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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 251025B: SVOM/C-GFT optical counterpart detection
  2. GRB 251025B: SVOM detection of a burst
  3. IceCube-251025A - IceCube observation of a high-energy neutrino candidate track-like event
  4. GRB 251025A (sb25102501): Likely a stellar flare by SVOM/VT
  5. GRB 251025A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  6. GRB 251025A: SVOM/VT VHF optical upper limit
  7. GRB 251025A: SVOM detection of a faint burst
  8. GRB 251003A: VLA Detection
  9. GRB 251024A: Enhanced Swift-XRT position
  10. GRB 251023C: Glowbug gamma-ray detection
  11. GRB 251024A: LCOGT Optical Afterglow Detection
  12. GRB 251022A: KAIT optical observations
  13. GRB 251024A: Swift detection of a burst
  14. Swift GRB 251024A: Global MASTER-Net observations report
  15. GRB 251023B / EP251023b: COLIBRÍ Confirmation of the Fading Nature of the Optical Candidate
  16. GRB 251022A: COLIBRÍ Further Multi-frequency Optical Observations
  17. EP251023a: MAO/AZT-22 optical observations
  18. GRB 251023B: OHP/T193 optical observations
  19. EP251023a: OHP/T193 optical observations
  20. GRB 251023C: AstroSat CZTI detection
  21. EP251023b/GRB 251023B: JinShan optical observation
  22. GRB 251022A: Swift-XRT detection of GOTO25iym
  23. EP251023b: Global MASTER-Net observations report
  24. EP251023b/GRB 251023B : Einstein Probe detection of a fast X-ray transient
  25. GRB 251023C: CALET Gamma-Ray Burst Monitor detection
  26. GRB 251022A: GROWTH-India Telescope optical observations
  27. GRB 251023C: Swift/BAT-GUANO localization skymap of a burst
  28. EP251023a: GROWTH-India Telescope optical observations
  29. GRB 251022A: Fermi GBM Observation
  30. GRB 251022A: Swift/BAT-GUANO localization skymap of a burst
  31. GRB 251023A: Glowbug gamma-ray detection
  32. GRB 251023B: Glowbug gamma-ray detection
  33. EP251023a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm telescope at Teide Observatory
  34. EP251023a: Global MASTER-Net observations report
  35. GRB 251023B / EP#01709247298: COLIBRÍ optical counterpart candidate
  36. IPN triangulation of GRB 251016B
  37. GRB 251023B: CALET Gamma-Ray Burst Monitor detection
  38. EP#01709247298: Swift-XRT counterpart detection
  39. EP251023a: COLIBRÍ optical observations
  40. GRB 251013C: further SAO RAS optical observations
  41. EP251023a: Keck/LRIS spectroscopic redshift z=2.232
  42. GRB 251022A: COLIBRÍ optical observations
  43. GRB 251013C: ISON-Castelgrande observatory optical observations
  44. GRB 251022A: MASTER OT detection
  45. GRB 251022A: DDOTI Optical Detection
  46. EP251021b/GRB 251021A: SVOM/VT optical candidate
  47. GRB 251023B / MAXI J0451+122: MAXI/GSC detection
  48. EP251023a: NOT optical counterpart detection
  49. Fermi GRB 251023A: Global MASTER-Net observations report
  50. EP251023a: GSP Optical Counterpart Detection
  51. EP251023a: Einstein Probe detection of an X-ray transient
  52. EP/WXT 01709247295: GOTO optical afterglow candidate.
  53. GRB 251022A: GOTO optical counterpart detection
  54. GRB 251023A: Fermi GBM Final Localization Correction
  55. GRB 251022A: Fermi-LAT detection
  56. GRB 251016B: Fermi GBM Detection
  57. GRB 251022A: Tiled Swift observations
  58. LAT GRB251022A: Global MASTER-Net observations report
  59. GRB 251022A: Fermi GBM Final Real-time Localization
  60. GRB 251021A/EP251021b: Fermi-GBM Sub-Threshold Detection
  61. EP251021b: BOOTES-7 optical upper limit
  62. EP251021b: Einstein Probe detection of a fast X-ray transient
  63. GRB 250911A: MAXI/GSC detection
  64. LIGO/Virgo/KAGRA S251021u: Updated Sky localization
  65. GRB 251016A: SVOM/ECLAIRs refined analysis
  66. LIGO/Virgo/KAGRA S251021u: Identification of a GW compact binary merger candidate
  67. LIGO/Virgo/KAGRA S251018bi: Updated Sky localization
  68. Fermi-LAT gamma-ray observations of IceCube-251018A
  69. GRB 251017A : RAPAS follow-up observations
  70. IceCube-251018A: Upper limits from a search for additional neutrino events in IceCube
  71. GRB 251017A: COLIBRÍ optical observations of a late plateau
  72. IceCube-251018A: DDOTI Optical Upper Limit
  73. GRB 251017A: Swift-BAT refined analysis
  74. GRB 251016A: Fermi GBM Observation
  75. GRB 251018A: Fermi GBM Observation
  76. GRB 251018A: BOOTES-5 and BOOTES-7 early optical detections
  77. GRB 251018A: Swift-XRT refined Analysis
  78. GRB 251018A: Enhanced Swift-XRT position
  79. Fermi trigger No 782500909: Global MASTER-Net observations report
  80. GRB 251016A: HXMT/HE detection
  81. IceCube-251018A: Global MASTER-Net observations report
  82. LIGO/Virgo/KAGRA S251018bi: Identification of a GW compact binary merger candidate
  83. GRB 251016A: Swift-XRT afterglow detection
  84. GRB 251017A: Swift/UVOT Detection
  85. GRB 251016A: Swift/UVOT Detection
  86. GRB 251018A: Swift/UVOT Detection
  87. IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event
  88. IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event (duplicate submission)
  89. GRB 251017A: VLT/MUSE spectroscopic redshift z = 4.327
  90. GRB 251016A: VLT/FORS2 Optical Observation
  91. GRB 251017A: COLIBRÍ photometric redshift
  92. GRB 251017A: Swift-XRT refined Analysis
  93. GRB 251018A: MASTER OT detection
  94. GRB 251018A: TRT optical afterglow detection
  95. Swift GRB 251018A: Global MASTER-Net observations report
  96. GRB 251018A: Swift detection of a burst with an optical counterpart
  97. GRB 251018A: Fermi GBM Final Real-time Localization
  98. GRB 251017A: SVOM/VT optical observation
  99. GRB 251011A: Fermi GBM Observation
  100. GRB 251017A: OHP/T193 i-band observations

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