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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"

32509 results found.

  1. GRB 260310A: continued optical observation at Mondy
  2. Fermi GBM Sub-Threshold Detection of GRB 260321A
  3. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  4. EP260321a: Global MASTER-Net observations report
  5. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  6. GRB 260318A: Glowbug gamma-ray detection
  7. GRB 260310A / AT 2026fgk: KAIT optical observations
  8. GRB 260320A: NuSTAR detection of prompt emission
  9. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  10. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  11. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  12. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  13. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  14. GRB 260310A/AT2026fgk: LBT near-infrared observations
  15. NOEMA Detection of GRB 260310A / AT 2026fgk
  16. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  17. GRB 260318A: SVOM/GRM observation
  18. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  19. GRB 260318A: GECAM-B observation
  20. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  21. Fermi GRB 260318A: Global MASTER-Net observations report
  22. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  23. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  24. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  25. GRB 260310A / AT 2026fgk: radio detection with the VLA
  26. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  27. GRB 260310A / AT2026fgk: LCO optical observations
  28. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  29. GRB 260316B: GECAM-B observation
  30. GRB 260316B: SVOM/GRM observation
  31. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  32. EP260316a: COLIBRÍ faint optical counterpart candidate
  33. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  34. GRB 260316B: AstroSat CZTI detection
  35. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  36. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  37. EP260316a: Xinglong optical upper limit
  38. EP260316a: optical upper limit with Kinder observations
  39. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  40. GRB 260314A: Glowbug gamma-ray detection
  41. IceCube-260315A: COLIBRÍ optical observations
  42. EP260314a: Xinglong optical upper limit
  43. EP260314a: optical upper limit with Kinder observations
  44. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  45. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  46. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  47. GRB 260310A / AT 2026fgk: iTelescope optical observations
  48. EP260314a: COLIBRÍ optical upper limit
  49. GRID detection of GRB 260312B
  50. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  51. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  52. EP260314a: Global MASTER-Net observations report
  53. EP260314a: SVOM/VT optical candidate
  54. GRB 260314A: GECAM-B observation of a burst
  55. GRB 260310A / AT2026fgk: SAO RAS optical observations
  56. GRB 260310A/AT2026fgk: radio detection at 15GHz
  57. GRB 260310A / AT2026fgk: TNG NIR detection
  58. GRB 260310A / AT2026fgk: OASDG optical observations
  59. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  60. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  61. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  62. Fermi GRB 260314A: Global MASTER-Net observations report
  63. Fermi GRB 260313A: Global MASTER-Net observations report
  64. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  65. GRB 260313A: A Correction to the Fermi GBM Final Localization
  66. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  67. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  68. GRB 260310B: Insight-HXMT/HE detection
  69. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  70. GRB 260310A: NOT optical polarimetry
  71. GRB 260312B: AstroSat CZTI detection
  72. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  73. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  74. GRB 260308A: Insight-HXMT/HE detection
  75. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  76. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  77. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  78. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  79. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  80. GRB260310A / AT2026fgk: P200 Spectroscopy
  81. GRB 260312B: Glowbug gamma-ray detection
  82. GRB 260310A: Fermi GBM Observation
  83. GRB 260310A: potential optical counterpart
  84. Fermi GRB 260312B: Global MASTER-Net observations report
  85. Fermi GRB 260311B: Global MASTER-Net observations report
  86. GRB 260310B: GECAM-B observation of a burst
  87. Retraction of GCN 43965: GRB is actually solar flare
  88. GRB 260131A/B: radio detection with the VLA
  89. EP260302a: MeerKAT radio counterpart
  90. GRB260307A: GECAM-B observation of a burst
  91. GRB 260308A: SVOM/GRM observation of a short GRB
  92. EP260306a: Mondy optical upper limit
  93. GRB 260310A: AstroSat CZTI detection of a long burst
  94. Fermi GRB 260310B: Global MASTER-Net observations report
  95. Fermi GRB 260310A: Global MASTER-Net observations report
  96. GRB 260307B: SVOM/ECLAIRs refined analysis
  97. GRB 260208A: radio detection with the VLA
  98. GRB 260307A: Glowbug gamma-ray detection
  99. Fermi GBM Sub-Threshold Detection of GRB 260307B
  100. GRB 260307B: Mephisto optical upper limits

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