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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 231003A is not a GRB
  2. GRB 231003A: Fermi GBM Final Real-time Localization
  3. LIGO/Virgo/KAGRA S231001aq: Upper limits from Swift/BAT-GUANO
  4. LIGO/Virgo/KAGRA S230930al: Upper limits from Swift/BAT-GUANO
  5. LIGO/Virgo/KAGRA S230928cb: Upper limits from Swift/BAT-GUANO
  6. GRB 230827B: 10.4m GTC spectroscopic redshift
  7. LIGO/Virgo/KAGRA S231001aq: Updated Sky localization
  8. LIGO/Virgo/KAGRA S230930al: Updated Sky localization
  9. LIGO/Virgo/KAGRA S230928cb: Updated Sky localization
  10. LIGO/Virgo/KAGRA S231001aq: Identification of a GW compact binary merger candidate
  11. GRB 230930A: Fermi GBM Final Real-time Localization
  12. LIGO/Virgo/KAGRA S230930al: Identification of a GW compact binary merger candidate
  13. NuEm-230927A: Swift-XRT follow-up
  14. LIGO/Virgo/KAGRA S230928cb: Identification of a GW compact binary merger candidate
  15. AT2023sva / GRB230916B: GIT observations of the afterglow
  16. transient AT2023sva: A Binary Driven Hypernova with a possible associated supernova
  17. LIGO/Virgo/KAGRA S230927be: Updated Sky localization
  18. LIGO/Virgo/KAGRA S230927l: Updated Sky localization
  19. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-230927A
  20. LIGO/Virgo/KAGRA S230927be: Identification of a GW compact binary merger candidate
  21. Swift Triggers 1192745 and 1192747 are not astrophysical events
  22. LIGO/Virgo/KAGRA S230927l: Identification of a GW compact binary merger candidate
  23. Swift Triggers 1192740, 1192742 and 1192743 are not astrophysical events
  24. Swift Triggers 1192735 and 1192737 are not astrophysical events
  25. LIGO/Virgo/KAGRA S230922q: Updated Sky localization
  26. Konus-Wind detection of GRB 230919A
  27. LIGO/Virgo/KAGRA S230924an: Upper limits from Swift/BAT-GUANO
  28. LIGO/Virgo/KAGRA S230920al: Upper limits from Swift/BAT-GUANO
  29. LIGO/Virgo/KAGRA S230919bj: Upper limits from Swift/BAT-GUANO
  30. Fermi Gamma-ray Burst Monitor trigger 717299390/230925076 is not a GRB
  31. Fermi Gamma-ray Burst Monitor trigger 230925241/717313591 is not a GRB
  32. LIGO/Virgo/KAGRA S230922g: DECam GW-MMADS candidates
  33. GRB 230812B: r'-band observations from MISTRAL at Observatoire de Haute-Provence
  34. LIGO/Virgo/KAGRA S230924an: Updated Sky localization
  35. LIGO/Virgo/KAGRA S230924an: Identification of a GW compact binary merger candidate
  36. LIGO/Virgo/KAGRA S230917af: GRAWITA wide-field observations
  37. LIGO/Virgo/KAGRA S230922g: Updated Sky localization
  38. LIGO/Virgo/KAGRA S230922g: Identification of a GW compact binary merger candidate
  39. LIGO/Virgo/KAGRA S230922q: Identification of a GW compact binary merger candidate
  40. LIGO/Virgo/KAGRA S230917af: Zwicky Transient Facility observations
  41. GRB 230921A: Fermi GBM Final Real-time Localization
  42. GRB 230918B: VLT/X-shooter classification of AT 2023tbf (GOTO23aky) as a dwarf nova
  43. IPN triangulation of GRB 230919A (short)
  44. LIGO/Virgo/KAGRA S230904n: Classification of the candidate AT2023rkw with DBSP
  45. GRB 230919A: Fermi GBM Observation
  46. Correction to Fermi GBM Statement for Trigger 716527670/230916144
  47. Fermi GBM Statement for Trigger 716527670/230916144
  48. GRB 230919A: Swift/BAT-GUANO detection of a possibly short burst outside the coded FOV
