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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"

15554 results found.

  1. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  2. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  3. EP260321a: CMO SAI J,K observations
  4. EP260321a: SVOM/VT optical observations and color changes around peak
  5. GRB 260411B: Fermi-LAT detection
  6. GRB 260412A: SVOM detection of a long burst
  7. GRB 260411B: COLIBRÍ optical observations
  8. GRB 260411B: Ondrejov D50 optical afterglow detection
  9. GRB260411B: 3.6m DOT optical observation
  10. GRB 260411A: SVOM/GRM observation
  11. GRB 260411B: SVOM/GRM observation of a long burst
  12. GRB 260411B: Fermi GBM Detection
  13. GRB 260411B: GOTO optical counterpart candidate
  14. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  15. GRB 260410A: COLIBRÍ optical upper limit
  16. EP-WXT01709259790: Optical Upper limits with kinder observations
  17. EP-WXT01709259790: Xinglong optical upper limit
  18. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  19. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  20. EP260409a: SVOM/VT optical upper limits
  21. EP260409a: COLIBRÍ optical upper limits
  22. GRB 260310A / AT2026fgk: X-ray rebrightening
  23. EP260402a / GRB 260402A: Mephisto optical upper limits
  24. EP-WXT01709259586: Xinglong optical upper limit
  25. EP260403a: Mephisto optical upper limits
  26. EP260402a/GRB 260402A: Xinglong optical upper limit
  27. EP260321a: Upper limits from VLA radio observations
  28. EP260321a: uGMRT observations
  29. EP260405a: GMOS-N optical upper limits
  30. EP260405a: SVOM/VT optical upper limits
  31. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  32. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  33. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  34. GRB 260330B: SVOM/VT further optical observation
  35. EP260403a: LCO optical observations of the counterpart
  36. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  37. EP260403a: LCO optical counterpart detection
  38. EP260403a: COLIBRÍ optical counterpart candidate
  39. GRB 260330B: SVOM/VT optical candidate
  40. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  41. EP260324A / AT 2026hir: COLIBRÍ optical observations
  42. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  43. GRB 260402A: WINTER J-band upper limit
  44. GRB260402A: GROWTH-India Telescope optical upper limit
  45. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  46. GRB 260401A: SVOM/GRM observation
  47. GRB 260402A: Kilonova-Catcher optical upper limit
  48. GRB 260402A: MASTER optical observations
  49. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  50. EP260329b: Mondy and Assy-Turgen optical upper limits
  51. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  52. EP260321a :Xinglong optical observations
  53. EP260327a: Xinglong optical upper limit
  54. EP260329b: GOTO detection of optical counterpart
  55. GRB 260330B: SVOM/VT optical upper limits
  56. GRB 260321A: SVOM/ECLAIRs refined analysis
  57. EP260329b: J-band upper limits with WINTER
  58. EP260329a: J-band upper limit with WINTER
  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. EP260329a: NOT optical counterpart candidate
  66. EP260329b: Optical follow-up with Kinder observations
  67. EP 260329b: COLIBRÍ optical observations
  68. EP260329a: Optical upper limit with Kinder observations
  69. EP260329b: LCO optical observations of the counterpart
  70. EP260329b: Einstein Probe detection of an X-ray transient
  71. EP-WXT trigger 01709259209: TRT optical counterpart detection
  72. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  73. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  74. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  75. EP260327a: SVOM/VT optical upper limits
  76. EP260327a: WINTER J-band upper limit
  77. EP260327a: COLIBRÍ optical upper limits
  78. EP260327a: Gemini-North optical upper limits
  79. EP260324a: GROWTH-India Telescope optical observation
  80. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  81. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  82. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  83. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  84. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  85. EP260321a: JinShan near-infrared observations
  86. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  87. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  88. EP260321a: Gemini-South confirmation of a supernova
  89. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  90. GRB 260310A: LBT optical observations
  91. EP260321A: Mondy optical observations
  92. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  93. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  94. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  95. EP260321a: COLIBRÍ further optical observations and brightening
  96. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  97. EP260214b: ATCA 6 GHz detection
  98. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  99. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  100. EP260321a: GOTO detection of blue variable source

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