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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. LIGO/Virgo/KAGRA S231113bw: Upper limits from Fermi-GBM Observations
  2. GRB 231110A: CALET Gamma-Ray Burst Monitor detection
  3. LIGO/Virgo/KAGRA S231113cd: Coverage and upper limits from MAXI/GSC observations
  4. LIGO/Virgo/KAGRA S231113bb: Updated Sky localization
  5. LIGO/Virgo/KAGRA S231113bw: Coverage and upper limits from MAXI/GSC observations
  6. LIGO/Virgo/KAGRA S231113bw: Identification of a GW compact binary merger candidate
  7. GRB 231110A: Swift-BAT refined analysis
  8. GRB231111A: MDM 2.4m Hiltner Telescope Observation
  9. GRB 231106A: Glowbug gamma-ray detection
  10. GRB 231111A: Xinglong-2.16m optical observations
  11. GRB 231110A: Swift-UVOT Upper Limits
  12. LIGO/Virgo/KAGRA S231113bb: Identification of a GW compact binary merger candidate
  13. GRB 231111A: Afterglow redshift from OSIRIS+/GTC
  14. GRB 231104A: VZLUSAT-2 detection
  15. GRB 231111A: TNG tentative redshift
  16. GRB 231110A: Glowbug gamma-ray detection
  17. GRB 231110A: AstroSat CZTI detection
  18. GRB 231111A NUTTelA-TAO / BSTI Early Measurements
  19. GRB 231111A: Leavitt Observatory optical observations
  20. GRB231111A: Optical follow-up observations with Mephisto
  21. GRB 231111A: GMG observation (correction)
  22. LIGO/Virgo/KAGRA S231112ag: Retraction of GW compact binary merger candidate
  23. GRB 231111A: GMG observation upper limit
  24. GRB 231106B: GRBAlpha detection
  25. GRB 231111A: Osservatorio Astronomico "Nastro Verde" optical observations with detection of an optical counterpart
  26. GRB 231110A: Terskol Zeiss-2000 optical upper limit
  27. GRB 231111A: Swift-XRT refined Analysis
  28. GRB 231111A: Mondy optical observations
  29. GRB 231111A: GECAM-C detection of a long burst (correction)
  30. GRB 231110A: GECAM-B detection (correction)
  31. GRB 231111A: Enhanced Swift-XRT position
  32. GRB 231111A: GECAM-C detection of a long burst
  33. GRB 231110A: GECAM detection
  34. GRB 231110A: GOTO optical upper limits
  35. GRB 231110A: SAO RAS optical observations
  36. GRB 231110A: Swift-XRT afterglow detection
  37. GRB231111A: YAHPT Observations
  38. GRB231111A: GIT confirmation of the optical afterglow
  39. GRB 231111A: MASTER OT earlier detection
  40. GRB 231111A: Nanshan/HMT optical observations
  41. GRB 231111A: Swift detection of a burst with an optical counterpart
  42. Swift GRB231111.60: Global MASTER-Net observations report
  43. GRB231110A: WFST Observation and upper limits
  44. Swift GRB231110.89: Global MASTER-Net observations report
  45. GRB 231110A: Swift detection of a burst
  46. LIGO/Virgo/KAGRA S231110g: Updated Sky localization
  47. LIGO/Virgo/KAGRA S231110g: Identification of a GW compact binary merger candidate
  48. GRB 231109A: Fermi GBM Final Localization
  49. IceCube-231103A: No candidates from the Zwicky Transient Facility
  50. LIGO/Virgo/KAGRA S231108u: Updated Sky localization
  51. Fermi trigger No 721204446: Global MASTER-Net observations report
  52. Fermi GRB 231108A: Global MASTER-Net observations report
  53. GRB 231108A: Fermi GBM Final Real-time Localization
  54. LIGO/Virgo/KAGRA O4 Landscape
  55. LIGO/Virgo/KAGRA S231108u: Identification of a GW compact binary merger candidate
  56. GRB 231106A: AstroSat CZTI detection
  57. GRB 231106A: CALET Gamma-Ray Burst Monitor detection
  58. GRB 231104A: Swift-BAT refined analysis
  59. Fermi trigger No 721006392: Global MASTER-Net observations report
  60. Fermi Gamma-ray Burst Monitor trigger 231107654 / 721064512 is not a GRB
  61. GRB 231104A: FRAM-ORM optical limit
  62. LIGO/Virgo/KAGRA S231102w: Upper limits from Swift/BAT-GUANO
  63. Fermi GRB 231106A: Global MASTER-Net observations report
  64. GRB 231104A: Wendelstein Optical/Infrared Observations
  65. GRB 231104A: NuSTAR Observation of the prompt emission
  66. GRB 231106A: Fermi GBM Final Real-time Localization
  67. GRB 231104A: 3.6m DOT optical upper limit
  68. IceCube-231103A: Upper limits from a search for additional neutrino events in IceCube
  69. LIGO/Virgo/KAGRA S231106y: one counterpart neutrino candidate from IceCube neutrino searches
  70. Fermi-LAT gamma-ray observations of IceCube-231103A
  71. GRB 231104A: NOT upper limit
  72. GRB 231104A: Fermi GBM Observation
  73. GRB 231104B: Fermi GBM Final Real-time Localization
  74. Fermi GRB 231103A: Global MASTER-Net observations report
  75. LIGO/Virgo/KAGRA S231104ac: Updated Sky localization
  76. GRB 231104A: AKO Upper Limit
  77. GRB 231104A: AstroSat CZTI detection
  78. GRB 231104A: Swift-XRT refined Analysis
  79. GRB 231104A: Fermi-LAT detection
  80. LIGO/Virgo/KAGRA S231104ac: Identification of a GW compact binary merger candidate
  81. GRB 231104A: Swift/UVOT Upper Limits
  82. GRB 231104A: Enhanced Swift-XRT position
  83. GRB231104A: LCOGT Optical Upper Limits
  84. GRB 231104A: Swift detection of a bright burst
  85. GRB 231104A: Fermi GBM Final Real-time Localization
  86. Swift GRB231104.07: Global MASTER-Net observations report
  87. IceCube Alert 231103.39: Global MASTER-Net observations report
  88. GRB 231103A: Fermi GBM Final Real-time Localization
  89. IceCube-231103A - IceCube observation of a high-energy neutrino candidate track-like event
  90. Fermi-LAT gamma-ray observations of IceCube-231027A
  91. LIGO/Virgo/KAGRA S231102w: Updated Sky localization
  92. LIGO/Virgo/KAGRA S231102i: Global MASTER-Net observations report
  93. GRB 231101A: Glowbug gamma-ray detection
  94. GRB 231024A: GRANDMA observations of AT2023vuc/GOTO23baj candidate
  95. LIGO/Virgo/KAGRA S231102w: Identification of a GW compact binary merger candidate
  96. New Swift-BAT/GUANO and IceCube Notices Available via GCN Kafka
  97. Fermi trigger No 720498201: Global MASTER-Net observations report
  98. GRB 231101A: Fermi GBM Final Real-time Localization
  99. GRB 231030B: GRBAlpha detection
  100. GRB 231028B: VZLUSAT-2 detection

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