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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"

26509 results found.

  1. EP260403a: COLIBRÍ optical counterpart candidate
  2. GRB 260330B: SVOM/VT optical candidate
  3. EP260403a: Einstein Probe detection of an X-ray transient
  4. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  5. GRB 260403A: AstroSat CZTI detection
  6. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  7. GRB 260402B: GECAM-B observation
  8. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  9. GRB 260402C: NuSTAR detection of prompt emission
  10. GRB 260402C: AstroSat CZTI detection of a long burst
  11. EP260324A / AT 2026hir: COLIBRÍ optical observations
  12. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  13. GRB 260402A: WINTER J-band upper limit
  14. GRB260402A: GROWTH-India Telescope optical upper limit
  15. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  16. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  17. GRB 260401A: SVOM/GRM observation
  18. GRB 260401A: GECAM-B observation
  19. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  20. GRB 260402A: Kilonova-Catcher optical upper limit
  21. GRB 260402A: MASTER optical observations
  22. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  23. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  24. GRB 260402A: SVOM detection of a burst
  25. GRB 260401A: Fermi GBM Observation
  26. GRB 260401A: NuSTAR detection of prompt emission
  27. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  28. GRB 260401A: MAXI/GSC detection
  29. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  30. EP260327a: Xinglong optical upper limit
  31. EP260329b: GOTO detection of optical counterpart
  32. GRB 260330B: SVOM/VT optical upper limits
  33. Konus-Wind detection of GRB 260320A
  34. Konus-Wind detection of GRB 260316B
  35. GRB 260321A: SVOM/ECLAIRs refined analysis
  36. EP260329b: J-band upper limits with WINTER
  37. EP260329a: J-band upper limit with WINTER
  38. GRB 260330A: Glowbug gamma-ray detection
  39. Fermi GBM Sub-Threshold Detection of GRB 260330B
  40. GRB 260330B: LCO optical upper limits
  41. GRB 260330B: SVOM detection of a burst
  42. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  43. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  44. EP260329a: COLIBRÍ optical upper limit
  45. EP260329a: EP-FXT follow up observation
  46. EP260329a: NOT optical counterpart candidate
  47. GRB 260327A: Insight-HXMT/HE detection
  48. EP260329b: Optical follow-up with Kinder observations
  49. EP 260329b: COLIBRÍ optical observations
  50. EP260329b: LCO optical observations of the counterpart
  51. GRB 260326A: Insight-HXMT/HE detection
  52. EP260329b: Einstein Probe detection of an X-ray transient
  53. EP260329a: Einstein Probe detection of an X-ray transient
  54. EP-WXT trigger 01709259209: TRT optical counterpart detection
  55. GRID detection of GRB 260326A
  56. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  57. EP260327a: SVOM/VT optical upper limits
  58. GRB 260307B: ATCA Radio Upper Limits
  59. EP260327a: WINTER J-band upper limit
  60. EP260327a: COLIBRÍ optical upper limits
  61. GRB 260327A: AstroSat CZTI detection of a long burst
  62. EP260324a: GROWTH-India Telescope optical observation
  63. EP260327a: Einstein Probe detection of an X-ray transient
  64. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  65. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  66. IPN triangulation of GRB 260320A
  67. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  68. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  69. GRB 260326A: Fermi GBM Detection
  70. EP260321a: Upper limits from a neutrino search with IceCube
  71. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  72. IPN triangulation of GRB 260316B
  73. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  74. GRID detection of GRB 260320A
  75. EP260321a: Gemini-South confirmation of a supernova
  76. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  77. GRB 260310A: LBT optical observations
  78. EP260321A: Mondy optical observations
  79. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  80. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  81. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  82. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  83. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  84. GRB 260320A: Glowbug gamma-ray detection
  85. EP260321a: COLIBRÍ further optical observations and brightening
  86. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  87. EP260214b: ATCA 6 GHz detection
  88. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  89. GRB 260321A: EP-FXT follow-up observation
  90. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  91. EP260321a: GOTO detection of blue variable source
  92. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  93. GRB 260321A: SVOM/VT optical upper limits
  94. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  95. GRB 260320A: Insight-HXMT/HE detection
  96. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  97. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  98. EP260321a: SVOM/VT optical upper limit
  99. GRB 260310A: continued optical observation at Mondy
  100. Fermi GBM Sub-Threshold Detection of GRB 260321A

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