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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"

36109 results found.

  1. GRB 260411B: COLIBRÍ optical observations
  2. GRB 260410B: Fermi GBM Observation
  3. GRB 260411B: Ondrejov D50 optical afterglow detection
  4. GRB 260411A: SVOM/GRM observation
  5. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  6. GRB 260411B: SVOM/GRM observation of a long burst
  7. GRB 260409A: Insight-HXMT/HE detection
  8. GRB 260411B: Fermi GBM Detection
  9. GRB 260411B: GOTO optical counterpart candidate
  10. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  11. GRB 260411B: Fermi GBM Final Real-time Localization
  12. GRB 260411A: Fermi GBM Final Real-time Localization
  13. GRB 260410A: COLIBRÍ optical upper limit
  14. GRB 260410A: Fermi GBM Observation
  15. GRB 260410B: SVOM/GRM detection of a short faint burst
  16. GRB 260410B: Fermi GBM Final Real-time Localization
  17. GRB 260410A: Fermi-LAT detection
  18. GRB 260410A: Fermi GBM Final Real-time Localization
  19. EP260321a: Chandra X-ray Non-detection
  20. GRB 260409A: Fermi GBM Final Real-time Localization
  21. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  22. GRB 260407A: GECAM-A detection
  23. GRB 260407A: Insight-HXMT/HE detection
  24. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  25. GRB 260404A: Fermi GBM Final Localization
  26. GRB 260407A: Glowbug gamma-ray detection
  27. GRB 260402A: SVOM/ECLAIRs refined analysis
  28. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  29. GRB 260310A / AT2026fgk: X-ray rebrightening
  30. EP260402a / GRB 260402A: Mephisto optical upper limits
  31. EP260402a/GRB 260402A: Xinglong optical upper limit
  32. GRID detection of GRB 260401A
  33. GRB 260407A: Fermi GBM Final Real-time Localization
  34. GRB 260403A: GECAM-B observation of a long burst
  35. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  36. GRB 260330B: SVOM/VT further optical observation
  37. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  38. GRB 260330B: SVOM/ECLAIRs refined analysis
  39. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  40. GRB 260330B: SVOM/VT optical candidate
  41. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  42. GRB 260403A: AstroSat CZTI detection
  43. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  44. GRB 260402B: GECAM-B observation
  45. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  46. GRB 260402C: NuSTAR detection of prompt emission
  47. GRB 260402C: AstroSat CZTI detection of a long burst
  48. GRB 260403A: Fermi GBM Final Real-time Localization
  49. GRB 260402B: Fermi GBM Final Real-time Localization
  50. GRB 260402A: WINTER J-band upper limit
  51. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  52. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  53. GRB 260401A: SVOM/GRM observation
  54. GRB 260401A: GECAM-B observation
  55. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  56. GRB 260402A: Kilonova-Catcher optical upper limit
  57. GRB 260402A: MASTER optical observations
  58. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  59. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  60. GRB 260402A: SVOM detection of a burst
  61. Fermi GRB 260401A: Global MASTER-Net observations report
  62. GRB 260401A: Fermi GBM Observation
  63. GRB 260401A: NuSTAR detection of prompt emission
  64. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  65. GRB 260401A: MAXI/GSC detection
  66. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  67. GRB 260401A: Fermi GBM Final Real-time Localization
  68. EP260329b: Mondy and Assy-Turgen optical upper limits
  69. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  70. EP260329b: GOTO detection of optical counterpart
  71. GRB 260330B: SVOM/VT optical upper limits
  72. Konus-Wind detection of GRB 260320A
  73. Konus-Wind detection of GRB 260316B (duplicate submission)
  74. Konus-Wind detection of GRB 260316B
  75. GRB 260321A: SVOM/ECLAIRs refined analysis
  76. EP260329b: J-band upper limits with WINTER
  77. EP260329a: J-band upper limit with WINTER
  78. GRB 260330A: Glowbug gamma-ray detection
  79. GRB 260310A: VLA Multi-frequency Radio Observations
  80. Fermi GBM Sub-Threshold Detection of GRB 260330B
  81. GRB 260330B: LCO optical upper limits
  82. GRB 260330B: SVOM detection of a burst
  83. GRB 260330A: Fermi GBM Final Real-time Localization
  84. GRB 260327A: Insight-HXMT/HE detection
  85. GRB 260326A: Insight-HXMT/HE detection
  86. GRID detection of GRB 260326A
  87. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  88. SMA Detection of GRB 260310A / AT 2026fgk
  89. GRB 260307B: ATCA Radio Upper Limits
  90. GRB 260327A: AstroSat CZTI detection of a long burst
  91. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  92. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  93. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  94. IPN triangulation of GRB 260320A
  95. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  96. GRB 260326A: Fermi GBM Detection
  97. GRB 260325A: Fermi GBM Final Localization
  98. GRB 260326A: Fermi GBM Final Real-time Localization
  99. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  100. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time

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