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

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