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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"

27602 results found.

  1. GRB 260401A: SVOM/GRM observation
  2. GRB 260402A: MASTER optical observations
  3. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  4. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  5. GRB 260402A: SVOM detection of a burst
  6. Fermi GRB 260401A: Global MASTER-Net observations report
  7. GRB 260401A: Fermi GBM Observation
  8. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  9. GRB 260401A: Fermi GBM Final Real-time Localization
  10. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  11. EP260321a :Xinglong optical observations
  12. EP260327a: Xinglong optical upper limit
  13. EP260329b: GOTO detection of optical counterpart
  14. GRB 260330B: SVOM/VT optical upper limits
  15. GRB 260321A: SVOM/ECLAIRs refined analysis
  16. EP260329b: J-band upper limits with WINTER
  17. EP260329a: J-band upper limit with WINTER
  18. Fermi GBM Sub-Threshold Detection of GRB 260330B
  19. GRB 260330B: LCO optical upper limits
  20. GRB 260330B: SVOM detection of a burst
  21. EP260329a: COLIBRÍ optical upper limit
  22. EP260329a: EP-FXT follow up observation
  23. EP260329a: NOT optical counterpart candidate
  24. GRB 260330A: Fermi GBM Final Real-time Localization
  25. EP260329b: Global MASTER-Net observations report
  26. Fermi trigger No 796485221: Global MASTER-Net observations report
  27. EP 260329b: COLIBRÍ optical observations
  28. EP260329b: LCO optical observations of the counterpart
  29. EP-WXT trigger 01709259209: TRT optical counterpart detection
  30. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  31. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  32. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  33. EP260327a: SVOM/VT optical upper limits
  34. EP260327a: WINTER J-band upper limit
  35. EP260327a: COLIBRÍ optical upper limits
  36. EP260327a: Gemini-North optical upper limits
  37. EP260324a: GROWTH-India Telescope optical observation
  38. EP260327a: Global MASTER-Net observations report
  39. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  40. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  41. The EP-WXT trigger 01709259173 is likely a flaring star
  42. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  43. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  44. GRB 260326A: Fermi GBM Detection
  45. GRB 260325A: Fermi GBM Final Localization
  46. GRB 260326A: Fermi GBM Final Real-time Localization
  47. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  48. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  49. IPN triangulation of GRB 260316B
  50. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  51. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  52. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  53. GRB 260310A: LBT optical observations
  54. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  55. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  56. The EP-WXT trigger 01709259112 is likely a flaring star
  57. Fermi GRB 260323A: Global MASTER-Net observations report
  58. GRB 260323A: Fermi GBM Final Real-time Localization
  59. GRB 260322A: Fermi GBM Final Localization
  60. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  61. EP260321a: COLIBRÍ further optical observations and brightening
  62. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  63. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  64. EP260214b: ATCA 6 GHz detection
  65. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  66. GRB 260321A: EP-FXT follow-up observation
  67. The EP-WXT trigger 01709259045 is likely a flaring star
  68. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  69. EP260321a: GOTO detection of blue variable source
  70. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  71. EP260321a: further Kinder optical observations
  72. GRB 260321A: SVOM/VT optical upper limits
  73. EP260321a: Las Cumbres upper limit
  74. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  75. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  76. EP260321a: SVOM/VT optical upper limit
  77. Fermi GBM Sub-Threshold Detection of GRB 260321A
  78. GRB 260321A: SVOM detection of a burst
  79. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  80. EP260321a: Global MASTER-Net observations report
  81. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  82. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  83. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  84. GRB 260310A/AT2026fgk: LBT near-infrared observations
  85. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  86. GRB 260318A: SVOM/GRM observation
  87. The EP-WXT trigger 01709258989 is likely a flaring star
  88. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  89. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  90. Fermi GRB 260318A: Global MASTER-Net observations report
  91. GRB 260318A: Fermi GBM Final Real-time Localization
  92. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  93. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  94. GRB 260310A / AT2026fgk: LCO optical observations
  95. GRB 260317A: Fermi GBM Final Localization
  96. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  97. EP260316a: COLIBRÍ faint optical counterpart candidate
  98. GRB 260316B: AstroSat CZTI detection
  99. EP260316a: Xinglong optical upper limit
  100. GRB 260316B: Fermi GBM Final Real-time Localization

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