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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"

42876 results found.

  1. GRB 260410A: Fermi-LAT detection
  2. GRB 260410A: Fermi GBM Final Real-time Localization
  3. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  4. EP260321a: Chandra X-ray Non-detection
  5. GRB 260409A: Fermi GBM Final Real-time Localization
  6. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  7. The EP-WXT trigger 01709259773 is likely a flaring star
  8. GRB 260407A: GECAM-A detection
  9. GRB 260407A: Insight-HXMT/HE detection
  10. EP260409a: SVOM/VT optical upper limits
  11. EP260409a: COLIBRÍ optical upper limits
  12. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  13. EP260409a: Global MASTER-Net observations report
  14. EP260409a: Einstein Probe detection of an X-ray transient
  15. GRB 260404A: Fermi GBM Final Localization
  16. GRB 260407A: Glowbug gamma-ray detection
  17. GRB 260402A: SVOM/ECLAIRs refined analysis
  18. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  19. GRB 260310A / AT2026fgk: X-ray rebrightening
  20. EP260402a / GRB 260402A: Mephisto optical upper limits
  21. EP260403a: Mephisto optical upper limits
  22. EP260321a: Upper limits from VLA radio observations
  23. GRID detection of GRB 260401A
  24. EP260321a: uGMRT observations
  25. GRB 260407A: Fermi GBM Final Real-time Localization
  26. EP260405a: GMOS-N optical upper limits
  27. EP260405a: SVOM/VT optical upper limits
  28. EP260405a: Global MASTER-Net observations report
  29. EP260405a: Einstein Probe detection of a fast X-ray transient
  30. The EP-WXT trigger 01709259621 is likely a flaring star
  31. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  32. The EP-WXT trigger 01709259615 is likely a flaring star
  33. Fermi trigger No 797039833: Global MASTER-Net observations report
  34. GRB 260403A: GECAM-B observation of a long burst
  35. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  36. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  37. The EP-WXT trigger 01709259586 is likely a flaring star
  38. GRB 260330B: SVOM/VT further optical observation
  39. GRB 260330B: SVOM/ECLAIRs refined analysis
  40. EP260403a: LCO optical observations of the counterpart
  41. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  42. EP260403a: LCO optical counterpart detection
  43. EP260403a: COLIBRÍ optical counterpart candidate
  44. GRB 260330B: SVOM/VT optical candidate
  45. EP260403a: Einstein Probe detection of an X-ray transient
  46. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  47. GRB 260403A: AstroSat CZTI detection
  48. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  49. GRB 260402B: GECAM-B observation
  50. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  51. GRB 260402C: NuSTAR detection of prompt emission
  52. GRB 260402C: AstroSat CZTI detection of a long burst
  53. EP260324A / AT 2026hir: COLIBRÍ optical observations
  54. GRB 260403A: Fermi GBM Final Real-time Localization
  55. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  56. GRB 260402B: Fermi GBM Final Real-time Localization
  57. GRB 260402A: WINTER J-band upper limit
  58. GRB260402A: GROWTH-India Telescope optical upper limit
  59. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  60. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  61. GRB 260401A: SVOM/GRM observation
  62. GRB 260401A: GECAM-B observation
  63. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  64. GRB 260402A: Kilonova-Catcher optical upper limit
  65. GRB 260402A: MASTER optical observations
  66. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  67. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  68. GRB 260402A: SVOM detection of a burst
  69. Fermi GRB 260401A: Global MASTER-Net observations report
  70. GRB 260401A: Fermi GBM Observation
  71. GRB 260401A: NuSTAR detection of prompt emission
  72. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  73. GRB 260401A: MAXI/GSC detection
  74. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  75. GRB 260401A: Fermi GBM Final Real-time Localization
  76. EP260329b: Mondy and Assy-Turgen optical upper limits
  77. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  78. EP260321a :Xinglong optical observations
  79. EP260329b: GOTO detection of optical counterpart
  80. GRB 260330B: SVOM/VT optical upper limits
  81. Konus-Wind detection of GRB 260320A
  82. Konus-Wind detection of GRB 260316B
  83. GRB 260321A: SVOM/ECLAIRs refined analysis
  84. EP260329b: J-band upper limits with WINTER
  85. EP260329a: J-band upper limit with WINTER
  86. GRB 260330A: Glowbug gamma-ray detection
  87. GRB 260310A: VLA Multi-frequency Radio Observations
  88. Fermi GBM Sub-Threshold Detection of GRB 260330B
  89. GRB 260330B: LCO optical upper limits
  90. GRB 260330B: SVOM detection of a burst
  91. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  92. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  93. EP260329a: COLIBRÍ optical upper limit
  94. EP260329a: EP-FXT follow up observation
  95. EP260329a: NOT optical counterpart candidate
  96. GRB 260330A: Fermi GBM Final Real-time Localization
  97. EP260329b: Global MASTER-Net observations report
  98. Fermi trigger No 796485221: Global MASTER-Net observations report
  99. GRB 260327A: Insight-HXMT/HE detection
  100. EP260329b: Optical follow-up with Kinder observations

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