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

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