  49. LIGO/Virgo/KAGRA S230920al: Updated Sky localization
  50. LIGO/Virgo/KAGRA S230919bj: Updated Sky localization
  51. transient AT2023sva: imaging and spectroscopic observations from MISTRAL at Observatoire de Haute-Provence
  52. GRB 230812B : optical observations from MISTRAL at Observatoire de Haute-Provence
  53. GRB 230919A: AstroSat CZTI detection
  54. LIGO/Virgo/KAGRA S230920al: Identification of a GW compact binary merger candidate
  55. AT2023sva: redshift from OSIRIS+/GTC of the ZTF afterglow
  56. LIGO/Virgo/KAGRA S230919bj: Identification of a GW compact binary merger candidate
  57. GRB 230918B: GOTO detection of a fast-rising transient in the GBM localisation region
  58. GRB 230919A: Fermi GBM Final Real-time Localization
  59. LIGO/Virgo S230917af: Swift XRT observations, 6 X-ray sources
  60. Detection of self-absorbed radio emission from GRB 230812B with the JVLA + uGMRT
  61. GRB 230918B: Fermi GBM Final Real-time Localization
  62. GRB 230918A (short): Glowbug gamma-ray detection
  63. GRB 230916B: Glowbug gamma-ray detection
  64. AT 2023sva: NOT observations of the ZTF candidate afterglow
  65. ZTF and SEDM Observations of the Candidate Optical Afterglow AT 2023sva
  66. GRB 230915A: Fermi GBM observation
  67. LIGO/Virgo/KAGRA S230918aq: Retraction of GW compact binary merger candidate
  68. GRB 230812B: Radio observations with the uGMRT
  69. GRB 230918A: Fermi GBM Final Real-time Localization
  70. GRB 230917A: AstroSat CZTI detection
  71. Swift Triggers 1192480, 1192481, 1192482 and 1192483 are not astrophysical events
  72. LIGO/Virgo/KAGRA S230917af: MAXI/GSC observations
  73. GRB 230915B: Glowbug gamma-ray detection
  74. GRB 230916A: NuSTAR Discovery of Prompt Emission from a Potential GRB
  75. GRB 230911A: Fermi GBM Observation
  76. Swift GRB230916.18: Global MASTER-Net observations report
  77. Fermi trigger No 716572242: Global MASTER-Net observations report
  78. LIGO/Virgo/KAGRA S230904n: Correction of the coordinates of the ZTF candidate counterpart
  79. Fermi trigger No 716544961: Global MASTER-Net observations report
  80. Fermi-LAT gamma-ray observations of IceCube-230914A
  81. GRB 230915A: Swift/BAT-GUANO detection of a burst
  82. LIGO/Virgo/KAGRA S230914ak: Upper limits from Swift/BAT-GUANO
  83. GRB 230911D: GRBAlpha detection
  84. Swift GRB230916.19: Global MASTER-Net observations report
  85. Swift GRB230916.18: Global MASTER-Net observations report
  86. Swift Triggers 1192234, 1192235 and 1192236 are not astrophysical events
  87. Swift GRB230916.13: Global MASTER-Net observations report
  88. Swift GRB230916.12: Global MASTER-Net observations report
  89. Swift GRB230916.11: Global MASTER-Net observations report
  90. Swift Trigger 1192233 is not a GRB
  91. GRB 230906A: optical counterpart
  92. IceCube-230914A: Upper limits from a search for additional neutrino events in IceCube
  93. GRB 230911A: Swift-XRT afterglow detection
  94. Fermi trigger No 716449174: Global MASTER-Net observations report
  95. GRB 230913A: CALET Gamma-Ray Burst Monitor detection
  96. IceCube Alert 230914.22: Global MASTER-Net observations report
  97. Swift Trigger 1192088 is not an astrophysical event
  98. Fermi trigger No 716419312: Global MASTER-Net observations report
  99. GRB 230913A: Glowbug gamma-ray detection
  100. LIGO/Virgo/KAGRA S230914ak: Updated Sky localization

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