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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').
  1. GRB 231017A: Swift-XRT observations
  2. GRB 231012B may not be a GRB
  3. GRB 231018A: BALROG localization (Fermi Trigger / GRB 231018521)
  4. GRB 231018A: Fermi GBM Final Real-time Localization
  5. GRB 231017A: Swift ToO observations
  6. GRB 231017A: Swift/BAT-GUANO candidate arcminute localization of a burst
  7. Fermi-LAT gamma-ray observations of IceCube-231014A
  8. GRB231017A: Fermi GBM Final Localization
  9. IceCube-231014A: Upper limits from a search for additional neutrino events in IceCube
  10. LIGO/Virgo/KAGRA S231014r: Upper limits from Swift/BAT-GUANO
  11. (correction) Discovery of an optical transient with strong flaring activity: a new blazar candidate in the Messier 31 field
  12. Discovery of an optical transient with strong flaring activity: a new blazar candidate in the Messier 31 field.
  13. IceCube-231014A - IceCube observation of a high-energy neutrino candidate track-like event
  14. LIGO/Virgo/KAGRA S231014r: Identification of a GW compact binary merger candidate
  15. Correction in GCN 34814: GRB 231012B (not GRB 231012A)
  16. GRB 231012A: Fermi GBM Final Real-time Localization
  17. GRB 231012A: Fermi GBM Final Real-time Localization
  18. GRB 231004A: Glowbug gamma-ray detection
  19. LIGO/Virgo/KAGRA S231001aq: Updated Sky localization
  20. IceCube-231004A: One Candidate Counterpart from the Zwicky Transient Facility
  21. LIGO/Virgo/KAGRA S231005j: Upper limits from Swift/BAT-GUANO
  22. LIGO/Virgo/KAGRA S231008ap: Updated Sky localization
  23. LIGO/Virgo/KAGRA S231008ap: Identification of a GW compact binary merger candidate
  24. IceCube-231004A: Upper limits from a search for additional neutrino events in IceCube
  25. IceCube-231004A: No significant detection in HAWC
  26. GRB 231004A: CALET Gamma-Ray Burst Monitor detection
  27. Fermi-LAT gamma-ray observations of IceCube-231004A
  28. LIGO/Virgo/KAGRA S231005ah: Updated Sky localization
  29. LIGO/Virgo/KAGRA S231005ah: Identification of a GW compact binary merger candidate
  30. LIGO/Virgo/KAGRA S231005j: Updated Sky localization
  31. LIGO/Virgo/KAGRA S231005j: Identification of a GW compact binary merger candidate
  32. Update of IceCube-231004A - Corrected direciton
  33. IceCube-231004A - IceCube observation of a high-energy neutrino candidate track-like event
  34. transient AT2023sva: radio observations with AMI-LA
  35. GRB 231004A: Fermi GBM Final Real-time Localization
  36. GRB 231003A is not a GRB
  37. GRB 231003A: Fermi GBM Final Real-time Localization
  38. LIGO/Virgo/KAGRA S231001aq: Upper limits from Swift/BAT-GUANO
  39. LIGO/Virgo/KAGRA S230930al: Upper limits from Swift/BAT-GUANO
  40. LIGO/Virgo/KAGRA S230928cb: Upper limits from Swift/BAT-GUANO
  41. GRB 230827B: 10.4m GTC spectroscopic redshift
  42. LIGO/Virgo/KAGRA S231001aq: Updated Sky localization
  43. LIGO/Virgo/KAGRA S230930al: Updated Sky localization
  44. LIGO/Virgo/KAGRA S230928cb: Updated Sky localization
  45. LIGO/Virgo/KAGRA S231001aq: Identification of a GW compact binary merger candidate
  46. GRB 230930A: Fermi GBM Final Real-time Localization
  47. LIGO/Virgo/KAGRA S230930al: Identification of a GW compact binary merger candidate
  48. NuEm-230927A: Swift-XRT follow-up
  49. LIGO/Virgo/KAGRA S230928cb: Identification of a GW compact binary merger candidate
  50. AT2023sva / GRB230916B: GIT observations of the afterglow
  51. transient AT2023sva: A Binary Driven Hypernova with a possible associated supernova
