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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 251105A: AstroSat CZTI detection
  2. LIGO/Virgo/KAGRA S251108fi: One counterpart neutrino candidate from IceCube neutrino searches
  3. IceCube-Cascade 251107A: Upper limits from a search for additional neutrino events in IceCube
  4. LIGO/Virgo/KAGRA S251108fi: Updated Sky localization
  5. LIGO/Virgo/KAGRA S251108dn: Updated Sky localization
  6. GRB 251108A: Fermi GBM Final Localization Correction
  7. Fermi trigger No 784329591: Global MASTER-Net observations report
  8. LIGO/Virgo/KAGRA S251108fi: Identification of a GW compact binary merger candidate
  9. Fermi trigger No 784279167: Global MASTER-Net observations report
  10. SVOM GRB251108.54: Global MASTER-Net observations report
  11. GRB 251102B: SVOM/GRM observation
  12. Fermi Gamma-ray Burst Monitor trigger 784279167/251108305 is not a GRB
  13. LIGO/Virgo/KAGRA S251108dn: Identification of a GW compact binary merger candidate
  14. The EP-WXT trigger 01709248051 is likely a flaring star
  15. SVOM GRB251106.83: Global MASTER-Net observations report
  16. LIGO/Virgo/KAGRA S251105aj: Updated Sky localization
  17. LIGO/Virgo/KAGRA S251103f: Updated Sky localization
  18. IPN triangulation of GRB 251105B (possible sGRB with EE)
  19. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  20. GRB 251106B: SVOM/GRM observation of a short burst
  21. GRB 251106A: Swift-XRT afterglow detection
  22. GRB 251106A: Kilonova-Catcher optical upper limit
  23. Fermi GBM Sub-Threshold Detection of GRB 251106A
  24. GRB 251106A: Swift/BAT arcminute localization of a burst
  25. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  26. GRB 251106A: MASTER optical observations
  27. GRB 251106A: SVOM detection of a burst
  28. GRB 251103B: AstroSat CZTI detection
  29. GRB 251025C: TERI Gamma-ray detection
  30. GRB 251016B: TERI Gamma-ray detection
  31. GRB 251016A: TERI Gamma-ray detection of a short burst
  32. GRB 250920C: TERI Gamma-ray detection
  33. Fermi trigger No 784034269: Global MASTER-Net observations report
  34. Fermi Gamma-ray Burst Monitor trigger 784109140/251106337 is not a GRB
  35. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  36. GRB 251105A: Fermi GBM Observation
  37. GRB 251105C: Fermi GBM Final Localization Correction
  38. LIGO/Virgo/KAGRA S251031dw: Candidates from the Zwicky Transient Facility
  39. GRB 251105A: Swift/BAT-GUANO localization skymap of a burst
  40. GRB 251104A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  41. GRB 251105B: AstroSat CZTI detection of a short burst with extended emission
  42. GRB 251023A: SVOM/ECLAIRs detection of a burst through targeted search
  43. Fermi GBM Sub-Threshold Detection of GRB 251105B
  44. GRB 251103B: Swift/UVOT Upper Limits
  45. LIGO/Virgo/KAGRA S251105aj: Identification of a GW compact binary merger candidate
  46. GRB 251105B: SVOM/GRM observation of a possible short burst with extended emission
  47. Fermi GRB 251105A: Global MASTER-Net observations report
  48. GRB 251105A: Fermi GBM Final Real-time Localization
  49. Fermi Gamma-ray Burst Monitor trigger 783986701/251104920 is not a GRB
  50. GRB 251103B: Fermi GBM observation
  51. GRB 251104A: SVOM detection of a burst
  52. GRB 251028A: Insight-HXMT/HE detection
  53. GRB 251103A: Optical afterglow detection by ZTF’s public survey
  54. EP251102a: FTW optical and NIR observations
  55. GRB 251103A: WFST optical observations
  56. EP251102a: update of EP-FXT follow-up observation
  57. EP251102a: OHP/T193 optical observations
  58. GRB 251103A: OHP/T193 optical observations
  59. GRB 251103A: Xinglong 2.16m optical detection
  60. GRB 251103A: Insight-HXMT detection
  61. GRB 251103A: KAIT optical observations
  62. GRB 251103B: Nanshan/HMT optical upper limit
  63. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  64. GRB 251103A: Swift/BAT-GUANO arcminute localization of a burst
  65. GRB 251103B: MITSuME Akeno optical upper limits
  66. GRB 251103B: Swift-XRT refined Analysis
  67. Fermi GRB 251103A: Global MASTER-Net observations report
  68. LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate
  69. EP251102a: NIR observations with WINTER
  70. GRB 251103A: J-band detection with WINTER
  71. Swift GRB 251103B: Global MASTER-Net observations report
  72. GRB 251103B: GROWTH-India Telescope optical upper limits
  73. GRB 251103A: Kilonova-Catcher optical afterglow detection
  74. GRB 251103B: Enhanced Swift-XRT position
  75. GRB 251103B: Prompt enhanced Swift-XRT position
  76. GRB 251103B: Swift detection of a burst
  77. GRB 251103B: Fermi GBM Final Real-time Localization
  78. GRB 251103A: Swift/UVOT Detection
  79. GRB 251103A: Fermi GBM Observation
  80. GRB 251103A: SVOM/GRM observation
  81. GRB 251103A: Swift-XRT afterglow detection
  82. LIGO/Virgo/KAGRA S251031cq: Updated Sky localization
  83. GRB 251103A: SVOM/COLIBRÍ (FM-GFT) optical observations
  84. EP251102a: Einstein Probe detection of a fast X-ray transient
  85. GRB 251025B: OHP/T193 optical upper limit
  86. EP251102a (WXT 11900459650): LCO observations confirm COLIBRÍ candidate
  87. GRB 251103A: LCO optical observation
  88. EP251102.890: COLIBRÍ optical counterpart candidate
  89. GRB 251103A: GOTO optical afterglow detection
  90. GRB 251102A: AstroSat CZTI detection
  91. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical counterpart
  92. GRB 251103A: NOT spectroscopic redshift z = 0.76
  93. GRB 251103A: BOOTES-2/TELMA optical afterglow
  94. GRB 251103A: LCO optical afterglow detection
  95. GRB 251103A: NOT optical afterglow candidate (duplicate submission)
  96. GRB 251103A: Fermi GBM Final Localization
  97. GRB 251103A: NOT optical afterglow candidate
  98. GRB 251103A: SVOM detection of a bright burst
  99. GRB 251102B: Fermi GBM Final Real-time Localization
  100. Fermi GRB 251102A: Global MASTER-Net observations report

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