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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. 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"

5372 results found.

  1. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  2. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  3. IPN triangulation of GRB 260428A
  4. SVOM GRB 260504B: MASTER-OAFA optical observations
  5. Fermi GRB 260504A: Global MASTER-Net observations report
  6. EP260430a: LCO optical upper limits
  7. EP260430a: Global MASTER-Net observations report
  8. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  9. Fermi trigger No 798737427: Global MASTER-Net observations report
  10. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  11. Fermi GRB 260421C: Global MASTER-Net observations report
  12. Fermi GRB 260421B: Global MASTER-Net observations report
  13. Fermi GRB 260421A: Global MASTER-Net observations report
  14. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  15. EP260417a: Global MASTER-Net observations report
  16. Fermi GRB 260417A: Global MASTER-Net observations report
  17. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  18. EP260416a: COLIBRÍ optical counterpart candidate
  19. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  20. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  21. Fermi trigger No 797912738: Global MASTER-Net observations report
  22. GRB 260410A: Glowbug gamma-ray detection of a short burst
  23. GRB 260410A: Insight-HXMT/HE detection
  24. Konus-Wind detection of GRB 260410A (short/hard)
  25. EP260321a: SVOM/VT optical observations and color changes around peak
  26. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  27. GRB 260410A: COLIBRÍ optical upper limit
  28. GRB 260410A: Fermi GBM Observation
  29. GRB 260410A: Fermi-LAT detection
  30. GRB 260410A: Fermi GBM Final Real-time Localization
  31. EP260409a: COLIBRÍ optical upper limits
  32. EP260403a: Mephisto optical upper limits
  33. EP260321a: Upper limits from VLA radio observations
  34. EP260405a: Global MASTER-Net observations report
  35. Fermi trigger No 797039833: Global MASTER-Net observations report
  36. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  37. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  38. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  39. GRB 260330B: SVOM/ECLAIRs refined analysis
  40. EP260403a: LCO optical observations of the counterpart
  41. EP260403a: LCO optical counterpart detection
  42. GRB 260330B: SVOM/VT optical candidate
  43. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  44. GRB 260403A: AstroSat CZTI detection
  45. EP260324A / AT 2026hir: COLIBRÍ optical observations
  46. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  47. EP260329b: Mondy and Assy-Turgen optical upper limits
  48. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  49. EP260321a :Xinglong optical observations
  50. EP260327a: Xinglong optical upper limit
  51. EP260329b: GOTO detection of optical counterpart
  52. GRB 260330B: SVOM/VT optical upper limits
  53. GRB 260321A: SVOM/ECLAIRs refined analysis
  54. EP260329b: J-band upper limits with WINTER
  55. EP260329a: J-band upper limit with WINTER
  56. GRB 260330A: Glowbug gamma-ray detection
  57. GRB 260310A: VLA Multi-frequency Radio Observations
  58. Fermi GBM Sub-Threshold Detection of GRB 260330B
  59. GRB 260330B: LCO optical upper limits
  60. GRB 260330B: SVOM detection of a burst
  61. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  62. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  63. EP260329a: COLIBRÍ optical upper limit
  64. EP260329a: EP-FXT follow up observation
  65. GRB 260330A: Fermi GBM Final Real-time Localization
  66. EP260329b: Global MASTER-Net observations report
  67. Fermi trigger No 796485221: Global MASTER-Net observations report
  68. GRB 260327A: Insight-HXMT/HE detection
  69. EP 260329b: COLIBRÍ optical observations
  70. EP260329a: Optical upper limit with Kinder observations
  71. EP260329b: LCO optical observations of the counterpart
  72. GRB 260326A: Insight-HXMT/HE detection
  73. EP260329b: Einstein Probe detection of an X-ray transient
  74. EP260329a: Einstein Probe detection of an X-ray transient
  75. EP-WXT trigger 01709259209: TRT optical counterpart detection
  76. GRID detection of GRB 260326A
  77. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  78. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  79. EP260327a: SVOM/VT optical upper limits
  80. EP260327a: WINTER J-band upper limit
  81. EP260327a: COLIBRÍ optical upper limits
  82. GRB 260327A: AstroSat CZTI detection of a long burst
  83. EP260327a: Gemini-North optical upper limits
  84. EP260324a: GROWTH-India Telescope optical observation
  85. EP260327a: Global MASTER-Net observations report
  86. EP260327a: Einstein Probe detection of an X-ray transient
  87. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  88. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  89. The EP-WXT trigger 01709259173 is likely a flaring star
  90. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  91. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  92. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  93. EP260321a: JinShan near-infrared observations
  94. EP260321a: Upper limits from a neutrino search with IceCube
  95. GRID detection of GRB 260320A
  96. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  97. GRB 260310A: LBT optical observations
  98. EP260321A: Mondy optical observations
  99. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  100. The EP-WXT trigger 01709259112 is likely a flaring star

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