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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"

32507 results found.

  1. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  2. EP260321a: Global MASTER-Net observations report
  3. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  4. GRB 260318A: Glowbug gamma-ray detection
  5. GRB 260310A / AT 2026fgk: KAIT optical observations
  6. GRB 260320A: NuSTAR detection of prompt emission
  7. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  8. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  9. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  10. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  11. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  12. GRB 260310A/AT2026fgk: LBT near-infrared observations
  13. NOEMA Detection of GRB 260310A / AT 2026fgk
  14. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  15. GRB 260318A: SVOM/GRM observation
  16. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  17. GRB 260318A: GECAM-B observation
  18. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  19. Fermi GRB 260318A: Global MASTER-Net observations report
  20. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  21. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  22. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  23. GRB 260310A / AT 2026fgk: radio detection with the VLA
  24. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  25. GRB 260310A / AT2026fgk: LCO optical observations
  26. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  27. GRB 260316B: GECAM-B observation
  28. GRB 260316B: SVOM/GRM observation
  29. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  30. EP260316a: COLIBRÍ faint optical counterpart candidate
  31. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  32. GRB 260316B: AstroSat CZTI detection
  33. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  34. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  35. EP260316a: Xinglong optical upper limit
  36. EP260316a: optical upper limit with Kinder observations
  37. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  38. GRB 260314A: Glowbug gamma-ray detection
  39. IceCube-260315A: COLIBRÍ optical observations
  40. EP260314a: Xinglong optical upper limit
  41. EP260314a: optical upper limit with Kinder observations
  42. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  43. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  44. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  45. GRB 260310A / AT 2026fgk: iTelescope optical observations
  46. EP260314a: COLIBRÍ optical upper limit
  47. GRID detection of GRB 260312B
  48. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  49. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  50. EP260314a: Global MASTER-Net observations report
  51. EP260314a: SVOM/VT optical candidate
  52. GRB 260314A: GECAM-B observation of a burst
  53. GRB 260310A / AT2026fgk: SAO RAS optical observations
  54. GRB 260310A/AT2026fgk: radio detection at 15GHz
  55. GRB 260310A / AT2026fgk: TNG NIR detection
  56. GRB 260310A / AT2026fgk: OASDG optical observations
  57. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  58. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  59. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  60. Fermi GRB 260314A: Global MASTER-Net observations report
  61. Fermi GRB 260313A: Global MASTER-Net observations report
  62. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  63. GRB 260313A: A Correction to the Fermi GBM Final Localization
  64. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  65. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  66. GRB 260310B: Insight-HXMT/HE detection
  67. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  68. GRB 260310A: NOT optical polarimetry
  69. GRB 260312B: AstroSat CZTI detection
  70. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  71. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  72. GRB 260308A: Insight-HXMT/HE detection
  73. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  74. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  75. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  76. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  77. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  78. GRB260310A / AT2026fgk: P200 Spectroscopy
  79. GRB 260312B: Glowbug gamma-ray detection
  80. GRB 260310A: Fermi GBM Observation
  81. GRB 260310A: potential optical counterpart
  82. Fermi GRB 260312B: Global MASTER-Net observations report
  83. Fermi GRB 260311B: Global MASTER-Net observations report
  84. GRB 260310B: GECAM-B observation of a burst
  85. Retraction of GCN 43965: GRB is actually solar flare
  86. GRB 260131A/B: radio detection with the VLA
  87. EP260302a: MeerKAT radio counterpart
  88. GRB260307A: GECAM-B observation of a burst
  89. GRB 260308A: SVOM/GRM observation of a short GRB
  90. EP260306a: Mondy optical upper limit
  91. GRB 260310A: AstroSat CZTI detection of a long burst
  92. Fermi GRB 260310B: Global MASTER-Net observations report
  93. Fermi GRB 260310A: Global MASTER-Net observations report
  94. GRB 260307B: SVOM/ECLAIRs refined analysis
  95. GRB 260208A: radio detection with the VLA
  96. GRB 260307A: Glowbug gamma-ray detection
  97. Fermi GBM Sub-Threshold Detection of GRB 260307B
  98. GRB 260307B: Mephisto optical upper limits
  99. GRB 260307B: possible NOT optical counterpart
  100. GRB 260307B: SVOM/VT upper limit with X band data analysis

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