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

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