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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. The EP-WXT trigger 01709248051 is likely a flaring star
  2. SVOM GRB251106.83: Global MASTER-Net observations report
  3. LIGO/Virgo/KAGRA S251105aj: Updated Sky localization
  4. LIGO/Virgo/KAGRA S251103f: Updated Sky localization
  5. IPN triangulation of GRB 251105B (possible sGRB with EE)
  6. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  7. GRB 251106B: SVOM/GRM observation of a short burst
  8. GRB 251106A: Swift-XRT afterglow detection
  9. GRB 251106A: Kilonova-Catcher optical upper limit
  10. Fermi GBM Sub-Threshold Detection of GRB 251106A
  11. GRB 251106A: Swift/BAT arcminute localization of a burst
  12. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  13. GRB 251106A: MASTER optical observations
  14. GRB 251106A: SVOM detection of a burst
  15. GRB 251103B: AstroSat CZTI detection
  16. GRB 251025C: TERI Gamma-ray detection
  17. GRB 251016B: TERI Gamma-ray detection
  18. GRB 251016A: TERI Gamma-ray detection of a short burst
  19. GRB 250920C: TERI Gamma-ray detection
  20. Fermi trigger No 784034269: Global MASTER-Net observations report
  21. Fermi Gamma-ray Burst Monitor trigger 784109140/251106337 is not a GRB
  22. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  23. GRB 251105A: Fermi GBM Observation
  24. GRB 251105C: Fermi GBM Final Localization Correction
  25. LIGO/Virgo/KAGRA S251031dw: Candidates from the Zwicky Transient Facility
  26. GRB 251105A: Swift/BAT-GUANO localization skymap of a burst
  27. GRB 251104A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  28. GRB 251105B: AstroSat CZTI detection of a short burst with extended emission
  29. GRB 251023A: SVOM/ECLAIRs detection of a burst through targeted search
  30. Fermi GBM Sub-Threshold Detection of GRB 251105B
  31. GRB 251103B: Swift/UVOT Upper Limits
  32. LIGO/Virgo/KAGRA S251105aj: Identification of a GW compact binary merger candidate
  33. GRB 251105B: SVOM/GRM observation of a possible short burst with extended emission
  34. Fermi GRB 251105A: Global MASTER-Net observations report
  35. GRB 251105A: Fermi GBM Final Real-time Localization
  36. Fermi Gamma-ray Burst Monitor trigger 783986701/251104920 is not a GRB
  37. GRB 251103B: Fermi GBM observation
  38. GRB 251104A: SVOM detection of a burst
  39. GRB 251028A: Insight-HXMT/HE detection
  40. GRB 251103A: Optical afterglow detection by ZTF’s public survey
  41. EP251102a: FTW optical and NIR observations
  42. GRB 251103A: WFST optical observations
  43. EP251102a: update of EP-FXT follow-up observation
  44. EP251102a: OHP/T193 optical observations
  45. GRB 251103A: OHP/T193 optical observations
  46. GRB 251103A: Xinglong 2.16m optical detection
  47. GRB 251103A: Insight-HXMT detection
  48. GRB 251103A: KAIT optical observations
  49. GRB 251103B: Nanshan/HMT optical upper limit
  50. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  51. GRB 251103A: Swift/BAT-GUANO arcminute localization of a burst
  52. GRB 251103B: MITSuME Akeno optical upper limits
  53. GRB 251103B: Swift-XRT refined Analysis
  54. Fermi GRB 251103A: Global MASTER-Net observations report
  55. LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate
  56. EP251102a: NIR observations with WINTER
  57. GRB 251103A: J-band detection with WINTER
  58. Swift GRB 251103B: Global MASTER-Net observations report
  59. GRB 251103B: GROWTH-India Telescope optical upper limits
  60. GRB 251103A: Kilonova-Catcher optical afterglow detection
  61. GRB 251103B: Enhanced Swift-XRT position
  62. GRB 251103B: Prompt enhanced Swift-XRT position
  63. GRB 251103B: Swift detection of a burst
  64. GRB 251103B: Fermi GBM Final Real-time Localization
  65. GRB 251103A: Swift/UVOT Detection
  66. GRB 251103A: Fermi GBM Observation
  67. GRB 251103A: SVOM/GRM observation
  68. GRB 251103A: Swift-XRT afterglow detection
  69. LIGO/Virgo/KAGRA S251031cq: Updated Sky localization
  70. GRB 251103A: SVOM/COLIBRÍ (FM-GFT) optical observations
  71. EP251102a: Einstein Probe detection of a fast X-ray transient
  72. GRB 251025B: OHP/T193 optical upper limit
  73. EP251102a (WXT 11900459650): LCO observations confirm COLIBRÍ candidate
  74. GRB 251103A: LCO optical observation
  75. EP251102.890: COLIBRÍ optical counterpart candidate
  76. GRB 251103A: GOTO optical afterglow detection
  77. GRB 251102A: AstroSat CZTI detection
  78. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical counterpart
  79. GRB 251103A: NOT spectroscopic redshift z = 0.76
  80. GRB 251103A: BOOTES-2/TELMA optical afterglow
  81. GRB 251103A: LCO optical afterglow detection
  82. GRB 251103A: NOT optical afterglow candidate (duplicate submission)
  83. GRB 251103A: Fermi GBM Final Localization
  84. GRB 251103A: NOT optical afterglow candidate
  85. GRB 251103A: SVOM detection of a bright burst
  86. GRB 251102B: Fermi GBM Final Real-time Localization
  87. Fermi GRB 251102A: Global MASTER-Net observations report
  88. GRB 251102A: Fermi GBM Final Real-time Localization
  89. GRB 251031A: Fermi GBM Observation
  90. LIGO/Virgo/KAGRA S251031cq: Identification of a GW compact binary merger candidate
  91. GRB 251031A: Swift/BAT-GUANO localization skymap of a burst
  92. Konus-Wind detection of GRB 251028A
  93. GRB 251031A: BALROG localization (Fermi Trigger 783588065 / GRB 251031306)
  94. GRB 251031A: Fermi GBM Final Real-time Localization
  95. GRB 251025C: SVOM/GRM observation
  96. GRB 251028A: GECAM-B detection
  97. GRB 251028A: SVOM/GRM observation
  98. IceCube-251025A: Two Transient Candidates from the Zwicky Transient Facility
  99. GRB 251028A: Fermi GBM Observation
  100. GRB 251026B: SOAR Classification of GOTO25jgl/SN2025absf as a Type Ia supernova

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