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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"

15246 results found.

  1. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  2. Konus-Wind detection of GRB 260411B
  3. GRB 260417A: AstroSat CZTI detection
  4. IPN triangulation of GRB 260411B
  5. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  6. EP260416a: KAIT optical upper limit
  7. GRB 260414A: Insight-HXMT/HE detection
  8. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  9. EP260416a: WFST optical observations and rebrightening
  10. EP260416a: SVOM/VT optical observation
  11. GRB 260411B: Glowbug gamma-ray detection
  12. GRB 260415A: Insight-HXMT/HE detection
  13. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  14. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  15. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  16. GRB 260414A: Glowbug gamma-ray detection
  17. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  18. EP260321a: CMO SAI J,K observations
  19. GRB 260412A: Insight-HXMT/HE detection
  20. GRB 260410B: Insight-HXMT/HE detection
  21. GRB 260410A: Insight-HXMT/HE detection
  22. Konus-Wind detection of GRB 260410A (short/hard)
  23. GRB 260411B: GECAM-B observation of a long burst
  24. GRB 260412A: GECAM-B observation of a long burst
  25. GRB 260412A: Fermi GBM Observation
  26. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  27. GRB 260411B: Fermi-LAT detection
  28. GRB 260412A: SVOM detection of a long burst
  29. GRB 260411B: COLIBRÍ optical observations
  30. GRB 260410B: Fermi GBM Observation
  31. GRB 260411A: SVOM/GRM observation
  32. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  33. GRB 260411B: SVOM/GRM observation of a long burst
  34. GRB 260409A: Insight-HXMT/HE detection
  35. GRB 260411B: Fermi GBM Detection
  36. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  37. EP-WXT01709259790: Optical Upper limits with kinder observations
  38. GRB 260410A: Fermi GBM Observation
  39. GRB 260410B: SVOM/GRM detection of a short faint burst
  40. GRB 260410A: Fermi-LAT detection
  41. GRB 260407A: GECAM-A detection
  42. GRB 260407A: Insight-HXMT/HE detection
  43. GRB 260402A: SVOM/ECLAIRs refined analysis
  44. GRB 260310A / AT2026fgk: X-ray rebrightening
  45. EP260402a / GRB 260402A: Mephisto optical upper limits
  46. EP260403a: Mephisto optical upper limits
  47. GRID detection of GRB 260401A
  48. GRB 260403A: GECAM-B observation of a long burst
  49. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  50. GRB 260330B: SVOM/ECLAIRs refined analysis
  51. EP260403a: LCO optical observations of the counterpart
  52. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  53. EP260403a: LCO optical counterpart detection
  54. GRB 260403A: AstroSat CZTI detection
  55. GRB 260402B: GECAM-B observation
  56. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  57. GRB 260402C: AstroSat CZTI detection of a long burst
  58. EP260324A / AT 2026hir: COLIBRÍ optical observations
  59. GRB 260402A: WINTER J-band upper limit
  60. GRB260402A: GROWTH-India Telescope optical upper limit
  61. GRB 260401A: SVOM/GRM observation
  62. GRB 260401A: GECAM-B observation
  63. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  64. GRB 260402A: SVOM detection of a burst
  65. GRB 260401A: Fermi GBM Observation
  66. EP260329b: Mondy and Assy-Turgen optical upper limits
  67. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  68. EP260329b: GOTO detection of optical counterpart
  69. Konus-Wind detection of GRB 260320A
  70. Konus-Wind detection of GRB 260316B
  71. GRB 260321A: SVOM/ECLAIRs refined analysis
  72. GRB 260310A: VLA Multi-frequency Radio Observations
  73. GRB 260330B: SVOM detection of a burst
  74. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  75. EP260329a: COLIBRÍ optical upper limit
  76. EP260329a: EP-FXT follow up observation
  77. GRB 260327A: Insight-HXMT/HE detection
  78. EP260329b: Optical follow-up with Kinder observations
  79. EP 260329b: COLIBRÍ optical observations
  80. EP260329a: Optical upper limit with Kinder observations
  81. EP260329b: LCO optical observations of the counterpart
  82. GRB 260326A: Insight-HXMT/HE detection
  83. EP260329b: Einstein Probe detection of an X-ray transient
  84. EP-WXT trigger 01709259209: TRT optical counterpart detection
  85. GRID detection of GRB 260326A
  86. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  87. GRB 260327A: AstroSat CZTI detection of a long burst
  88. EP260324a: GROWTH-India Telescope optical observation
  89. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  90. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  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. GRB 260326A: Fermi GBM Detection
  94. EP260321a: Upper limits from a neutrino search with IceCube
  95. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  96. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  97. GRID detection of GRB 260320A
  98. GRB 260310A: LBT optical observations
  99. EP260321A: Mondy optical observations
  100. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions

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