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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 251023C: CALET Gamma-Ray Burst Monitor detection
  2. GRB 251022A: GROWTH-India Telescope optical observations
  3. GRB 251023C: Swift/BAT-GUANO localization skymap of a burst
  4. EP251023a: GROWTH-India Telescope optical observations
  5. GRB 251022A: Fermi GBM Observation
  6. GRB 251022A: Swift/BAT-GUANO localization skymap of a burst
  7. GRB 251023A: Glowbug gamma-ray detection
  8. GRB 251023B: Glowbug gamma-ray detection
  9. EP251023a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm telescope at Teide Observatory
  10. EP251023a: Global MASTER-Net observations report
  11. GRB 251023B / EP#01709247298: COLIBRÍ optical counterpart candidate
  12. IPN triangulation of GRB 251016B
  13. GRB 251023B: CALET Gamma-Ray Burst Monitor detection
  14. EP#01709247298: Swift-XRT counterpart detection
  15. EP251023a: COLIBRÍ optical observations
  16. GRB 251013C: further SAO RAS optical observations
  17. EP251023a: Keck/LRIS spectroscopic redshift z=2.232
  18. GRB 251022A: COLIBRÍ optical observations
  19. GRB 251013C: ISON-Castelgrande observatory optical observations
  20. GRB 251022A: MASTER OT detection
  21. GRB 251022A: DDOTI Optical Detection
  22. EP251021b/GRB 251021A: SVOM/VT optical candidate
  23. GRB 251023B / MAXI J0451+122: MAXI/GSC detection
  24. EP251023a: NOT optical counterpart detection
  25. Fermi GRB 251023A: Global MASTER-Net observations report
  26. EP251023a: GSP Optical Counterpart Detection
  27. EP251023a: Einstein Probe detection of an X-ray transient
  28. EP/WXT 01709247295: GOTO optical afterglow candidate.
  29. GRB 251022A: GOTO optical counterpart detection
  30. GRB 251023A: Fermi GBM Final Localization Correction
  31. GRB 251022A: Fermi-LAT detection
  32. GRB 251016B: Fermi GBM Detection
  33. GRB 251022A: Tiled Swift observations
  34. LAT GRB251022A: Global MASTER-Net observations report
  35. GRB 251022A: Fermi GBM Final Real-time Localization
  36. GRB 251021A/EP251021b: Fermi-GBM Sub-Threshold Detection
  37. EP251021b: BOOTES-7 optical upper limit
  38. EP251021b: Einstein Probe detection of a fast X-ray transient
  39. GRB 250911A: MAXI/GSC detection
  40. LIGO/Virgo/KAGRA S251021u: Updated Sky localization
  41. GRB 251016A: SVOM/ECLAIRs refined analysis
  42. LIGO/Virgo/KAGRA S251021u: Identification of a GW compact binary merger candidate
  43. LIGO/Virgo/KAGRA S251018bi: Updated Sky localization
  44. Fermi-LAT gamma-ray observations of IceCube-251018A
  45. GRB 251017A : RAPAS follow-up observations
  46. IceCube-251018A: Upper limits from a search for additional neutrino events in IceCube
  47. GRB 251017A: COLIBRÍ optical observations of a late plateau
  48. IceCube-251018A: DDOTI Optical Upper Limit
  49. GRB 251017A: Swift-BAT refined analysis
  50. GRB 251016A: Fermi GBM Observation
  51. GRB 251018A: Fermi GBM Observation
  52. GRB 251018A: BOOTES-5 and BOOTES-7 early optical detections
  53. GRB 251018A: Swift-XRT refined Analysis
  54. GRB 251018A: Enhanced Swift-XRT position
  55. Fermi trigger No 782500909: Global MASTER-Net observations report
  56. GRB 251016A: HXMT/HE detection
  57. IceCube-251018A: Global MASTER-Net observations report
  58. LIGO/Virgo/KAGRA S251018bi: Identification of a GW compact binary merger candidate
  59. GRB 251016A: Swift-XRT afterglow detection
  60. GRB 251017A: Swift/UVOT Detection
  61. GRB 251016A: Swift/UVOT Detection
  62. GRB 251018A: Swift/UVOT Detection
  63. IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event
  64. IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event (duplicate submission)
  65. GRB 251017A: VLT/MUSE spectroscopic redshift z = 4.327
  66. GRB 251016A: VLT/FORS2 Optical Observation
  67. GRB 251017A: COLIBRÍ photometric redshift
  68. GRB 251017A: Swift-XRT refined Analysis
  69. GRB 251018A: MASTER OT detection
  70. GRB 251018A: TRT optical afterglow detection
  71. Swift GRB 251018A: Global MASTER-Net observations report
  72. GRB 251018A: Swift detection of a burst with an optical counterpart
  73. GRB 251018A: Fermi GBM Final Real-time Localization
  74. GRB 251017A: SVOM/VT optical observation
  75. GRB 251011A: Fermi GBM Observation
  76. GRB 251017A: OHP/T193 i-band observations
  77. GRB 251013C: OHP/T193 third epoch optical observations and detected rebrightening
  78. LIGO/Virgo/KAGRA S251017di: Retraction of GW compact binary merger candidate
  79. GRB 251017A: J-band detection with WINTER
  80. GRB 251017A: Glowbug gamma-ray detection
  81. GRB 251013C: Liverpool Telescope observations
  82. GRB 251013C: Leavitt Observatory optical photometry
  83. Fermi GRB 251016B: Global MASTER-Net observations report
  84. GRB 251017A: JinShan observations of the optical afterglow
  85. Swift GRB 251017A: Global MASTER-Net observations report
  86. GRB 251017A : MITSuME Akeno optical afterglow candidate detection
  87. Swift Trigger 1404295 is not a GRB
  88. GRB 251016A: AstroSat CZTI detection of a short burst
  89. GRB 251017A: Enhanced Swift-XRT position
  90. GRB 251017A: COLIBRÍ Early Afterglow Detection
  91. GRB 251016B: AstroSat CZTI detection
  92. GRB 251017A: BOOTES-5/JGT early optical afterglow detection
  93. GRB 251017A: Swift detection of a burst with an optical counterpart
  94. GRB 251016A: CALET Gamma-Ray Burst Monitor detection
  95. GRB 251016B: CALET Gamma-Ray Burst Monitor detection
  96. GRB 251013C: JinShan observations of the non-thermal rebrightening of the optical counterpart
  97. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) observations of a strong and late rebrightening of the optical counterpart
  98. GRB 251007B: Swift-BAT refined analysis
  99. GRB 251016B: Fermi GBM Final Real-time Localization
  100. GRB 251014D: Swift-BAT refined analysis

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