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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"
  1. EP260327a: Global MASTER-Net observations report
  2. EP260327a: Einstein Probe detection of an X-ray transient
  3. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  4. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  5. The EP-WXT trigger 01709259173 is likely a flaring star
  6. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  7. IPN triangulation of GRB 260320A
  8. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  9. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  10. GRB 260326A: Fermi GBM Detection
  11. EP260321a: JinShan near-infrared observations
  12. GRB 260325A: Fermi GBM Final Localization
  13. GRB 260326A: Fermi GBM Final Real-time Localization
  14. EP260321a: Upper limits from a neutrino search with IceCube
  15. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  16. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  17. IPN triangulation of GRB 260316B
  18. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  19. GRID detection of GRB 260320A
  20. EP260321a: Gemini-South confirmation of a supernova (duplicate submission)
  21. EP260321a: Gemini-South confirmation of a supernova
  22. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  23. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  24. GRB 260310A: LBT optical observations
  25. EP260321A: Mondy optical observations
  26. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  27. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  28. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  29. The EP-WXT trigger 01709259112 is likely a flaring star
  30. Fermi GRB 260323A: Global MASTER-Net observations report
  31. GRB 260323A: Fermi GBM Final Real-time Localization
  32. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  33. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  34. GRB 260322A: Fermi GBM Final Localization
  35. GRB 260320A: Glowbug gamma-ray detection
  36. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  37. EP260321a: COLIBRÍ further optical observations and brightening
  38. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  39. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  40. EP260214b: ATCA 6 GHz detection
  41. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  42. GRB 260321A: EP-FXT follow-up observation
  43. The EP-WXT trigger 01709259045 is likely a flaring star
  44. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  45. EP260321a: GOTO detection of blue variable source
  46. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  47. EP260321a: further Kinder optical observations
  48. GRB 260321A: SVOM/VT optical upper limits
  49. EP260321a: Las Cumbres upper limit
  50. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  51. GRB 260320A: Insight-HXMT/HE detection
  52. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  53. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  54. EP260321a: SVOM/VT optical upper limit
  55. GRB 260310A: continued optical observation at Mondy
  56. Fermi GBM Sub-Threshold Detection of GRB 260321A
  57. GRB 260321A: SVOM detection of a burst
  58. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  59. EP260321a: Global MASTER-Net observations report
  60. EP260321a: Einstein Probe detection of an X-ray transient
  61. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  62. GRB 260318A: Glowbug gamma-ray detection
  63. GRB 260310A / AT 2026fgk: KAIT optical observations
  64. GRB 260320A: NuSTAR detection of prompt emission
  65. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  66. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  67. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  68. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  69. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  70. GRB 260310A/AT2026fgk: LBT near-infrared observations
  71. NOEMA Detection of GRB 260310A / AT 2026fgk
  72. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  73. GRB 260318A: SVOM/GRM observation
  74. The EP-WXT trigger 01709258989 is likely a flaring star
  75. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  76. GRB 260318A: GECAM-B observation
  77. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  78. Fermi GRB 260318A: Global MASTER-Net observations report
  79. GRB 260318A: Fermi GBM Final Real-time Localization
  80. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  81. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  82. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  83. GRB 260310A / AT 2026fgk: radio detection with the VLA
  84. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  85. GRB 260310A / AT2026fgk: LCO optical observations
  86. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  87. GRB 260317A: Fermi GBM Final Localization
  88. GRB 260316B: GECAM-B observation
  89. GRB 260316B: SVOM/GRM observation
  90. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  91. EP260316a: COLIBRÍ faint optical counterpart candidate
  92. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  93. GRB 260316B: AstroSat CZTI detection
  94. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  95. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  96. EP260316a: Xinglong optical upper limit
  97. GRB 260316B: Fermi GBM Final Real-time Localization
  98. EP260316a: optical upper limit with Kinder observations
  99. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  100. GRB 260314A: Glowbug gamma-ray detection

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