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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"

28126 results found.

  1. GOTO26djh/AT2026jpw : MASTER OT observation
  2. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  3. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  4. GRB 260415B: NuSTAR detection of long prompt emission
  5. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  6. Fermi trigger No 797912738: Global MASTER-Net observations report
  7. GRB 260414A: Glowbug gamma-ray detection
  8. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  9. EP260321a: CMO SAI J,K observations
  10. Fermi GRB 260413A: Global MASTER-Net observations report
  11. GRB 260410A: Glowbug gamma-ray detection of a short burst
  12. Fermi GRB 260412A: Global MASTER-Net observations report
  13. GRB 260412A: Fermi GBM Observation
  14. GRB 260411B: Fermi-LAT detection
  15. GRB 260411B: COLIBRÍ optical observations
  16. GRB 260410B: Fermi GBM Observation
  17. GRB260411B: 3.6m DOT optical observation
  18. GRB 260411A: SVOM/GRM observation
  19. GRB 260411B: SVOM/GRM observation of a long burst
  20. GRB 260409A: Insight-HXMT/HE detection
  21. GRB 260411B: Fermi GBM Detection
  22. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  23. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  24. GRB 260410A: COLIBRÍ optical upper limit
  25. EP-WXT01709259790: Optical Upper limits with kinder observations
  26. GRB 260410A: Fermi GBM Observation
  27. GRB 260410B: SVOM/GRM detection of a short faint burst
  28. EP-WXT01709259790: Xinglong optical upper limit
  29. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  30. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  31. EP260409a: COLIBRÍ optical upper limits
  32. EP260409a: Global MASTER-Net observations report
  33. EP260409a: Einstein Probe detection of an X-ray transient
  34. EP260321a: VLA radio detection
  35. GRB 260407A: Glowbug gamma-ray detection
  36. GRB 260402A: SVOM/ECLAIRs refined analysis
  37. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  38. EP260402a / GRB 260402A: Mephisto optical upper limits
  39. EP-WXT01709259586: Xinglong optical upper limit
  40. EP260403a: Mephisto optical upper limits
  41. EP260402a/GRB 260402A: Xinglong optical upper limit
  42. EP260405a: GMOS-N optical upper limits
  43. EP260405a: Global MASTER-Net observations report
  44. EP260405a: Einstein Probe detection of a fast X-ray transient
  45. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  46. Fermi trigger No 797039833: Global MASTER-Net observations report
  47. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  48. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  49. The EP-WXT trigger 01709259586 is likely a flaring star
  50. GRB 260330B: SVOM/VT further optical observation
  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. EP260403a: COLIBRÍ optical counterpart candidate
  55. GRB 260330B: SVOM/VT optical candidate
  56. EP260403a: Einstein Probe detection of an X-ray transient
  57. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  58. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  59. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  60. GRB 260402C: NuSTAR detection of prompt emission
  61. GRB 260402C: AstroSat CZTI detection of a long burst
  62. EP260324A / AT 2026hir: COLIBRÍ optical observations
  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. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  67. GRB 260401A: SVOM/GRM observation
  68. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  69. GRB 260402A: Kilonova-Catcher optical upper limit
  70. GRB 260402A: MASTER optical observations
  71. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  72. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  73. GRB 260402A: SVOM detection of a burst
  74. Fermi GRB 260401A: Global MASTER-Net observations report
  75. GRB 260401A: Fermi GBM Observation
  76. GRB 260401A: NuSTAR detection of prompt emission
  77. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  78. GRB 260401A: MAXI/GSC detection
  79. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  80. GRB 260401A: Fermi GBM Final Real-time Localization
  81. EP260329b: Mondy and Assy-Turgen optical upper limits
  82. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  83. EP260321a :Xinglong optical observations
  84. EP260327a: Xinglong optical upper limit
  85. GRB 260330B: SVOM/VT optical upper limits
  86. Konus-Wind detection of GRB 260320A
  87. GRB 260321A: SVOM/ECLAIRs refined analysis
  88. EP260329b: J-band upper limits with WINTER
  89. EP260329a: J-band upper limit with WINTER
  90. GRB 260330A: Glowbug gamma-ray detection
  91. Fermi GBM Sub-Threshold Detection of GRB 260330B
  92. GRB 260330B: LCO optical upper limits
  93. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  94. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  95. EP260329a: COLIBRÍ optical upper limit
  96. EP260329a: EP-FXT follow up observation
  97. EP260329a: NOT optical counterpart candidate
  98. EP260329b: Global MASTER-Net observations report
  99. Fermi trigger No 796485221: Global MASTER-Net observations report
  100. GRB 260327A: Insight-HXMT/HE detection

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