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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 251108A: Fermi GBM Final Localization Correction
  2. Fermi trigger No 784329591: Global MASTER-Net observations report
  3. LIGO/Virgo/KAGRA S251108fi: Identification of a GW compact binary merger candidate
  4. Fermi trigger No 784279167: Global MASTER-Net observations report
  5. SVOM GRB251108.54: Global MASTER-Net observations report
  6. GRB 251102B: SVOM/GRM observation
  7. Fermi Gamma-ray Burst Monitor trigger 784279167/251108305 is not a GRB
  8. LIGO/Virgo/KAGRA S251108dn: Identification of a GW compact binary merger candidate
  9. The EP-WXT trigger 01709248051 is likely a flaring star
  10. SVOM GRB251106.83: Global MASTER-Net observations report
  11. LIGO/Virgo/KAGRA S251105aj: Updated Sky localization
  12. LIGO/Virgo/KAGRA S251103f: Updated Sky localization
  13. IPN triangulation of GRB 251105B (possible sGRB with EE)
  14. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  15. GRB 251106B: SVOM/GRM observation of a short burst
  16. GRB 251106A: Swift-XRT afterglow detection
  17. GRB 251106A: Kilonova-Catcher optical upper limit
  18. Fermi GBM Sub-Threshold Detection of GRB 251106A
  19. GRB 251106A: Swift/BAT arcminute localization of a burst
  20. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  21. GRB 251106A: MASTER optical observations
  22. GRB 251106A: SVOM detection of a burst
  23. GRB 251103B: AstroSat CZTI detection
  24. GRB 251025C: TERI Gamma-ray detection
  25. GRB 251016B: TERI Gamma-ray detection
  26. GRB 251016A: TERI Gamma-ray detection of a short burst
  27. GRB 250920C: TERI Gamma-ray detection
  28. Fermi trigger No 784034269: Global MASTER-Net observations report
  29. Fermi Gamma-ray Burst Monitor trigger 784109140/251106337 is not a GRB
  30. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  31. GRB 251105A: Fermi GBM Observation
  32. GRB 251105C: Fermi GBM Final Localization Correction
  33. LIGO/Virgo/KAGRA S251031dw: Candidates from the Zwicky Transient Facility
  34. GRB 251105A: Swift/BAT-GUANO localization skymap of a burst
  35. GRB 251104A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  36. GRB 251105B: AstroSat CZTI detection of a short burst with extended emission
  37. GRB 251023A: SVOM/ECLAIRs detection of a burst through targeted search
  38. Fermi GBM Sub-Threshold Detection of GRB 251105B
  39. GRB 251103B: Swift/UVOT Upper Limits
  40. LIGO/Virgo/KAGRA S251105aj: Identification of a GW compact binary merger candidate
  41. GRB 251105B: SVOM/GRM observation of a possible short burst with extended emission
  42. Fermi GRB 251105A: Global MASTER-Net observations report
  43. GRB 251105A: Fermi GBM Final Real-time Localization
  44. Fermi Gamma-ray Burst Monitor trigger 783986701/251104920 is not a GRB
  45. GRB 251103B: Fermi GBM observation
  46. GRB 251104A: SVOM detection of a burst
  47. GRB 251028A: Insight-HXMT/HE detection
  48. GRB 251103A: Optical afterglow detection by ZTF’s public survey
  49. EP251102a: FTW optical and NIR observations
  50. GRB 251103A: WFST optical observations
  51. EP251102a: update of EP-FXT follow-up observation
  52. EP251102a: OHP/T193 optical observations
  53. GRB 251103A: OHP/T193 optical observations
  54. GRB 251103A: Xinglong 2.16m optical detection
  55. GRB 251103A: Insight-HXMT detection
  56. GRB 251103A: KAIT optical observations
  57. GRB 251103B: Nanshan/HMT optical upper limit
  58. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  59. GRB 251103A: Swift/BAT-GUANO arcminute localization of a burst
  60. GRB 251103B: MITSuME Akeno optical upper limits
  61. GRB 251103B: Swift-XRT refined Analysis
  62. Fermi GRB 251103A: Global MASTER-Net observations report
  63. LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate
  64. EP251102a: NIR observations with WINTER
  65. GRB 251103A: J-band detection with WINTER
  66. Swift GRB 251103B: Global MASTER-Net observations report
  67. GRB 251103B: GROWTH-India Telescope optical upper limits
  68. GRB 251103A: Kilonova-Catcher optical afterglow detection
  69. GRB 251103B: Enhanced Swift-XRT position
  70. GRB 251103B: Prompt enhanced Swift-XRT position
  71. GRB 251103B: Swift detection of a burst
  72. GRB 251103B: Fermi GBM Final Real-time Localization
  73. GRB 251103A: Swift/UVOT Detection
  74. GRB 251103A: Fermi GBM Observation
  75. GRB 251103A: SVOM/GRM observation
  76. GRB 251103A: Swift-XRT afterglow detection
  77. LIGO/Virgo/KAGRA S251031cq: Updated Sky localization
  78. GRB 251103A: SVOM/COLIBRÍ (FM-GFT) optical observations
  79. EP251102a: Einstein Probe detection of a fast X-ray transient
  80. GRB 251025B: OHP/T193 optical upper limit
  81. EP251102a (WXT 11900459650): LCO observations confirm COLIBRÍ candidate
  82. GRB 251103A: LCO optical observation
  83. EP251102.890: COLIBRÍ optical counterpart candidate
  84. GRB 251103A: GOTO optical afterglow detection
  85. GRB 251102A: AstroSat CZTI detection
  86. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical counterpart
  87. GRB 251103A: NOT spectroscopic redshift z = 0.76
  88. GRB 251103A: BOOTES-2/TELMA optical afterglow
  89. GRB 251103A: LCO optical afterglow detection
  90. GRB 251103A: NOT optical afterglow candidate (duplicate submission)
  91. GRB 251103A: Fermi GBM Final Localization
  92. GRB 251103A: NOT optical afterglow candidate
  93. GRB 251103A: SVOM detection of a bright burst
  94. GRB 251102B: Fermi GBM Final Real-time Localization
  95. Fermi GRB 251102A: Global MASTER-Net observations report
  96. GRB 251102A: Fermi GBM Final Real-time Localization
  97. GRB 251031A: Fermi GBM Observation
  98. LIGO/Virgo/KAGRA S251031cq: Identification of a GW compact binary merger candidate
  99. GRB 251031A: Swift/BAT-GUANO localization skymap of a burst
  100. Konus-Wind detection of GRB 251028A

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