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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"

45509 results found.

  1. EP260329a: Einstein Probe detection of an X-ray transient
  2. EP-WXT trigger 01709259209: TRT optical counterpart detection
  3. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  4. GRID detection of GRB 260326A
  5. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  6. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  7. EP260327a: SVOM/VT optical upper limits
  8. SMA Detection of GRB 260310A / AT 2026fgk
  9. GRB 260307B: ATCA Radio Upper Limits
  10. EP260327a: WINTER J-band upper limit
  11. EP260327a: COLIBRÍ optical upper limits
  12. GRB 260327A: AstroSat CZTI detection of a long burst
  13. EP260327a: Gemini-North optical upper limits
  14. EP260324a: GROWTH-India Telescope optical observation
  15. EP260327a: Global MASTER-Net observations report
  16. EP260327a: Einstein Probe detection of an X-ray transient
  17. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  18. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  19. The EP-WXT trigger 01709259173 is likely a flaring star
  20. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  21. IPN triangulation of GRB 260320A
  22. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  23. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  24. GRB 260326A: Fermi GBM Detection
  25. EP260321a: JinShan near-infrared observations
  26. GRB 260325A: Fermi GBM Final Localization
  27. GRB 260326A: Fermi GBM Final Real-time Localization
  28. EP260321a: Upper limits from a neutrino search with IceCube
  29. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  30. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  31. IPN triangulation of GRB 260316B
  32. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  33. GRID detection of GRB 260320A
  34. EP260321a: Gemini-South confirmation of a supernova (duplicate submission)
  35. EP260321a: Gemini-South confirmation of a supernova
  36. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  37. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  38. GRB 260310A: LBT optical observations
  39. EP260321A: Mondy optical observations
  40. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  41. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  42. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  43. The EP-WXT trigger 01709259112 is likely a flaring star
  44. Fermi GRB 260323A: Global MASTER-Net observations report
  45. GRB 260323A: Fermi GBM Final Real-time Localization
  46. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  47. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  48. GRB 260322A: Fermi GBM Final Localization
  49. GRB 260320A: Glowbug gamma-ray detection
  50. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  51. EP260321a: COLIBRÍ further optical observations and brightening
  52. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  53. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  54. EP260214b: ATCA 6 GHz detection
  55. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  56. GRB 260321A: EP-FXT follow-up observation
  57. The EP-WXT trigger 01709259045 is likely a flaring star
  58. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  59. EP260321a: GOTO detection of blue variable source
  60. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  61. EP260321a: further Kinder optical observations
  62. GRB 260321A: SVOM/VT optical upper limits
  63. EP260321a: Las Cumbres upper limit
  64. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  65. GRB 260320A: Insight-HXMT/HE detection
  66. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  67. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  68. EP260321a: SVOM/VT optical upper limit
  69. GRB 260310A: continued optical observation at Mondy
  70. Fermi GBM Sub-Threshold Detection of GRB 260321A
  71. GRB 260321A: SVOM detection of a burst
  72. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  73. EP260321a: Global MASTER-Net observations report
  74. EP260321a: Einstein Probe detection of an X-ray transient
  75. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  76. GRB 260318A: Glowbug gamma-ray detection
  77. GRB 260310A / AT 2026fgk: KAIT optical observations
  78. GRB 260320A: NuSTAR detection of prompt emission
  79. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  80. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  81. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  82. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  83. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  84. GRB 260310A/AT2026fgk: LBT near-infrared observations
  85. NOEMA Detection of GRB 260310A / AT 2026fgk
  86. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  87. GRB 260318A: SVOM/GRM observation
  88. The EP-WXT trigger 01709258989 is likely a flaring star
  89. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  90. GRB 260318A: GECAM-B observation
  91. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  92. Fermi GRB 260318A: Global MASTER-Net observations report
  93. GRB 260318A: Fermi GBM Final Real-time Localization
  94. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  95. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  96. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  97. GRB 260310A / AT 2026fgk: radio detection with the VLA
  98. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  99. GRB 260310A / AT2026fgk: LCO optical observations
  100. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation

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