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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"

19290 results found.

  1. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  2. EP260416a: Global MASTER-Net observations report
  3. EP260416a: Einstein Probe detection of an X-ray transient
  4. GOTO26djh/AT2026jpw : MASTER OT observation
  5. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  6. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  7. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  8. GRB 260415B: NuSTAR detection of long prompt emission
  9. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  10. GRB 260415B: Fermi GBM Final Localization
  11. GRB 260415A: Fermi GBM Final Real-time Localization
  12. Fermi trigger No 797912738: Global MASTER-Net observations report
  13. GRB 260414A: Glowbug gamma-ray detection
  14. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  15. EP260321a: CMO SAI J,K observations
  16. GRB 260412A: Insight-HXMT/HE detection
  17. GRB 260414A: Fermi GBM Final Real-time Localization
  18. The EP-WXT trigger 01709260122 is likely a flaring star
  19. Fermi GRB 260413A: Global MASTER-Net observations report
  20. GRB 260410A: Glowbug gamma-ray detection of a short burst
  21. GRB 260413A: Fermi GBM Final Real-time Localization
  22. GRB 260410B: Insight-HXMT/HE detection
  23. GRB 260410A: Insight-HXMT/HE detection
  24. GRB 260411B: GECAM-B observation of a long burst
  25. EP260321a: SVOM/VT optical observations and color changes around peak
  26. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  27. The EP-WXT trigger 01709260010 is likely a flaring star
  28. GRB 260412A: GECAM-B observation of a long burst
  29. Fermi GRB 260412A: Global MASTER-Net observations report
  30. GRB 260412A: Fermi GBM Observation
  31. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  32. GRB 260411B: Fermi-LAT detection
  33. GRB 260412A: SVOM detection of a long burst
  34. GRB 260412A: Fermi GBM Final Real-time Localization
  35. GRB 260411B: COLIBRÍ optical observations
  36. GRB 260410B: Fermi GBM Observation
  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. The EP-WXT trigger 01709259773 is likely a flaring star
  61. GRB 260407A: GECAM-A detection
  62. GRB 260407A: Insight-HXMT/HE detection
  63. EP260409a: SVOM/VT optical upper limits
  64. EP260409a: COLIBRÍ optical upper limits
  65. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  66. EP260409a: Global MASTER-Net observations report
  67. EP260409a: Einstein Probe detection of an X-ray transient
  68. GRB 260404A: Fermi GBM Final Localization
  69. GRB 260407A: Glowbug gamma-ray detection
  70. GRB 260402A: SVOM/ECLAIRs refined analysis
  71. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  72. GRB 260310A / AT2026fgk: X-ray rebrightening
  73. EP260402a / GRB 260402A: Mephisto optical upper limits
  74. EP-WXT01709259586: Xinglong optical upper limit
  75. EP260403a: Mephisto optical upper limits
  76. EP260402a/GRB 260402A: Xinglong optical upper limit
  77. EP260321a: Upper limits from VLA radio observations
  78. GRID detection of GRB 260401A
  79. EP260321a: uGMRT observations
  80. GRB 260407A: Fermi GBM Final Real-time Localization
  81. EP260405a: GMOS-N optical upper limits
  82. EP260405a: SVOM/VT optical upper limits
  83. EP260405a: Global MASTER-Net observations report
  84. EP260405a: Einstein Probe detection of a fast X-ray transient
  85. The EP-WXT trigger 01709259621 is likely a flaring star
  86. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  87. The EP-WXT trigger 01709259615 is likely a flaring star
  88. Fermi trigger No 797039833: Global MASTER-Net observations report
  89. GRB 260403A: GECAM-B observation of a long burst
  90. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  91. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  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. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  96. GRB 260330B: SVOM/ECLAIRs refined analysis
  97. EP260403a: LCO optical observations of the counterpart
  98. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  99. EP260403a: LCO optical counterpart detection
  100. EP260403a: COLIBRÍ optical counterpart candidate

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