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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"

27604 results found.

  1. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  2. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  3. GRB 260401A: SVOM/GRM observation
  4. GRB 260402A: MASTER optical observations
  5. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  6. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  7. GRB 260402A: SVOM detection of a burst
  8. Fermi GRB 260401A: Global MASTER-Net observations report
  9. GRB 260401A: Fermi GBM Observation
  10. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  11. GRB 260401A: Fermi GBM Final Real-time Localization
  12. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  13. EP260321a :Xinglong optical observations
  14. EP260327a: Xinglong optical upper limit
  15. EP260329b: GOTO detection of optical counterpart
  16. GRB 260330B: SVOM/VT optical upper limits
  17. GRB 260321A: SVOM/ECLAIRs refined analysis
  18. EP260329b: J-band upper limits with WINTER
  19. EP260329a: J-band upper limit with WINTER
  20. Fermi GBM Sub-Threshold Detection of GRB 260330B
  21. GRB 260330B: LCO optical upper limits
  22. GRB 260330B: SVOM detection of a burst
  23. EP260329a: COLIBRÍ optical upper limit
  24. EP260329a: EP-FXT follow up observation
  25. EP260329a: NOT optical counterpart candidate
  26. GRB 260330A: Fermi GBM Final Real-time Localization
  27. EP260329b: Global MASTER-Net observations report
  28. Fermi trigger No 796485221: Global MASTER-Net observations report
  29. EP 260329b: COLIBRÍ optical observations
  30. EP260329b: LCO optical observations of the counterpart
  31. EP-WXT trigger 01709259209: TRT optical counterpart detection
  32. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  33. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  34. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  35. EP260327a: SVOM/VT optical upper limits
  36. EP260327a: WINTER J-band upper limit
  37. EP260327a: COLIBRÍ optical upper limits
  38. EP260327a: Gemini-North optical upper limits
  39. EP260324a: GROWTH-India Telescope optical observation
  40. EP260327a: Global MASTER-Net observations report
  41. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  42. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  43. The EP-WXT trigger 01709259173 is likely a flaring star
  44. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  45. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  46. GRB 260326A: Fermi GBM Detection
  47. GRB 260325A: Fermi GBM Final Localization
  48. GRB 260326A: Fermi GBM Final Real-time Localization
  49. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  50. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  51. IPN triangulation of GRB 260316B
  52. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  53. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  54. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  55. GRB 260310A: LBT optical observations
  56. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  57. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  58. The EP-WXT trigger 01709259112 is likely a flaring star
  59. Fermi GRB 260323A: Global MASTER-Net observations report
  60. GRB 260323A: Fermi GBM Final Real-time Localization
  61. GRB 260322A: Fermi GBM Final Localization
  62. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  63. EP260321a: COLIBRÍ further optical observations and brightening
  64. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  65. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  66. EP260214b: ATCA 6 GHz detection
  67. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  68. GRB 260321A: EP-FXT follow-up observation
  69. The EP-WXT trigger 01709259045 is likely a flaring star
  70. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  71. EP260321a: GOTO detection of blue variable source
  72. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  73. EP260321a: further Kinder optical observations
  74. GRB 260321A: SVOM/VT optical upper limits
  75. EP260321a: Las Cumbres upper limit
  76. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  77. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  78. EP260321a: SVOM/VT optical upper limit
  79. Fermi GBM Sub-Threshold Detection of GRB 260321A
  80. GRB 260321A: SVOM detection of a burst
  81. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  82. EP260321a: Global MASTER-Net observations report
  83. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  84. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  85. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  86. GRB 260310A/AT2026fgk: LBT near-infrared observations
  87. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  88. GRB 260318A: SVOM/GRM observation
  89. The EP-WXT trigger 01709258989 is likely a flaring star
  90. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  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. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  95. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  96. GRB 260310A / AT2026fgk: LCO optical observations
  97. GRB 260317A: Fermi GBM Final Localization
  98. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  99. EP260316a: COLIBRÍ faint optical counterpart candidate
  100. GRB 260316B: AstroSat CZTI detection

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