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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. IceCube-251025A: Two Transient Candidates from the Zwicky Transient Facility
  2. GRB 251028A: Fermi GBM Observation
  3. GRB 251026B: SOAR Classification of GOTO25jgl/SN2025absf as a Type Ia supernova
  4. GRB 251022A: Swift-XRT confirmation of fading
  5. GRB 251026B: LBT near-infrared observations
  6. GRB 250926B: VZLUSAT-2 detection
  7. GRB 250926A: VZLUSAT-2 detection
  8. GRB 250925A: VZLUSAT-2 detection
  9. GRB 251026B: Fermi GBM Observation
  10. GRB 251026A/EP251026a: SVOM/VT optical counterpart
  11. GRB 251026A/EP251026a: EP-FXT follow-up observation
  12. The EP-WXT trigger 01709247588 is likely a flaring star
  13. GRB 251028B: Fermi/GBM observation
  14. GRB 251028B: Swift/BAT-GUANO localization skymap of a burst
  15. GRB 251028B: Glowbug gamma-ray detection
  16. GRB 251028A: Glowbug gamma-ray detection
  17. GRB 251028B: CALET Gamma-Ray Burst Monitor detection
  18. Fermi GRB 251028B: Global MASTER-Net observations report
  19. GRB 251025B: GROWTH-India Telescope continued multiband optical observations and rebrightening
  20. GRB 251028B: Fermi GBM Final Localization Correction
  21. GRB251026B: PRIME H-band upper limit
  22. GRB251025B: 3.6m DOT Optical Observations
  23. GRB 251028A: BALROG localization (Fermi Trigger 783314796 / GRB 251028143)
  24. GRB 251028A: MAXI/GSC detection
  25. GRB 251028A: Fermi GBM Final Real-time Localization
  26. The EP-WXT trigger 01709247525 is not a real source
  27. SVOM trigger sb25102702/GRB 251027A is not a GRB
  28. IceCube-251025A: Upper limits from a search for additional neutrino events in IceCube
  29. GRB 251025B: Swift-XRT confirmation of fading
  30. GRB 251013C : 3.4-m telescope of Iranian National Observatory (INO340) optical observations
  31. GRB 251026B: Swift-XRT observations of GOTO25jgl/AT2025absf
  32. GRB 251025C: Glowbug gamma-ray detection
  33. Fermi-LAT Gamma-ray Observations of IceCube-251025A
  34. GRB 251023B: Swift-UVOT Upper Limits
  35. Konus-Wind detection of GRB 251022A
  36. GRB 251027A: Swift-XRT observations
  37. EP251027.145: COLIBRÍ optical upper limits
  38. GRB 251022A: SVOM/GRM observation
  39. GRB 251026B: Swift ToO observations
  40. GRB 251026A/EP251026a: Einstein Probe detection of a fast X-ray transient
  41. GRB 251027A: LCO optical upper limit
  42. GRB 251027A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  43. GRB 251017A: Mondy AZT-33IK and Koshka Zeiss-1000 optical observations
  44. GRB 251023B / EP251023b: Mondy optical upper limit
  45. GRB 251017A: INASAN-Kislovodsk optical observations
  46. GRB 251026A: Mondy optical upper limit
  47. GRB 251025B: Mondy optical observations
  48. GRB 251025B: Kilonova-Catcher optical afterglow detection
  49. Konus-Wind detection of GRB 251016A (short/hard)
  50. GRB 251025B: VLT/MUSE spectroscopic redshift z = 2.003
  51. GRB 251027A: SVOM detection of a faint burst
  52. GRB 251026B: Tentative GOTO optical counterpart candidate
  53. GRB 251025C: AstroSat CZTI detection
  54. EP251023a: Mondy optical observations
  55. GRB 251025C: CALET Gamma-Ray Burst Monitor detection
  56. GRB 251025B: MAO/AZT-22 optical observations
  57. LIGO/Virgo/KAGRA S251026bn: Updated Sky localization
  58. Fermi GRB 251026B: Global MASTER-Net observations report
  59. Fermi GRB 251025C: Global MASTER-Net observations report
  60. LIGO/Virgo/KAGRA S251026bn: Identification of a GW compact binary merger candidate
  61. GRB 251026A: Swift-XRT observations
  62. GRB 251025B: OHP/T193 optical detection
  63. GRB 251025B: J-band detection with WINTER
  64. GRB 251026A: SVOM/C-GFT upper limit
  65. IceCube-251025A: DDOTI Optical Upper Limit
  66. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  67. GRB 251026B: Fermi GBM Final Localization
  68. GRB 251026A: SVOM detection of a long burst
  69. GRB 251025B: SVOM/VT optical bump
  70. GRB 251025B: SVOM/COLIBRÍ (FM-GFT) strong rebrightening of the optical counterpart
  71. GRB 251023A: SVOM/GRM observation
  72. GRB 251025B: ULL-ASTRO-MASTER optical counterpart detection with IAC80 telescope at Teide Observatory
  73. GRB 251025C: Fermi GBM Final Real-time Localization
  74. Konus-Wind detection of GRB 251016B
  75. GRB 251025B: GROWTH-India Telescope optical observations
  76. GRB 251024A: Swift/UVOT Upper Limits
  77. GRB 251025B: Swift-XRT afterglow detection
  78. GRB 251024A: Swift-BAT refined analysis
  79. IceCube Alert 251025.57: Global MASTER-Net observations report
  80. GRB 251024A: Swift-XRT refined Analysis
  81. GRB 251025A (sb25102501): stellar flare confirmed
  82. GRB 251025B: SVOM/VT optical observations with VHF data
  83. GRB 251025B: MASTER OT detection
  84. GRB 251025B: SVOM/C-GFT optical counterpart detection
  85. GRB 251025B: SVOM detection of a burst
  86. IceCube-251025A - IceCube observation of a high-energy neutrino candidate track-like event
  87. GRB 251025A (sb25102501): Likely a stellar flare by SVOM/VT
  88. GRB 251025A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  89. GRB 251025A: SVOM/VT VHF optical upper limit
  90. GRB 251025A: SVOM detection of a faint burst
  91. GRB 251003A: VLA Detection
  92. GRB 251024A: Enhanced Swift-XRT position
  93. GRB 251023C: Glowbug gamma-ray detection
  94. GRB 251024A: LCOGT Optical Afterglow Detection
  95. GRB 251022A: KAIT optical observations
  96. GRB 251024A: Swift detection of a burst
  97. Swift GRB 251024A: Global MASTER-Net observations report
  98. GRB 251023B / EP251023b: COLIBRÍ Confirmation of the Fading Nature of the Optical Candidate
  99. GRB 251022A: COLIBRÍ Further Multi-frequency Optical Observations
  100. EP251023a: MAO/AZT-22 optical observations

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