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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"

42902 results found.

  1. GRB 260401A: Fermi GBM Final Real-time Localization
  2. EP260329b: Mondy and Assy-Turgen optical upper limits
  3. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  4. EP260321a :Xinglong optical observations
  5. EP260329b: GOTO detection of optical counterpart
  6. GRB 260330B: SVOM/VT optical upper limits
  7. Konus-Wind detection of GRB 260320A
  8. Konus-Wind detection of GRB 260316B
  9. GRB 260321A: SVOM/ECLAIRs refined analysis
  10. EP260329b: J-band upper limits with WINTER
  11. EP260329a: J-band upper limit with WINTER
  12. GRB 260330A: Glowbug gamma-ray detection
  13. GRB 260310A: VLA Multi-frequency Radio Observations
  14. Fermi GBM Sub-Threshold Detection of GRB 260330B
  15. GRB 260330B: LCO optical upper limits
  16. GRB 260330B: SVOM detection of a burst
  17. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  18. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  19. EP260329a: COLIBRÍ optical upper limit
  20. EP260329a: EP-FXT follow up observation
  21. EP260329a: NOT optical counterpart candidate
  22. GRB 260330A: Fermi GBM Final Real-time Localization
  23. EP260329b: Global MASTER-Net observations report
  24. Fermi trigger No 796485221: Global MASTER-Net observations report
  25. GRB 260327A: Insight-HXMT/HE detection
  26. EP260329b: Optical follow-up with Kinder observations
  27. EP 260329b: COLIBRÍ optical observations
  28. EP260329a: Optical upper limit with Kinder observations
  29. EP260329b: LCO optical observations of the counterpart
  30. GRB 260326A: Insight-HXMT/HE detection
  31. EP260329b: Einstein Probe detection of an X-ray transient
  32. EP260329a: Einstein Probe detection of an X-ray transient
  33. EP-WXT trigger 01709259209: TRT optical counterpart detection
  34. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  35. GRID detection of GRB 260326A
  36. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  37. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  38. EP260327a: SVOM/VT optical upper limits
  39. SMA Detection of GRB 260310A / AT 2026fgk
  40. GRB 260307B: ATCA Radio Upper Limits
  41. EP260327a: WINTER J-band upper limit
  42. EP260327a: COLIBRÍ optical upper limits
  43. GRB 260327A: AstroSat CZTI detection of a long burst
  44. EP260327a: Gemini-North optical upper limits
  45. EP260324a: GROWTH-India Telescope optical observation
  46. EP260327a: Global MASTER-Net observations report
  47. EP260327a: Einstein Probe detection of an X-ray transient
  48. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  49. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  50. The EP-WXT trigger 01709259173 is likely a flaring star
  51. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  52. IPN triangulation of GRB 260320A
  53. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  54. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  55. GRB 260326A: Fermi GBM Detection
  56. EP260321a: JinShan near-infrared observations
  57. GRB 260325A: Fermi GBM Final Localization
  58. GRB 260326A: Fermi GBM Final Real-time Localization
  59. EP260321a: Upper limits from a neutrino search with IceCube
  60. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  61. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  62. IPN triangulation of GRB 260316B
  63. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  64. GRID detection of GRB 260320A
  65. EP260321a: Gemini-South confirmation of a supernova
  66. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  67. GRB 260310A: LBT optical observations
  68. EP260321A: Mondy optical observations
  69. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  70. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  71. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  72. The EP-WXT trigger 01709259112 is likely a flaring star
  73. Fermi GRB 260323A: Global MASTER-Net observations report
  74. GRB 260323A: Fermi GBM Final Real-time Localization
  75. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  76. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  77. GRB 260322A: Fermi GBM Final Localization
  78. GRB 260320A: Glowbug gamma-ray detection
  79. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  80. EP260321a: COLIBRÍ further optical observations and brightening
  81. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  82. EP260214b: ATCA 6 GHz detection
  83. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  84. GRB 260321A: EP-FXT follow-up observation
  85. The EP-WXT trigger 01709259045 is likely a flaring star
  86. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  87. EP260321a: GOTO detection of blue variable source
  88. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  89. EP260321a: further Kinder optical observations
  90. GRB 260321A: SVOM/VT optical upper limits
  91. EP260321a: Las Cumbres upper limit
  92. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  93. GRB 260320A: Insight-HXMT/HE detection
  94. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  95. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  96. EP260321a: SVOM/VT optical upper limit
  97. GRB 260310A: continued optical observation at Mondy
  98. Fermi GBM Sub-Threshold Detection of GRB 260321A
  99. GRB 260321A: SVOM detection of a burst
  100. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle

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