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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 251022A: COLIBRÍ optical observations
  2. GRB 251013C: ISON-Castelgrande observatory optical observations
  3. GRB 251022A: MASTER OT detection
  4. GRB 251022A: DDOTI Optical Detection
  5. EP251021b/GRB 251021A: SVOM/VT optical candidate
  6. GRB 251023B / MAXI J0451+122: MAXI/GSC detection
  7. EP251023a: NOT optical counterpart detection
  8. Fermi GRB 251023A: Global MASTER-Net observations report
  9. EP251023a: GSP Optical Counterpart Detection
  10. EP251023a: Einstein Probe detection of an X-ray transient
  11. EP/WXT 01709247295: GOTO optical afterglow candidate.
  12. GRB 251022A: GOTO optical counterpart detection
  13. GRB 251023A: Fermi GBM Final Localization Correction
  14. GRB 251022A: Fermi-LAT detection
  15. GRB 251016B: Fermi GBM Detection
  16. GRB 251022A: Tiled Swift observations
  17. LAT GRB251022A: Global MASTER-Net observations report
  18. GRB 251022A: Fermi GBM Final Real-time Localization
  19. GRB 251021A/EP251021b: Fermi-GBM Sub-Threshold Detection
  20. EP251021b: BOOTES-7 optical upper limit
  21. EP251021b: Einstein Probe detection of a fast X-ray transient
  22. GRB 250911A: MAXI/GSC detection
  23. LIGO/Virgo/KAGRA S251021u: Updated Sky localization
  24. GRB 251016A: SVOM/ECLAIRs refined analysis
  25. LIGO/Virgo/KAGRA S251021u: Identification of a GW compact binary merger candidate
  26. LIGO/Virgo/KAGRA S251018bi: Updated Sky localization
  27. Fermi-LAT gamma-ray observations of IceCube-251018A
  28. GRB 251017A : RAPAS follow-up observations
  29. IceCube-251018A: Upper limits from a search for additional neutrino events in IceCube
  30. GRB 251017A: COLIBRÍ optical observations of a late plateau
  31. IceCube-251018A: DDOTI Optical Upper Limit
  32. GRB 251017A: Swift-BAT refined analysis
  33. GRB 251016A: Fermi GBM Observation
  34. GRB 251018A: Fermi GBM Observation
  35. GRB 251018A: BOOTES-5 and BOOTES-7 early optical detections
  36. GRB 251018A: Swift-XRT refined Analysis
  37. GRB 251018A: Enhanced Swift-XRT position
  38. Fermi trigger No 782500909: Global MASTER-Net observations report
  39. GRB 251016A: HXMT/HE detection
  40. IceCube-251018A: Global MASTER-Net observations report
  41. LIGO/Virgo/KAGRA S251018bi: Identification of a GW compact binary merger candidate
  42. GRB 251016A: Swift-XRT afterglow detection
  43. GRB 251017A: Swift/UVOT Detection
  44. GRB 251016A: Swift/UVOT Detection
  45. GRB 251018A: Swift/UVOT Detection
  46. IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event
  47. IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event (duplicate submission)
  48. GRB 251017A: VLT/MUSE spectroscopic redshift z = 4.327
  49. GRB 251016A: VLT/FORS2 Optical Observation
  50. GRB 251017A: COLIBRÍ photometric redshift
  51. GRB 251017A: Swift-XRT refined Analysis
  52. GRB 251018A: MASTER OT detection
  53. GRB 251018A: TRT optical afterglow detection
  54. Swift GRB 251018A: Global MASTER-Net observations report
  55. GRB 251018A: Swift detection of a burst with an optical counterpart
  56. GRB 251018A: Fermi GBM Final Real-time Localization
  57. GRB 251017A: SVOM/VT optical observation
  58. GRB 251011A: Fermi GBM Observation
  59. GRB 251017A: OHP/T193 i-band observations
  60. GRB 251013C: OHP/T193 third epoch optical observations and detected rebrightening
  61. LIGO/Virgo/KAGRA S251017di: Retraction of GW compact binary merger candidate
  62. GRB 251017A: J-band detection with WINTER
  63. GRB 251017A: Glowbug gamma-ray detection
  64. GRB 251013C: Liverpool Telescope observations
  65. GRB 251013C: Leavitt Observatory optical photometry
  66. Fermi GRB 251016B: Global MASTER-Net observations report
  67. GRB 251017A: JinShan observations of the optical afterglow
  68. Swift GRB 251017A: Global MASTER-Net observations report
  69. GRB 251017A : MITSuME Akeno optical afterglow candidate detection
  70. Swift Trigger 1404295 is not a GRB
  71. GRB 251016A: AstroSat CZTI detection of a short burst
  72. GRB 251017A: Enhanced Swift-XRT position
  73. GRB 251017A: COLIBRÍ Early Afterglow Detection
  74. GRB 251016B: AstroSat CZTI detection
  75. GRB 251017A: BOOTES-5/JGT early optical afterglow detection
  76. GRB 251017A: Swift detection of a burst with an optical counterpart
  77. GRB 251016A: CALET Gamma-Ray Burst Monitor detection
  78. GRB 251016B: CALET Gamma-Ray Burst Monitor detection
  79. GRB 251013C: JinShan observations of the non-thermal rebrightening of the optical counterpart
  80. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) observations of a strong and late rebrightening of the optical counterpart
  81. GRB 251007B: Swift-BAT refined analysis
  82. GRB 251016B: Fermi GBM Final Real-time Localization
  83. GRB 251014D: Swift-BAT refined analysis
  84. GRB 251016A: BOOTES-6/DPRT optical upper limit
  85. GRB 251016A: Glowbug gamma-ray detection of a short burst
  86. GRB 251013C: VLA detection
  87. sb25101602: Swift-XRT counterpart detection
  88. Fermi GRB 251016A: Global MASTER-Net observations report
  89. GRB 251016A: Fermi GBM Final Localization
  90. GRB 251016A: SVOM detection of a short burst
  91. GRB 251014A: Swift-XRT observations
  92. LIGO/Virgo/KAGRA S251014cn: Updated Sky localization
  93. GRB 251014B: PRIME J-band upper limit
  94. Upper limits from a search for additional neutrino events in IceCube
  95. IceCube Alert 251014.77: Global MASTER-Net observations report
  96. Swift GRB251015.60: Global MASTER-Net observations report
  97. GRB 251013C: Kilonova-Catcher optical afterglow detection
  98. Fermi-LAT Gamma-ray Observations of IceCube-251014A
  99. GRB 251013D: Swift/UVOT Observations
  100. GRB 251013C: Swift/UVOT Detection

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