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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"

28260 results found.

  1. GRB 260401A: SVOM/GRM observation
  2. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  3. GRB 260402A: Kilonova-Catcher optical upper limit
  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: NuSTAR detection of prompt emission
  11. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  12. GRB 260401A: MAXI/GSC detection
  13. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  14. GRB 260401A: Fermi GBM Final Real-time Localization
  15. EP260329b: Mondy and Assy-Turgen optical upper limits
  16. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  17. EP260321a :Xinglong optical observations
  18. EP260327a: Xinglong optical upper limit
  19. GRB 260330B: SVOM/VT optical upper limits
  20. Konus-Wind detection of GRB 260320A
  21. GRB 260321A: SVOM/ECLAIRs refined analysis
  22. EP260329b: J-band upper limits with WINTER
  23. EP260329a: J-band upper limit with WINTER
  24. GRB 260330A: Glowbug gamma-ray detection
  25. Fermi GBM Sub-Threshold Detection of GRB 260330B
  26. GRB 260330B: LCO optical upper limits
  27. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  28. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  29. EP260329a: COLIBRÍ optical upper limit
  30. EP260329a: EP-FXT follow up observation
  31. EP260329a: NOT optical counterpart candidate
  32. EP260329b: Global MASTER-Net observations report
  33. Fermi trigger No 796485221: Global MASTER-Net observations report
  34. GRB 260327A: Insight-HXMT/HE detection
  35. EP260329b: Optical follow-up with Kinder observations
  36. EP 260329b: COLIBRÍ optical observations
  37. EP260329a: Optical upper limit with Kinder observations
  38. EP260329b: LCO optical observations of the counterpart
  39. GRB 260326A: Insight-HXMT/HE detection
  40. EP260329b: Einstein Probe detection of an X-ray transient
  41. EP260329a: Einstein Probe detection of an X-ray transient
  42. EP-WXT trigger 01709259209: TRT optical counterpart detection
  43. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  44. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  45. EP260327a: SVOM/VT optical upper limits
  46. EP260327a: WINTER J-band upper limit
  47. EP260327a: COLIBRÍ optical upper limits
  48. EP260327a: Gemini-North optical upper limits
  49. EP260324a: GROWTH-India Telescope optical observation
  50. EP260327a: Global MASTER-Net observations report
  51. EP260327a: Einstein Probe detection of an X-ray transient
  52. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  53. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  54. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  55. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  56. GRB 260326A: Fermi GBM Detection
  57. EP260321a: JinShan near-infrared observations
  58. EP260321a: Upper limits from a neutrino search with IceCube
  59. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  60. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  61. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  62. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  63. Fermi GRB 260323A: Global MASTER-Net observations report
  64. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  65. GRB 260320A: Glowbug gamma-ray detection
  66. EP260321a: COLIBRÍ further optical observations and brightening
  67. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  68. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  69. GRB 260321A: EP-FXT follow-up observation
  70. EP260321a: GOTO detection of blue variable source
  71. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  72. EP260321a: further Kinder optical observations
  73. GRB 260321A: SVOM/VT optical upper limits
  74. EP260321a: Las Cumbres upper limit
  75. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  76. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  77. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  78. EP260321a: SVOM/VT optical upper limit
  79. Fermi GBM Sub-Threshold Detection of GRB 260321A
  80. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  81. EP260321a: Global MASTER-Net observations report
  82. EP260321a: Einstein Probe detection of an X-ray transient
  83. GRB 260318A: Glowbug gamma-ray detection
  84. GRB 260310A / AT 2026fgk: KAIT optical observations
  85. GRB 260320A: NuSTAR detection of prompt emission
  86. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  87. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  88. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  89. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  90. GRB 260318A: SVOM/GRM observation
  91. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  92. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  93. Fermi GRB 260318A: Global MASTER-Net observations report
  94. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  95. GRB 260310A / AT 2026fgk: radio detection with the VLA
  96. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  97. GRB 260310A / AT2026fgk: LCO optical observations
  98. GRB 260316B: SVOM/GRM observation
  99. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  100. EP260316a: COLIBRÍ faint optical counterpart candidate

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