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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"
  1. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  2. EP260416a: SVOM/VT optical observation
  3. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  4. GRB 260415B: Glowbug gamma-ray detection
  5. GRB 260411B: Glowbug gamma-ray detection
  6. GRB 260415A: Insight-HXMT/HE detection
  7. EP260416a: COLIBRÍ optical counterpart candidate
  8. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  9. EP260416a: Global MASTER-Net observations report
  10. EP260416a: Einstein Probe detection of an X-ray transient
  11. GOTO26djh/AT2026jpw : MASTER OT observation
  12. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  13. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  14. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  15. GRB 260415B: NuSTAR detection of long prompt emission
  16. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  17. GRB 260415B: Fermi GBM Final Localization
  18. GRB 260415A: Fermi GBM Final Real-time Localization
  19. Fermi trigger No 797912738: Global MASTER-Net observations report
  20. GRB 260414A: Glowbug gamma-ray detection
  21. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  22. EP260321a: CMO SAI J,K observations
  23. GRB 260412A: Insight-HXMT/HE detection
  24. GRB 260414A: Fermi GBM Final Real-time Localization
  25. The EP-WXT trigger 01709260122 is likely a flaring star
  26. Fermi GRB 260413A: Global MASTER-Net observations report
  27. GRB 260410A: Glowbug gamma-ray detection of a short burst
  28. GRB 260413A: Fermi GBM Final Real-time Localization
  29. GRB 260410B: Insight-HXMT/HE detection
  30. GRB 260410A: Insight-HXMT/HE detection
  31. Konus-Wind detection of GRB 260410A (short/hard)
  32. GRB 260411B: GECAM-B observation of a long burst
  33. EP260321a: SVOM/VT optical observations and color changes around peak
  34. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  35. The EP-WXT trigger 01709260010 is likely a flaring star
  36. GRB 260412A: GECAM-B observation of a long burst
  37. Fermi GRB 260412A: Global MASTER-Net observations report
  38. GRB 260412A: Fermi GBM Observation
  39. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  40. GRB 260411B: Fermi-LAT detection
  41. GRB 260412A: SVOM detection of a long burst
  42. GRB 260412A: Fermi GBM Final Real-time Localization
  43. GRB 260411B: COLIBRÍ optical observations
  44. GRB 260410B: Fermi GBM Observation
  45. GRB 260411B: Ondrejov D50 optical afterglow detection
  46. GRB260411B: 3.6m DOT optical observation
  47. GRB 260411A: SVOM/GRM observation
  48. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  49. GRB 260411B: SVOM/GRM observation of a long burst
  50. GRB 260409A: Insight-HXMT/HE detection
  51. GRB 260411B: Fermi GBM Detection
  52. GRB 260411B: GOTO optical counterpart candidate
  53. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  54. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  55. GRB 260411B: Fermi GBM Final Real-time Localization
  56. GRB 260411A: Fermi GBM Final Real-time Localization
  57. GRB 260410A: COLIBRÍ optical upper limit
  58. EP-WXT01709259790: Optical Upper limits with kinder observations
  59. GRB 260410A: Fermi GBM Observation
  60. GRB 260410B: SVOM/GRM detection of a short faint burst
  61. The EP-WXT trigger 01709259790 is likely a flaring star
  62. GRB 260410B: Fermi GBM Final Real-time Localization
  63. EP-WXT01709259790: Xinglong optical upper limit
  64. GRB 260410A: Fermi-LAT detection
  65. GRB 260410A: Fermi GBM Final Real-time Localization
  66. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  67. EP260321a: Chandra X-ray Non-detection
  68. GRB 260409A: Fermi GBM Final Real-time Localization
  69. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  70. The EP-WXT trigger 01709259773 is likely a flaring star
  71. GRB 260407A: GECAM-A detection
  72. GRB 260407A: Insight-HXMT/HE detection
  73. EP260409a: SVOM/VT optical upper limits
  74. EP260409a: COLIBRÍ optical upper limits
  75. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  76. EP260409a: Global MASTER-Net observations report
  77. EP260409a: Einstein Probe detection of an X-ray transient
  78. EP260321a: VLA radio detection
  79. GRB 260404A: Fermi GBM Final Localization
  80. GRB 260407A: Glowbug gamma-ray detection
  81. GRB 260402A: SVOM/ECLAIRs refined analysis
  82. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  83. GRB 260310A / AT2026fgk: X-ray rebrightening
  84. EP260402a / GRB 260402A: Mephisto optical upper limits
  85. EP-WXT01709259586: Xinglong optical upper limit
  86. EP260403a: Mephisto optical upper limits
  87. EP260402a/GRB 260402A: Xinglong optical upper limit
  88. EP260321a: Upper limits from VLA radio observations
  89. GRID detection of GRB 260401A
  90. EP260321a: uGMRT observations
  91. GRB 260407A: Fermi GBM Final Real-time Localization
  92. EP260405a: GMOS-N optical upper limits
  93. EP260405a: SVOM/VT optical upper limits
  94. EP260405a: Global MASTER-Net observations report
  95. EP260405a: Einstein Probe detection of a fast X-ray transient
  96. The EP-WXT trigger 01709259621 is likely a flaring star
  97. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  98. The EP-WXT trigger 01709259615 is likely a flaring star
  99. Fermi trigger No 797039833: Global MASTER-Net observations report
  100. GRB 260403A: GECAM-B observation of a long burst

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