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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 251103A: NOT optical afterglow candidate (duplicate submission)
  2. GRB 251103A: Fermi GBM Final Localization
  3. GRB 251103A: NOT optical afterglow candidate
  4. GRB 251103A: SVOM detection of a bright burst
  5. GRB 251102B: Fermi GBM Final Real-time Localization
  6. Fermi GRB 251102A: Global MASTER-Net observations report
  7. GRB 251102A: Fermi GBM Final Real-time Localization
  8. GRB 251031A: Fermi GBM Observation
  9. LIGO/Virgo/KAGRA S251031cq: Identification of a GW compact binary merger candidate
  10. GRB 251031A: Swift/BAT-GUANO localization skymap of a burst
  11. Konus-Wind detection of GRB 251028A
  12. GRB 251031A: BALROG localization (Fermi Trigger 783588065 / GRB 251031306)
  13. GRB 251031A: Fermi GBM Final Real-time Localization
  14. GRB 251025C: SVOM/GRM observation
  15. GRB 251028A: GECAM-B detection
  16. GRB 251028A: SVOM/GRM observation
  17. IceCube-251025A: Two Transient Candidates from the Zwicky Transient Facility
  18. GRB 251028A: Fermi GBM Observation
  19. GRB 251026B: SOAR Classification of GOTO25jgl/SN2025absf as a Type Ia supernova
  20. GRB 251022A: Swift-XRT confirmation of fading
  21. GRB 251026B: LBT near-infrared observations
  22. GRB 250926B: VZLUSAT-2 detection
  23. GRB 250926A: VZLUSAT-2 detection
  24. GRB 250925A: VZLUSAT-2 detection
  25. GRB 251026B: Fermi GBM Observation
  26. GRB 251026A/EP251026a: SVOM/VT optical counterpart
  27. GRB 251026A/EP251026a: EP-FXT follow-up observation
  28. The EP-WXT trigger 01709247588 is likely a flaring star
  29. GRB 251028B: Fermi/GBM observation
  30. GRB 251028B: Swift/BAT-GUANO localization skymap of a burst
  31. GRB 251028B: Glowbug gamma-ray detection
  32. GRB 251028A: Glowbug gamma-ray detection
  33. GRB 251028B: CALET Gamma-Ray Burst Monitor detection
  34. Fermi GRB 251028B: Global MASTER-Net observations report
  35. GRB 251025B: GROWTH-India Telescope continued multiband optical observations and rebrightening
  36. GRB 251028B: Fermi GBM Final Localization Correction
  37. GRB251026B: PRIME H-band upper limit
  38. GRB251025B: 3.6m DOT Optical Observations
  39. GRB 251028A: BALROG localization (Fermi Trigger 783314796 / GRB 251028143)
  40. GRB 251028A: MAXI/GSC detection
  41. GRB 251028A: Fermi GBM Final Real-time Localization
  42. The EP-WXT trigger 01709247525 is not a real source
  43. SVOM trigger sb25102702/GRB 251027A is not a GRB
  44. IceCube-251025A: Upper limits from a search for additional neutrino events in IceCube
  45. GRB 251025B: Swift-XRT confirmation of fading
  46. GRB 251013C : 3.4-m telescope of Iranian National Observatory (INO340) optical observations
  47. GRB 251026B: Swift-XRT observations of GOTO25jgl/AT2025absf
  48. GRB 251025C: Glowbug gamma-ray detection
  49. Fermi-LAT Gamma-ray Observations of IceCube-251025A
  50. GRB 251023B: Swift-UVOT Upper Limits
  51. Konus-Wind detection of GRB 251022A
  52. GRB 251027A: Swift-XRT observations
  53. EP251027.145: COLIBRÍ optical upper limits
  54. GRB 251022A: SVOM/GRM observation
  55. GRB 251026B: Swift ToO observations
  56. GRB 251026A/EP251026a: Einstein Probe detection of a fast X-ray transient
  57. GRB 251027A: LCO optical upper limit
  58. GRB 251027A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  59. GRB 251017A: Mondy AZT-33IK and Koshka Zeiss-1000 optical observations
  60. GRB 251023B / EP251023b: Mondy optical upper limit
  61. GRB 251017A: INASAN-Kislovodsk optical observations
  62. GRB 251026A: Mondy optical upper limit
  63. GRB 251025B: Mondy optical observations
  64. GRB 251025B: Kilonova-Catcher optical afterglow detection
  65. Konus-Wind detection of GRB 251016A (short/hard)
  66. GRB 251025B: VLT/MUSE spectroscopic redshift z = 2.003
  67. GRB 251027A: SVOM detection of a faint burst
  68. GRB 251026B: Tentative GOTO optical counterpart candidate
  69. GRB 251025C: AstroSat CZTI detection
  70. EP251023a: Mondy optical observations
  71. GRB 251025C: CALET Gamma-Ray Burst Monitor detection
  72. GRB 251025B: MAO/AZT-22 optical observations
  73. LIGO/Virgo/KAGRA S251026bn: Updated Sky localization
  74. Fermi GRB 251026B: Global MASTER-Net observations report
  75. Fermi GRB 251025C: Global MASTER-Net observations report
  76. LIGO/Virgo/KAGRA S251026bn: Identification of a GW compact binary merger candidate
  77. GRB 251026A: Swift-XRT observations
  78. GRB 251025B: OHP/T193 optical detection
  79. GRB 251025B: J-band detection with WINTER
  80. GRB 251026A: SVOM/C-GFT upper limit
  81. IceCube-251025A: DDOTI Optical Upper Limit
  82. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  83. GRB 251026B: Fermi GBM Final Localization
  84. GRB 251026A: SVOM detection of a long burst
  85. GRB 251025B: SVOM/VT optical bump
  86. GRB 251025B: SVOM/COLIBRÍ (FM-GFT) strong rebrightening of the optical counterpart
  87. GRB 251023A: SVOM/GRM observation
  88. GRB 251025B: ULL-ASTRO-MASTER optical counterpart detection with IAC80 telescope at Teide Observatory
  89. GRB 251025C: Fermi GBM Final Real-time Localization
  90. Konus-Wind detection of GRB 251016B
  91. GRB 251025B: GROWTH-India Telescope optical observations
  92. GRB 251024A: Swift/UVOT Upper Limits
  93. GRB 251025B: Swift-XRT afterglow detection
  94. GRB 251024A: Swift-BAT refined analysis
  95. IceCube Alert 251025.57: Global MASTER-Net observations report
  96. GRB 251024A: Swift-XRT refined Analysis
  97. GRB 251025A (sb25102501): stellar flare confirmed
  98. GRB 251025B: SVOM/VT optical observations with VHF data
  99. GRB 251025B: MASTER OT detection
  100. GRB 251025B: SVOM/C-GFT optical counterpart detection

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