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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"

42165 results found.

  1. EP260416a: Global MASTER-Net observations report
  2. EP260416a: Einstein Probe detection of an X-ray transient
  3. GOTO26djh/AT2026jpw : MASTER OT observation
  4. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  5. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  6. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  7. GRB 260415B: NuSTAR detection of long prompt emission
  8. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  9. GRB 260415B: Fermi GBM Final Localization
  10. GRB 260415A: Fermi GBM Final Real-time Localization
  11. Fermi trigger No 797912738: Global MASTER-Net observations report
  12. GRB 260414A: Glowbug gamma-ray detection
  13. EP260321a: CMO SAI J,K observations
  14. GRB 260412A: Insight-HXMT/HE detection
  15. GRB 260414A: Fermi GBM Final Real-time Localization
  16. The EP-WXT trigger 01709260122 is likely a flaring star
  17. Fermi GRB 260413A: Global MASTER-Net observations report
  18. GRB 260410A: Glowbug gamma-ray detection of a short burst
  19. GRB 260413A: Fermi GBM Final Real-time Localization
  20. GRB 260410B: Insight-HXMT/HE detection
  21. GRB 260410A: Insight-HXMT/HE detection
  22. Konus-Wind detection of GRB 260410A (short/hard)
  23. GRB 260411B: GECAM-B observation of a long burst
  24. EP260321a: SVOM/VT optical observations and color changes around peak
  25. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  26. The EP-WXT trigger 01709260010 is likely a flaring star
  27. GRB 260412A: GECAM-B observation of a long burst
  28. Fermi GRB 260412A: Global MASTER-Net observations report
  29. GRB 260412A: Fermi GBM Observation
  30. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  31. GRB 260411B: Fermi-LAT detection
  32. GRB 260412A: SVOM detection of a long burst
  33. GRB 260412A: Fermi GBM Final Real-time Localization
  34. GRB 260411B: COLIBRÍ optical observations
  35. GRB 260410B: Fermi GBM Observation
  36. GRB 260411B: Ondrejov D50 optical afterglow detection
  37. GRB260411B: 3.6m DOT optical observation
  38. GRB 260411A: SVOM/GRM observation
  39. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  40. GRB 260411B: SVOM/GRM observation of a long burst
  41. GRB 260409A: Insight-HXMT/HE detection
  42. GRB 260411B: Fermi GBM Detection
  43. GRB 260411B: GOTO optical counterpart candidate
  44. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  45. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  46. GRB 260411B: Fermi GBM Final Real-time Localization
  47. GRB 260411A: Fermi GBM Final Real-time Localization
  48. GRB 260410A: COLIBRÍ optical upper limit
  49. EP-WXT01709259790: Optical Upper limits with kinder observations
  50. GRB 260410A: Fermi GBM Observation
  51. GRB 260410B: SVOM/GRM detection of a short faint burst
  52. The EP-WXT trigger 01709259790 is likely a flaring star
  53. GRB 260410B: Fermi GBM Final Real-time Localization
  54. EP-WXT01709259790: Xinglong optical upper limit
  55. GRB 260410A: Fermi-LAT detection
  56. GRB 260410A: Fermi GBM Final Real-time Localization
  57. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  58. EP260321a: Chandra X-ray Non-detection
  59. GRB 260409A: Fermi GBM Final Real-time Localization
  60. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  61. The EP-WXT trigger 01709259773 is likely a flaring star
  62. GRB 260407A: GECAM-A detection
  63. GRB 260407A: Insight-HXMT/HE detection
  64. EP260409a: SVOM/VT optical upper limits
  65. EP260409a: COLIBRÍ optical upper limits
  66. EP260409a: Global MASTER-Net observations report
  67. EP260409a: Einstein Probe detection of an X-ray transient
  68. EP260321a: VLA radio detection
  69. GRB 260404A: Fermi GBM Final Localization
  70. GRB 260407A: Glowbug gamma-ray detection
  71. GRB 260402A: SVOM/ECLAIRs refined analysis
  72. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  73. GRB 260310A / AT2026fgk: X-ray rebrightening
  74. EP260402a / GRB 260402A: Mephisto optical upper limits
  75. EP-WXT01709259586: Xinglong optical upper limit
  76. EP260403a: Mephisto optical upper limits
  77. EP260402a/GRB 260402A: Xinglong optical upper limit
  78. EP260321a: Upper limits from VLA radio observations
  79. GRID detection of GRB 260401A
  80. EP260321a: uGMRT observations
  81. GRB 260407A: Fermi GBM Final Real-time Localization
  82. EP260405a: GMOS-N optical upper limits
  83. EP260405a: SVOM/VT optical upper limits
  84. EP260405a: Global MASTER-Net observations report
  85. EP260405a: Einstein Probe detection of a fast X-ray transient
  86. The EP-WXT trigger 01709259621 is likely a flaring star
  87. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  88. The EP-WXT trigger 01709259615 is likely a flaring star
  89. Fermi trigger No 797039833: Global MASTER-Net observations report
  90. GRB 260403A: GECAM-B observation of a long burst
  91. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  92. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  93. The EP-WXT trigger 01709259586 is likely a flaring star
  94. GRB 260330B: SVOM/VT further optical observation
  95. GRB 260330B: SVOM/ECLAIRs refined analysis
  96. EP260403a: LCO optical observations of the counterpart
  97. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  98. EP260403a: LCO optical counterpart detection
  99. EP260403a: COLIBRÍ optical counterpart candidate
  100. GRB 260330B: SVOM/VT optical candidate

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