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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 231210B: Swift detection of a burst with optical counterpart
  2. Swift GRB231210.90: Global MASTER-Net OT detection
  3. Swift GRB231210.90: Global MASTER-Net observations report
  4. IPN triangulation of GRB 231129C
  5. GRB 231210A: Fermi GBM Final Real-time Localization
  6. GRB 231208A: GRBAlpha detection
  7. GRB231205B: Swift/UVOT Upper Limits
  8. GRB 231208A: Glowbug gamma-ray detection
  9. GRB 231208A: AstroSat CZTI detection of a faint burst
  10. LIGO/Virgo/KAGRA S231206ca: Updated Sky localization
  11. IPN triangulation of GRB 231205A
  12. GRB 231205B: Swift-BAT refined analysis
  13. GRB 231205B: 1.3m DFOT Optical upper limit
  14. LIGO/Virgo/KAGRA S231206cc: Updated Sky localization and Source Classification
  15. GRB 231206A: joint location of multiple instruments by ETJASMIN
  16. GRB 231205B: optical upper limit in TSHAOand AbAO
  17. LIGO/Virgo/KAGRA S231206cc: Identification of a GW compact binary merger candidate
  18. LIGO/Virgo/KAGRA S231206ca: Identification of a GW compact binary merger candidate
  19. GRB231115A: TURBO Pre-Burst Optical Upper Limits
  20. GRB 231205B: AGILE detection
  21. Fermi trigger No 723581802: Global MASTER-Net observations report
  22. GRB 231206B: Fermi GBM Final Real-time Localization
  23. GRB 231205B: Ondrejov D50 optical upper limit
  24. GRB 231205B: Swift-XRT refined Analysis
  25. Fermi-LAT gamma-ray observations of IceCube-231202A
  26. GRB 231205B: REM optical/NIR upper limits
  27. GRB 231129C: ASIM MXGS observation and localization
  28. GRB 231205B: NUTTelA-TAO / BSTI Early Optical Limits
  29. GRB 231205B: r'-band observations from MISTRAL at Observatoire de Haute-Provence
  30. GRB 231206A: GECAM-B detection of a short burst (correction)
  31. GRB 231205B : MITSuME Akeno optical upper limits
  32. GRB 231206A: GECAM-B detection of a short burst
  33. GRB 231205B: Zadko observatory - Gingin optical observations
  34. GRB 231205B: Gaoyazi/GOT optical upper limit
  35. GRB 231205B: Nanshan/HMT optical upper limit
  36. GRB 231205B: GECAM-B detection of a long burst
  37. GRB 231205B: LCOGT Optical Upper Limits
  38. GRB 231205A: DDOTI Upper Limits on the Afterglow
  39. LIGO/Virgo/KAGRA S231205c: One counterpart neutrino candidate event from an IceCube neutrino search
  40. GRB 231205B: Enhanced Swift-XRT position
  41. GRB 231204A: Glowbug gamma-ray detection
  42. Swift GRB231205.70: Global MASTER-Net observations report
  43. GRB 231204A: CALET Gamma-Ray Burst Monitor detection
  44. Fermi-LAT daily aperture light curve of T CrB now available
  45. GRB 231205B: AKO Optical Upper Limit
  46. GRB 231205B: Swift detection of a burst
  47. GRB 231205A: joint location of multiple instruments by ETJASMIN
  48. GRB 231204A: AstroSat CZTI detection
  49. GRB 231205A: GECAM-B detection of a short burst
  50. Fermi trigger No 723435916: Global MASTER-Net observations report
  51. Fermi trigger No 723326169: Global MASTER-Net observations report
  52. GRB 231205A: Fermi GBM Final Real-time Localization
  53. LIGO/Virgo/KAGRA S231129ac: Upper limits from Swift/BAT-GUANO
  54. IceCube-231202A: Upper limits from a search for additional neutrino events in IceCube
  55. Fermi trigger No 723412808: Global MASTER-Net observations report
  56. GRB 231203A: Fermi GBM Observation
  57. GRB 231204A: Fermi GBM Final Real-time Localization
  58. GRB 231203A: Swift/BAT-GUANO detection of a burst outside the coded FOV
  59. Konus-Wind detection of GRB 231129C
  60. IceCube-231202A - IceCube observation of a high-energy neutrino candidate track-like event
  61. Fermi trigger No 723279695: Global MASTER-Net observations report
  62. The Fermi GBM team reports the detection of a likely SHORT GRB
  63. GRB 231203A: Fermi GBM Final Real-time Localization
  64. GRB 231129C: Swift-XRT afterglow detection
  65. Fermi trigger No 723149952: Global MASTER-Net observations report
  66. GRB 231129C: PROMPT optical upper limits for the MAXI/GSC X-ray counterpart and the MASTER afterglow candidate
  67. GRB 231129A: VZLUSAT-2 detection
  68. GRB 231129B: Swift-XRT observations
  69. GRB 231128A: VZLUSAT-2 detection
  70. Optical transient in the field of Messier 31, likely a new blazar: back to bright state
  71. GRB 231129C: AGILE detection
  72. GRB 231129A : MITSuME Akeno optical upper limits
  73. GRB 231129C: Swift/BAT-GUANO localization of a burst outside the coded FOV
  74. GRB 231129A: Swift-BAT refined analysis
  75. GRB 231129C: MASTER OT detection
  76. GRB 231129A: BOOTES-5/JGT optical upper limit
  77. GRB 231129C: Fermi-LAT detection
  78. GRB 231129A: JinShan optical upper limit
  79. GRB 231129C: GRBAlpha detection
  80. GRB 231129C: Glowbug gamma-ray detection
  81. GRB 231129C: Swift-XRT observations
  82. GRB 231129A: Swift/UVOT Upper Limits
  83. GRB 231129A: optical upper limit in Mondy observatory
  84. GRB 231129C: GECAM-B detection of a bright burst
  85. GRB 231129C: AstroSat CZTI detection
  86. GRB 231129C: iTelescope OT retraction
  87. GRB 231129C: CALET Gamma-Ray Burst Monitor detection
  88. GRB 231129C: Fermi GBM Observation of a very bright GRB
  89. GRB 231129C: iTelescope likely optical afterglow AT 2023yph discovery
  90. GRB 231129C: Tiled Swift observations
  91. GRB 231127A: GRBAlpha detection
  92. GRB 231129C: MAXI/GSC detection
  93. GRB 231129C: BALROG localization (Fermi Trigger / GRB 231129799)
  94. GRB 231129C: Fermi GBM detection of a very bright burst
  95. GRB 231129A: Enhanced Swift-XRT position
  96. LIGO/Virgo/KAGRA S231129ac: Updated Sky localization
  97. GRB 231129A: Swift-XRT refined Analysis
  98. GRB 231129C: Fermi GBM Final Real-time Localization
  99. Fermi trigger No 722977823: Global MASTER-Net observations report
  100. GRB 231129B: Tiled Swift observations

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