  52. LIGO/Virgo/KAGRA S230927be: Updated Sky localization
  53. LIGO/Virgo/KAGRA S230927l: Updated Sky localization
  54. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-230927A
  55. LIGO/Virgo/KAGRA S230927be: Identification of a GW compact binary merger candidate
  56. Swift Triggers 1192745 and 1192747 are not astrophysical events
  57. LIGO/Virgo/KAGRA S230927l: Identification of a GW compact binary merger candidate
  58. Swift Triggers 1192740, 1192742 and 1192743 are not astrophysical events
  59. Swift Triggers 1192735 and 1192737 are not astrophysical events
  60. LIGO/Virgo/KAGRA S230922q: Updated Sky localization
  61. Konus-Wind detection of GRB 230919A
  62. LIGO/Virgo/KAGRA S230924an: Upper limits from Swift/BAT-GUANO
  63. LIGO/Virgo/KAGRA S230920al: Upper limits from Swift/BAT-GUANO
  64. Title: LIGO/Virgo/KAGRA S230919bj: Upper limits from Swift/BAT-GUANO
  65. Fermi Gamma-ray Burst Monitor trigger 717299390/230925076 is not a GRB
  66. Fermi Gamma-ray Burst Monitor trigger 230925241/717313591 is not a GRB
  67. LIGO/Virgo/KAGRA S230922g: DECam GW-MMADS candidates
  68. GRB 230812B: r'-band observations from MISTRAL at Observatoire de Haute-Provence
  69. LIGO/Virgo/KAGRA S230924an: Updated Sky localization
  70. LIGO/Virgo/KAGRA S230924an: Identification of a GW compact binary merger candidate
  71. LIGO/Virgo/KAGRA S230917af: GRAWITA wide-field observations
  72. LIGO/Virgo/KAGRA S230922g: Updated Sky localization
  73. LIGO/Virgo/KAGRA S230922g: Identification of a GW compact binary merger candidate
  74. LIGO/Virgo/KAGRA S230922q: Identification of a GW compact binary merger candidate
  75. LIGO/Virgo/KAGRA S230917af: Zwicky Transient Facility observations
  76. GRB 230921A: Fermi GBM Final Real-time Localization
  77. GRB 230918B: VLT/X-shooter classification of AT 2023tbf (GOTO23aky) as a dwarf nova
  78. IPN triangulation of GRB 230919A (short)
  79. LIGO/Virgo/KAGRA S230904n: Classification of the candidate AT2023rkw with DBSP
  80. GRB 230919A: Fermi GBM Observation
  81. Correction to Fermi GBM Statement for Trigger 716527670/230916144
  82. Fermi GBM Statement for Trigger 716527670/230916144
  83. GRB 230919A: Swift/BAT-GUANO detection of a possibly short burst outside the coded FOV
  84. LIGO/Virgo/KAGRA S230920al: Updated Sky localization
  85. LIGO/Virgo/KAGRA S230919bj: Updated Sky localization
  86. transient AT2023sva: imaging and spectroscopic observations from MISTRAL at Observatoire de Haute-Provence
  87. GRB 230812B : optical observations from MISTRAL at Observatoire de Haute-Provence
  88. GRB 230919A: AstroSat CZTI detection
  89. LIGO/Virgo/KAGRA S230920al: Identification of a GW compact binary merger candidate
  90. AT2023sva: redshift from OSIRIS+/GTC of the ZTF afterglow
  91. LIGO/Virgo/KAGRA S230919bj: Identification of a GW compact binary merger candidate
  92. GRB 230918B: GOTO detection of a fast-rising transient in the GBM localisation region
  93. GRB 230919A: Fermi GBM Final Real-time Localization
  94. LIGO/Virgo S230917af: Swift XRT observations, 6 X-ray sources
  95. Detection of self-absorbed radio emission from GRB 230812B with the JVLA + uGMRT
  96. GRB 230918B: Fermi GBM Final Real-time Localization
  97. GRB 230918A (short): Glowbug gamma-ray detection
  98. GRB 230916B: Glowbug gamma-ray detection
  99. AT 2023sva: NOT observations of the ZTF candidate afterglow
  100. ZTF and SEDM Observations of the Candidate Optical Afterglow AT 2023sva

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