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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"

40513 results found.

  1. GRB 260415B: NuSTAR detection of long prompt emission
  2. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  3. GRB 260415B: Fermi GBM Final Localization
  4. GRB 260415A: Fermi GBM Final Real-time Localization
  5. Fermi trigger No 797912738: Global MASTER-Net observations report
  6. GRB 260414A: Glowbug gamma-ray detection
  7. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  8. EP260321a: CMO SAI J,K observations
  9. GRB 260412A: Insight-HXMT/HE detection
  10. GRB 260414A: Fermi GBM Final Real-time Localization
  11. The EP-WXT trigger 01709260122 is likely a flaring star
  12. Fermi GRB 260413A: Global MASTER-Net observations report
  13. GRB 260410A: Glowbug gamma-ray detection of a short burst
  14. GRB 260413A: Fermi GBM Final Real-time Localization
  15. GRB 260410B: Insight-HXMT/HE detection
  16. GRB 260410A: Insight-HXMT/HE detection
  17. Konus-Wind detection of GRB 260410A (short/hard)
  18. GRB 260411B: GECAM-B observation of a long burst
  19. EP260321a: SVOM/VT optical observations and color changes around peak
  20. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  21. The EP-WXT trigger 01709260010 is likely a flaring star
  22. GRB 260412A: GECAM-B observation of a long burst
  23. Fermi GRB 260412A: Global MASTER-Net observations report
  24. GRB 260412A: Fermi GBM Observation
  25. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  26. GRB 260411B: Fermi-LAT detection
  27. GRB 260412A: SVOM detection of a long burst
  28. GRB 260412A: Fermi GBM Final Real-time Localization
  29. GRB 260411B: COLIBRÍ optical observations
  30. GRB 260410B: Fermi GBM Observation
  31. GRB 260411B: Ondrejov D50 optical afterglow detection
  32. GRB260411B: 3.6m DOT optical observation
  33. GRB 260411A: SVOM/GRM observation
  34. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  35. GRB 260411B: SVOM/GRM observation of a long burst
  36. GRB 260409A: Insight-HXMT/HE detection
  37. GRB 260411B: Fermi GBM Detection
  38. GRB 260411B: GOTO optical counterpart candidate
  39. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  40. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  41. GRB 260411B: Fermi GBM Final Real-time Localization
  42. GRB 260411A: Fermi GBM Final Real-time Localization
  43. GRB 260410A: COLIBRÍ optical upper limit
  44. EP-WXT01709259790: Optical Upper limits with kinder observations
  45. GRB 260410A: Fermi GBM Observation
  46. GRB 260410B: SVOM/GRM detection of a short faint burst
  47. The EP-WXT trigger 01709259790 is likely a flaring star
  48. GRB 260410B: Fermi GBM Final Real-time Localization
  49. EP-WXT01709259790: Xinglong optical upper limit
  50. GRB 260410A: Fermi-LAT detection
  51. GRB 260410A: Fermi GBM Final Real-time Localization
  52. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  53. EP260321a: Chandra X-ray Non-detection
  54. GRB 260409A: Fermi GBM Final Real-time Localization
  55. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  56. The EP-WXT trigger 01709259773 is likely a flaring star
  57. GRB 260407A: GECAM-A detection
  58. GRB 260407A: Insight-HXMT/HE detection
  59. EP260409a: SVOM/VT optical upper limits
  60. EP260409a: COLIBRÍ optical upper limits
  61. EP260409a: Global MASTER-Net observations report
  62. EP260409a: Einstein Probe detection of an X-ray transient
  63. EP260321a: VLA radio detection
  64. GRB 260404A: Fermi GBM Final Localization
  65. GRB 260407A: Glowbug gamma-ray detection
  66. GRB 260402A: SVOM/ECLAIRs refined analysis
  67. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  68. GRB 260310A / AT2026fgk: X-ray rebrightening
  69. EP260402a / GRB 260402A: Mephisto optical upper limits
  70. EP-WXT01709259586: Xinglong optical upper limit
  71. EP260403a: Mephisto optical upper limits
  72. EP260402a/GRB 260402A: Xinglong optical upper limit
  73. EP260321a: Upper limits from VLA radio observations
  74. GRID detection of GRB 260401A
  75. EP260321a: uGMRT observations
  76. GRB 260407A: Fermi GBM Final Real-time Localization
  77. EP260405a: SVOM/VT optical upper limits
  78. EP260405a: Global MASTER-Net observations report
  79. EP260405a: Einstein Probe detection of a fast X-ray transient
  80. The EP-WXT trigger 01709259621 is likely a flaring star
  81. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  82. The EP-WXT trigger 01709259615 is likely a flaring star
  83. Fermi trigger No 797039833: Global MASTER-Net observations report
  84. GRB 260403A: GECAM-B observation of a long burst
  85. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  86. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  87. The EP-WXT trigger 01709259586 is likely a flaring star
  88. GRB 260330B: SVOM/VT further optical observation
  89. GRB 260330B: SVOM/ECLAIRs refined analysis
  90. EP260403a: LCO optical observations of the counterpart
  91. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  92. EP260403a: LCO optical counterpart detection
  93. EP260403a: COLIBRÍ optical counterpart candidate
  94. GRB 260330B: SVOM/VT optical candidate
  95. EP260403a: Einstein Probe detection of an X-ray transient
  96. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  97. GRB 260403A: AstroSat CZTI detection
  98. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  99. GRB 260402B: GECAM-B observation
  100. EP260402a/GRB 260402A: Jinshan near-infrared upper limit

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