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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 250926B: VZLUSAT-2 detection
  2. GRB 250926A: VZLUSAT-2 detection
  3. GRB 250925A: VZLUSAT-2 detection
  4. GRB 251026B: Fermi GBM Observation
  5. GRB 251026A/EP251026a: SVOM/VT optical counterpart
  6. GRB 251026A/EP251026a: EP-FXT follow-up observation
  7. The EP-WXT trigger 01709247588 is likely a flaring star
  8. GRB 251028B: Fermi/GBM observation
  9. GRB 251028B: Swift/BAT-GUANO localization skymap of a burst
  10. GRB 251028B: Glowbug gamma-ray detection
  11. GRB 251028A: Glowbug gamma-ray detection
  12. GRB 251028B: CALET Gamma-Ray Burst Monitor detection
  13. Fermi GRB 251028B: Global MASTER-Net observations report
  14. GRB 251025B: GROWTH-India Telescope continued multiband optical observations and rebrightening
  15. GRB 251028B: Fermi GBM Final Localization Correction
  16. GRB251026B: PRIME H-band upper limit
  17. GRB251025B: 3.6m DOT Optical Observations
  18. GRB 251028A: BALROG localization (Fermi Trigger 783314796 / GRB 251028143)
  19. GRB 251028A: MAXI/GSC detection
  20. GRB 251028A: Fermi GBM Final Real-time Localization
  21. The EP-WXT trigger 01709247525 is not a real source
  22. SVOM trigger sb25102702/GRB 251027A is not a GRB
  23. IceCube-251025A: Upper limits from a search for additional neutrino events in IceCube
  24. GRB 251025B: Swift-XRT confirmation of fading
  25. GRB 251013C : 3.4-m telescope of Iranian National Observatory (INO340) optical observations
  26. GRB 251026B: Swift-XRT observations of GOTO25jgl/AT2025absf
  27. GRB 251025C: Glowbug gamma-ray detection
  28. Fermi-LAT Gamma-ray Observations of IceCube-251025A
  29. GRB 251023B: Swift-UVOT Upper Limits
  30. Konus-Wind detection of GRB 251022A
  31. GRB 251027A: Swift-XRT observations
  32. EP251027.145: COLIBRÍ optical upper limits
  33. GRB 251022A: SVOM/GRM observation
  34. GRB 251026B: Swift ToO observations
  35. GRB 251026A/EP251026a: Einstein Probe detection of a fast X-ray transient
  36. GRB 251027A: LCO optical upper limit
  37. GRB 251027A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  38. GRB 251017A: Mondy AZT-33IK and Koshka Zeiss-1000 optical observations
  39. GRB 251023B / EP251023b: Mondy optical upper limit
  40. GRB 251017A: INASAN-Kislovodsk optical observations
  41. GRB 251026A: Mondy optical upper limit
  42. GRB 251025B: Mondy optical observations
  43. GRB 251025B: Kilonova-Catcher optical afterglow detection
  44. Konus-Wind detection of GRB 251016A (short/hard)
  45. GRB 251025B: VLT/MUSE spectroscopic redshift z = 2.003
  46. GRB 251027A: SVOM detection of a faint burst
  47. GRB 251026B: Tentative GOTO optical counterpart candidate
  48. GRB 251025C: AstroSat CZTI detection
  49. EP251023a: Mondy optical observations
  50. GRB 251025C: CALET Gamma-Ray Burst Monitor detection
  51. GRB 251025B: MAO/AZT-22 optical observations
  52. LIGO/Virgo/KAGRA S251026bn: Updated Sky localization
  53. Fermi GRB 251026B: Global MASTER-Net observations report
  54. Fermi GRB 251025C: Global MASTER-Net observations report
  55. LIGO/Virgo/KAGRA S251026bn: Identification of a GW compact binary merger candidate
  56. GRB 251026A: Swift-XRT observations
  57. GRB 251025B: OHP/T193 optical detection
  58. GRB 251025B: J-band detection with WINTER
  59. GRB 251026A: SVOM/C-GFT upper limit
  60. IceCube-251025A: DDOTI Optical Upper Limit
  61. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  62. GRB 251026B: Fermi GBM Final Localization
  63. GRB 251026A: SVOM detection of a long burst
  64. GRB 251025B: SVOM/VT optical bump
  65. GRB 251025B: SVOM/COLIBRÍ (FM-GFT) strong rebrightening of the optical counterpart
  66. GRB 251023A: SVOM/GRM observation
  67. GRB 251025B: ULL-ASTRO-MASTER optical counterpart detection with IAC80 telescope at Teide Observatory
  68. GRB 251025C: Fermi GBM Final Real-time Localization
  69. Konus-Wind detection of GRB 251016B
  70. GRB 251025B: GROWTH-India Telescope optical observations
  71. GRB 251024A: Swift/UVOT Upper Limits
  72. GRB 251025B: Swift-XRT afterglow detection
  73. GRB 251024A: Swift-BAT refined analysis
  74. IceCube Alert 251025.57: Global MASTER-Net observations report
  75. GRB 251024A: Swift-XRT refined Analysis
  76. GRB 251025A (sb25102501): stellar flare confirmed
  77. GRB 251025B: SVOM/VT optical observations with VHF data
  78. GRB 251025B: MASTER OT detection
  79. GRB 251025B: SVOM/C-GFT optical counterpart detection
  80. GRB 251025B: SVOM detection of a burst
  81. IceCube-251025A - IceCube observation of a high-energy neutrino candidate track-like event
  82. GRB 251025A (sb25102501): Likely a stellar flare by SVOM/VT
  83. GRB 251025A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  84. GRB 251025A: SVOM/VT VHF optical upper limit
  85. GRB 251025A: SVOM detection of a faint burst
  86. GRB 251003A: VLA Detection
  87. GRB 251024A: Enhanced Swift-XRT position
  88. GRB 251023C: Glowbug gamma-ray detection
  89. GRB 251024A: LCOGT Optical Afterglow Detection
  90. GRB 251022A: KAIT optical observations
  91. GRB 251024A: Swift detection of a burst
  92. Swift GRB 251024A: Global MASTER-Net observations report
  93. GRB 251023B / EP251023b: COLIBRÍ Confirmation of the Fading Nature of the Optical Candidate
  94. GRB 251022A: COLIBRÍ Further Multi-frequency Optical Observations
  95. EP251023a: MAO/AZT-22 optical observations
  96. GRB 251023B: OHP/T193 optical observations
  97. EP251023a: OHP/T193 optical observations
  98. GRB 251023C: AstroSat CZTI detection
  99. EP251023b/GRB 251023B: JinShan optical observation
  100. GRB 251022A: Swift-XRT detection of GOTO25iym

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