B
  51. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  52. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  53. EP260314a: Global MASTER-Net observations report
  54. EP260314a: SVOM/VT optical candidate
  55. GRB 260314A: GECAM-B observation of a burst
  56. GRB 260310A / AT2026fgk: SAO RAS optical observations
  57. GRB 260310A/AT2026fgk: radio detection at 15GHz
  58. GRB 260310A / AT2026fgk: TNG NIR detection
  59. GRB 260310A / AT2026fgk: OASDG optical observations
  60. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  61. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  62. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  63. Fermi GRB 260314A: Global MASTER-Net observations report
  64. Fermi GRB 260313A: Global MASTER-Net observations report
  65. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  66. GRB 260313A: A Correction to the Fermi GBM Final Localization
  67. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  68. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  69. GRB 260310B: Insight-HXMT/HE detection
  70. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  71. GRB 260310A: NOT optical polarimetry
  72. GRB 260312B: AstroSat CZTI detection
  73. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  74. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  75. GRB 260308A: Insight-HXMT/HE detection
  76. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  77. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  78. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  79. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  80. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  81. GRB260310A / AT2026fgk: P200 Spectroscopy
  82. GRB 260312B: Glowbug gamma-ray detection
  83. GRB 260310A: Fermi GBM Observation
  84. GRB 260310A: potential optical counterpart
  85. Fermi GRB 260312B: Global MASTER-Net observations report
  86. Fermi GRB 260311B: Global MASTER-Net observations report
  87. GRB 260310B: GECAM-B observation of a burst
  88. Retraction of GCN 43965: GRB is actually solar flare
  89. GRB 260131A/B: radio detection with the VLA
  90. EP260302a: MeerKAT radio counterpart
  91. GRB260307A: GECAM-B observation of a burst
  92. GRB 260308A: SVOM/GRM observation of a short GRB
  93. EP260306a: Mondy optical upper limit
  94. GRB 260310A: AstroSat CZTI detection of a long burst
  95. Fermi GRB 260310B: Global MASTER-Net observations report
  96. Fermi GRB 260310A: Global MASTER-Net observations report
  97. GRB 260307B: SVOM/ECLAIRs refined analysis
  98. GRB 260208A: radio detection with the VLA
  99. GRB 260307A: Glowbug gamma-ray detection
  100. Fermi GBM Sub-Threshold Detection of GRB 260307B

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