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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"

16159 results found.

  1. EP260417b: GROWTH-India Telescope optical upper limit
  2. EP260416a: Ondrejov D50 optical detection
  3. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  4. EP260416a: NOT tentative spectroscopic redshift of z =1.909
  5. EP260416a: GMG Optical Observation
  6. EP260416a: LCO observations confirm end of flaring phase
  7. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  8. EP260417a: TRT optical counterpart detection
  9. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  10. EP-WXT trigger 01709259586: KAIT optical observations
  11. EP260416a: KAIT optical upper limit
  12. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  13. EP260416a: WFST optical observations and rebrightening
  14. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  15. EP260416a: SVOM/VT optical observation
  16. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  17. EP260416a: COLIBRÍ optical counterpart candidate
  18. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  19. GOTO26djh/AT2026jpw : MASTER OT observation
  20. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  21. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  22. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  23. EP260321a: SVOM/VT optical observations and color changes around peak
  24. GRB 260411B: Fermi-LAT detection
  25. GRB 260412A: SVOM detection of a long burst
  26. GRB 260411B: COLIBRÍ optical observations
  27. GRB 260411B: Ondrejov D50 optical afterglow detection
  28. GRB260411B: 3.6m DOT optical observation
  29. GRB 260411A: SVOM/GRM observation
  30. GRB 260411B: SVOM/GRM observation of a long burst
  31. GRB 260411B: Fermi GBM Detection
  32. GRB 260411B: GOTO optical counterpart candidate
  33. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  34. GRB 260410A: COLIBRÍ optical upper limit
  35. EP-WXT01709259790: Optical Upper limits with kinder observations
  36. EP-WXT01709259790: Xinglong optical upper limit
  37. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  38. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  39. EP260409a: SVOM/VT optical upper limits
  40. EP260409a: COLIBRÍ optical upper limits
  41. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  42. GRB 260310A / AT2026fgk: X-ray rebrightening
  43. EP260402a / GRB 260402A: Mephisto optical upper limits
  44. EP-WXT01709259586: Xinglong optical upper limit
  45. EP260403a: Mephisto optical upper limits
  46. EP260402a/GRB 260402A: Xinglong optical upper limit
  47. EP260321a: Upper limits from VLA radio observations
  48. EP260321a: uGMRT observations
  49. EP260405a: GMOS-N optical upper limits
  50. EP260405a: SVOM/VT optical upper limits
  51. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  52. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  53. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  54. GRB 260330B: SVOM/VT further optical observation
  55. EP260403a: LCO optical observations of the counterpart
  56. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  57. EP260403a: LCO optical counterpart detection
  58. EP260403a: COLIBRÍ optical counterpart candidate
  59. GRB 260330B: SVOM/VT optical candidate
  60. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  61. EP260324A / AT 2026hir: COLIBRÍ optical observations
  62. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  63. GRB 260402A: WINTER J-band upper limit
  64. GRB260402A: GROWTH-India Telescope optical upper limit
  65. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  66. GRB 260401A: SVOM/GRM observation
  67. GRB 260402A: Kilonova-Catcher optical upper limit
  68. GRB 260402A: MASTER optical observations
  69. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  70. EP260329b: Mondy and Assy-Turgen optical upper limits
  71. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  72. EP260321a :Xinglong optical observations
  73. EP260327a: Xinglong optical upper limit
  74. EP260329b: GOTO detection of optical counterpart
  75. GRB 260330B: SVOM/VT optical upper limits
  76. GRB 260321A: SVOM/ECLAIRs refined analysis
  77. EP260329b: J-band upper limits with WINTER
  78. EP260329a: J-band upper limit with WINTER
  79. GRB 260330B: LCO optical upper limits
  80. GRB 260330B: SVOM detection of a burst
  81. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  82. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  83. EP260329a: COLIBRÍ optical upper limit
  84. EP260329a: EP-FXT follow up observation
  85. EP260329a: NOT optical counterpart candidate
  86. EP260329b: Optical follow-up with Kinder observations
  87. EP 260329b: COLIBRÍ optical observations
  88. EP260329a: Optical upper limit with Kinder observations
  89. EP260329b: LCO optical observations of the counterpart
  90. EP260329b: Einstein Probe detection of an X-ray transient
  91. EP-WXT trigger 01709259209: TRT optical counterpart detection
  92. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  93. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  94. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  95. EP260327a: SVOM/VT optical upper limits
  96. EP260327a: WINTER J-band upper limit
  97. EP260327a: COLIBRÍ optical upper limits
  98. EP260327a: Gemini-North optical upper limits
  99. EP260324a: GROWTH-India Telescope optical observation
  100. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova

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