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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. Fermi GRB 251023A: Global MASTER-Net observations report
  2. EP251023a: GSP Optical Counterpart Detection
  3. EP251023a: Einstein Probe detection of an X-ray transient
  4. EP/WXT 01709247295: GOTO optical afterglow candidate.
  5. GRB 251022A: GOTO optical counterpart detection
  6. GRB 251023A: Fermi GBM Final Localization Correction
  7. GRB 251022A: Fermi-LAT detection
  8. GRB 251016B: Fermi GBM Detection
  9. GRB 251022A: Tiled Swift observations
  10. LAT GRB251022A: Global MASTER-Net observations report
  11. GRB 251022A: Fermi GBM Final Real-time Localization
  12. GRB 251021A/EP251021b: Fermi-GBM Sub-Threshold Detection
  13. EP251021b: BOOTES-7 optical upper limit
  14. EP251021b: Einstein Probe detection of a fast X-ray transient
  15. GRB 250911A: MAXI/GSC detection
  16. LIGO/Virgo/KAGRA S251021u: Updated Sky localization
  17. GRB 251016A: SVOM/ECLAIRs refined analysis
  18. LIGO/Virgo/KAGRA S251021u: Identification of a GW compact binary merger candidate
  19. LIGO/Virgo/KAGRA S251018bi: Updated Sky localization
  20. Fermi-LAT gamma-ray observations of IceCube-251018A
  21. GRB 251017A : RAPAS follow-up observations
  22. IceCube-251018A: Upper limits from a search for additional neutrino events in IceCube
  23. GRB 251017A: COLIBRÍ optical observations of a late plateau
  24. IceCube-251018A: DDOTI Optical Upper Limit
  25. GRB 251017A: Swift-BAT refined analysis
  26. GRB 251016A: Fermi GBM Observation
  27. GRB 251018A: Fermi GBM Observation
  28. GRB 251018A: BOOTES-5 and BOOTES-7 early optical detections
  29. GRB 251018A: Swift-XRT refined Analysis
  30. GRB 251018A: Enhanced Swift-XRT position
  31. Fermi trigger No 782500909: Global MASTER-Net observations report
  32. GRB 251016A: HXMT/HE detection
  33. IceCube-251018A: Global MASTER-Net observations report
  34. LIGO/Virgo/KAGRA S251018bi: Identification of a GW compact binary merger candidate
  35. GRB 251016A: Swift-XRT afterglow detection
  36. GRB 251017A: Swift/UVOT Detection
  37. GRB 251016A: Swift/UVOT Detection
  38. GRB 251018A: Swift/UVOT Detection
  39. IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event
  40. IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event (duplicate submission)
  41. GRB 251017A: VLT/MUSE spectroscopic redshift z = 4.327
  42. GRB 251016A: VLT/FORS2 Optical Observation
  43. GRB 251017A: COLIBRÍ photometric redshift
  44. GRB 251017A: Swift-XRT refined Analysis
  45. GRB 251018A: MASTER OT detection
  46. GRB 251018A: TRT optical afterglow detection
  47. Swift GRB 251018A: Global MASTER-Net observations report
  48. GRB 251018A: Swift detection of a burst with an optical counterpart
  49. GRB 251018A: Fermi GBM Final Real-time Localization
  50. GRB 251017A: SVOM/VT optical observation
  51. GRB 251011A: Fermi GBM Observation
  52. GRB 251017A: OHP/T193 i-band observations
  53. GRB 251013C: OHP/T193 third epoch optical observations and detected rebrightening
  54. LIGO/Virgo/KAGRA S251017di: Retraction of GW compact binary merger candidate
  55. GRB 251017A: J-band detection with WINTER
  56. GRB 251017A: Glowbug gamma-ray detection
  57. GRB 251013C: Liverpool Telescope observations
  58. GRB 251013C: Leavitt Observatory optical photometry
  59. Fermi GRB 251016B: Global MASTER-Net observations report
  60. GRB 251017A: JinShan observations of the optical afterglow
  61. Swift GRB 251017A: Global MASTER-Net observations report
  62. GRB 251017A : MITSuME Akeno optical afterglow candidate detection
  63. Swift Trigger 1404295 is not a GRB
  64. GRB 251016A: AstroSat CZTI detection of a short burst
  65. GRB 251017A: Enhanced Swift-XRT position
  66. GRB 251017A: COLIBRÍ Early Afterglow Detection
  67. GRB 251016B: AstroSat CZTI detection
  68. GRB 251017A: BOOTES-5/JGT early optical afterglow detection
  69. GRB 251017A: Swift detection of a burst with an optical counterpart
  70. GRB 251016A: CALET Gamma-Ray Burst Monitor detection
  71. GRB 251016B: CALET Gamma-Ray Burst Monitor detection
  72. GRB 251013C: JinShan observations of the non-thermal rebrightening of the optical counterpart
  73. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) observations of a strong and late rebrightening of the optical counterpart
  74. GRB 251007B: Swift-BAT refined analysis
  75. GRB 251016B: Fermi GBM Final Real-time Localization
  76. GRB 251014D: Swift-BAT refined analysis
  77. GRB 251016A: BOOTES-6/DPRT optical upper limit
  78. GRB 251016A: Glowbug gamma-ray detection of a short burst
  79. GRB 251013C: VLA detection
  80. sb25101602: Swift-XRT counterpart detection
  81. Fermi GRB 251016A: Global MASTER-Net observations report
  82. GRB 251016A: Fermi GBM Final Localization
  83. GRB 251016A: SVOM detection of a short burst
  84. GRB 251014A: Swift-XRT observations
  85. LIGO/Virgo/KAGRA S251014cn: Updated Sky localization
  86. GRB 251014B: PRIME J-band upper limit
  87. Upper limits from a search for additional neutrino events in IceCube
  88. IceCube Alert 251014.77: Global MASTER-Net observations report
  89. Swift GRB251015.60: Global MASTER-Net observations report
  90. GRB 251013C: Kilonova-Catcher optical afterglow detection
  91. Fermi-LAT Gamma-ray Observations of IceCube-251014A
  92. GRB 251013D: Swift/UVOT Observations
  93. GRB 251013C: Swift/UVOT Detection
  94. Konus-Wind detection of GRB 251007A
  95. Fermi Gamma-ray Burst Monitor trigger 782237334/251015673 is not a GRB
  96. GRB 251013C, GCN Circular 42267, errata corrige
  97. GRB 251013C: detection of a radio counterpart at 15.5GHz
  98. GRB 251015A: Fermi GBM Final Real-time Localization
  99. GRB 251013C: SVOM/ECLAIRs refined analysis
  100. GRB 251013D: Swift-XRT observations

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