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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"

2445 results found.

  1. GRB 260330B: SVOM/ECLAIRs refined analysis
  2. EP260403a: LCO optical observations of the counterpart
  3. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  4. EP260403a: LCO optical counterpart detection
  5. EP260403a: COLIBRÍ optical counterpart candidate
  6. GRB 260330B: SVOM/VT optical candidate
  7. EP260403a: Einstein Probe detection of an X-ray transient
  8. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  9. GRB 260403A: AstroSat CZTI detection
  10. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  11. GRB 260402B: GECAM-B observation
  12. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  13. GRB 260402C: NuSTAR detection of prompt emission
  14. GRB 260402C: AstroSat CZTI detection of a long burst
  15. EP260324A / AT 2026hir: COLIBRÍ optical observations
  16. GRB 260403A: Fermi GBM Final Real-time Localization
  17. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  18. GRB 260402B: Fermi GBM Final Real-time Localization
  19. GRB 260402A: WINTER J-band upper limit
  20. GRB260402A: GROWTH-India Telescope optical upper limit
  21. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  22. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  23. GRB 260401A: SVOM/GRM observation
  24. GRB 260401A: GECAM-B observation
  25. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  26. GRB 260402A: MASTER optical observations
  27. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  28. GRB 260402A: SVOM detection of a burst
  29. Fermi GRB 260401A: Global MASTER-Net observations report
  30. GRB 260401A: Fermi GBM Observation
  31. GRB 260401A: NuSTAR detection of prompt emission
  32. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  33. GRB 260401A: MAXI/GSC detection
  34. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  35. GRB 260401A: Fermi GBM Final Real-time Localization
  36. EP260329b: Mondy and Assy-Turgen optical upper limits
  37. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  38. EP260321a :Xinglong optical observations
  39. EP260327a: Xinglong optical upper limit
  40. EP260329b: GOTO detection of optical counterpart
  41. GRB 260330B: SVOM/VT optical upper limits
  42. GRB 260321A: SVOM/ECLAIRs refined analysis
  43. EP260329b: J-band upper limits with WINTER
  44. EP260329a: J-band upper limit with WINTER
  45. GRB 260330A: Glowbug gamma-ray detection
  46. GRB 260310A: VLA Multi-frequency Radio Observations
  47. Fermi GBM Sub-Threshold Detection of GRB 260330B
  48. GRB 260330B: LCO optical upper limits
  49. GRB 260330B: SVOM detection of a burst
  50. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  51. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  52. EP260329a: COLIBRÍ optical upper limit
  53. EP260329a: EP-FXT follow up observation
  54. GRB 260330A: Fermi GBM Final Real-time Localization
  55. EP260329b: Global MASTER-Net observations report
  56. Fermi trigger No 796485221: Global MASTER-Net observations report
  57. GRB 260327A: Insight-HXMT/HE detection
  58. EP260329b: Optical follow-up with Kinder observations
  59. EP 260329b: COLIBRÍ optical observations
  60. EP260329a: Optical upper limit with Kinder observations
  61. EP260329b: LCO optical observations of the counterpart
  62. GRB 260326A: Insight-HXMT/HE detection
  63. EP260329b: Einstein Probe detection of an X-ray transient
  64. EP260329a: Einstein Probe detection of an X-ray transient
  65. EP-WXT trigger 01709259209: TRT optical counterpart detection
  66. GRID detection of GRB 260326A
  67. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  68. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  69. EP260327a: SVOM/VT optical upper limits
  70. SMA Detection of GRB 260310A / AT 2026fgk
  71. EP260327a: WINTER J-band upper limit
  72. EP260327a: COLIBRÍ optical upper limits
  73. GRB 260327A: AstroSat CZTI detection of a long burst
  74. EP260327a: Gemini-North optical upper limits
  75. EP260324a: GROWTH-India Telescope optical observation
  76. EP260327a: Global MASTER-Net observations report
  77. EP260327a: Einstein Probe detection of an X-ray transient
  78. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  79. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  80. The EP-WXT trigger 01709259173 is likely a flaring star
  81. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  82. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  83. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  84. GRB 260326A: Fermi GBM Detection
  85. EP260321a: JinShan near-infrared observations
  86. GRB 260325A: Fermi GBM Final Localization
  87. GRB 260326A: Fermi GBM Final Real-time Localization
  88. EP260321a: Upper limits from a neutrino search with IceCube
  89. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  90. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  91. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  92. GRID detection of GRB 260320A
  93. EP260321a: Gemini-South confirmation of a supernova
  94. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  95. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  96. GRB 260310A: LBT optical observations
  97. EP260321A: Mondy optical observations
  98. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  99. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  100. The EP-WXT trigger 01709259112 is likely a flaring star

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