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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. GRB 251011B: Fermi GBM Observation
  2. GRB 251011B : MASTER optical observations
  3. GRB 251011C: Fermi GBM Final Real-time Localization
  4. GRB 251011B: Enhanced Swift-XRT position
  5. GRB 251010A: AstroSat CZTI detection
  6. GRB 251011A: AstroSat CZTI detection
  7. GRB 251009B: SVOM/GRM observation of short GRB
  8. GRB 251011B: Swift detection of a burst
  9. GRB 251011B: Fermi GBM Final Real-time Localization
  10. GRB 251011A: Fermi GBM Final Real-time Localization
  11. Fermi Gamma-ray Burst Monitor trigger 781824269/251010892 is not a GRB
  12. GRB 251007B: Swift/UVOT Upper Limits
  13. GRB 251010A: Fermi GBM Final Real-time Localization
  14. GRB251007A: Swift/UVOT Detection
  15. GRB 251009A: GECAM-B detection of a short burst
  16. GRB 251009A: Insight-HXMT detection of a short burst
  17. GRB 251009B (short): Glowbug gamma-ray detection
  18. GRB 251009B: Insight-HXMT detection of a short burst
  19. GRB 251007A: Swift-BAT refined analysis
  20. GRB 251009A: SVOM/GRM observation of short GRB with possible tail emission
  21. GRB 251007A: SVOM/GRM observation
  22. GRB 251007A: Insight-HXMT detection
  23. GRB 251006A: CALET Gamma-Ray Burst Monitor detection
  24. GRB 251007B - SVOM/ECLAIRs refined analysis
  25. SVOM/sb25101004: SVOM detection of a stellar flare
  26. GRB 251009A: Fermi GBM Final Localization
  27. GRB 250916A: TERI Gamma-ray detection
  28. GRB 250919A: TERI gamma-ray detection
  29. EP251006a: Global MASTER-Net observations report
  30. GRB 251006A: Fermi GBM Observation
  31. GRB 251007A: 1.5m OSN and 2.2m CAHA optical follow-up
  32. GRB 251002A - SVOM/ECLAIRs refined analysis
  33. IceCube alert 141456_888784 retraction
  34. IceCube Alert 251008A: Global MASTER-Net observations report
  35. GRB 251003A: Fermi GBM Observation
  36. GRB 251006B: Fermi GBM Observation
  37. GRB 251007B: COLIBRÍ optical upper limit
  38. GRB 251007A: AstroSat CZTI detection
  39. GRB 251006B/EP251006a: EP-FXT afterglow detection
  40. GRB 250917B: iTelescope T-26 upper limit
  41. EP250911a: Koshka Zeiss-1000 Optical Upper Limit
  42. GRB 251007B: SVOM/VT optical candidate
  43. GRB 251007A: Swift-XRT refined Analysis
  44. GRB 251007A: Enhanced Swift-XRT position
  45. GRB 251007B: Swift-XRT refined Analysis
  46. GRB 251007B: Enhanced Swift-XRT position
  47. GRB 251007A: NOT optical observations
  48. GRB 251007A: AKO Optical Upper Limit
  49. GRB 251007A: CALET Gamma-Ray Burst Monitor detection
  50. GRB 251006B: Insight-HXMT detection
  51. GRB 251007A: SVOM/C-GFT optical observations
  52. GRB 251005C: PRIME J-band upper limit
  53. Swift GRB 251007B: Global MASTER-Net observations report
  54. GRB 251007A: Glowbug gamma-ray detection
  55. GRB 251007B: SVOM/C-GFT upper limit
  56. Swift GRB 251007A: Global MASTER-Net observations report
  57. GRB 251007B: SVOM detection of a faint burst
  58. GRB 251007B: Swift detection of a burst
  59. GRB 251007A: Swift detection of a burst with an optical counterpart
  60. GRB 250702B/EP250702a: JWST/NIRCam Observations
  61. GRB 251006A: Swift/BAT-GUANO subthreshold detection of a short burst
  62. GRB 251005B: Glowbug gamma-ray detection
  63. EP251003a: LCO and VST fading optical counterpart
  64. GRB 251006B/EP251006a: SVOM/VT optical candidate
  65. GRB 251006B/EP251006a: EP-FXT follow-up observation
  66. GRB 251006B: SVOM/GRM observation
  67. GRB 251006B: COLIBRÍ optical upper limit
  68. GRB 251006B/EP251006a: EP-WXT detection
  69. GRB 251005C: SVOM/VT optical fading
  70. GRB 251005C: SVOM/GRM observation of a likely short GRB
  71. LIGO/Virgo/KAGRA S251006dd: Identification of a GW compact binary merger candidate
  72. Fermi GRB 251006B: Global MASTER-Net observations report
  73. GRB 251006B: BALROG localization (Fermi Trigger 781473909 / GRB 251006837)
  74. GRB 251006B: Fermi GBM Final Real-time Localization
  75. GRB 251006A (short): Glowbug gamma-ray detection
  76. GRB 251005C: COLIBRÍ optical observations
  77. Fermi GRB 251006A: Global MASTER-Net observations report
  78. GRB 251005C: VLT/X-shooter Imaging
  79. GRB 251003A: LAST optical observations
  80. GRB 251002A: LAST optical observations
  81. GRB 251006A: Fermi GBM Final Real-time Localization
  82. GRB 251005C: SVOM/VT optical candidate
  83. GRB 251005C: AstroSat CZTI detection
  84. GRB 251005​C: Swift/UVOT Upper Limits
  85. GRB 250902A: MSU cubesats detection
  86. GRB 251005C: Swift-XRT refined Analysis
  87. GRB 251005C: Fermi GBM Observation
  88. Swift GRB 251005A: Global MASTER-Net observations report
  89. GRB 251005C: Enhanced Swift-XRT position
  90. GRB 251005C: GOTO optical upper limits
  91. Fermi trigger No 781367244: Global MASTER-Net observations report
  92. GRB 251005C: Swift detection of a burst
  93. GRB 251005B: Fermi GBM Final Real-time Localization
  94. GRB 251005A: Fermi GBM Final Localization
  95. GRB 251002A: Mondy/AZT-33IK optical observations
  96. GRB 251002A: Insight-HXMT detection
  97. GRB 251002A: Insight-HXMT detection
  98. EP251003a: Einstein Probe detection of an X-ray transient
  99. GRB 251002A: NIR observations with WINTER
  100. GRB 251003A: Swift/UVOT Upper Limits

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