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

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