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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 231018A: GRBAlpha detection
  2. GRB 231018A: CALET Gamma-Ray Burst Monitor detection
  3. Fermi GRB 231019A: Global MASTER-Net observations report
  4. GRB 231018A: Glowbug gamma-ray detection
  5. Konus-Wind detection of GRB 231018A
  6. IPN triangulation of GRB 231018A
  7. GRB 231017A: Swift/UVOT Upper Limit
  8. GRB 230911C: ATCA detection of possible radio counterpart
  9. GRB 231019A: Fermi GBM Final Real-time Localization
  10. GRB 231017A: GOTO optical upper limits
  11. GRB 231017A: JinShan optical upper limit
  12. GRB 231018A: GROWTH-India Follow-Up of a Fermi Long GRB
  13. LIGO/Virgo/KAGRA S231018cb: One counterpart neutrino candidate event from an IceCube neutrino search
  14. IC231004A: Classification of AT2023uqf/ZTF23abidzvf as a rapidly-evolving supernova with CSM interaction
  15. GRB 231017A: Las Cumbres optical upper limit
  16. GRB 231015A: Glowbug gamma-ray detection
  17. GRB 231017A: LCOGT Optical Upper Limits
  18. GRB231017A: GROWTH-India upper limits on the optical afterglow
  19. GRB 231015A: AstroSat CZTI detection
  20. GRB 231018A: Fermi GBM Detection
  21. GRB 231017A: Fermi GBM Detection
  22. GRB 231017A: Swift-XRT observations
  23. GRB 231012B may not be a GRB
  24. GRB 231018A: BALROG localization (Fermi Trigger / GRB 231018521)
  25. GRB 231018A: Fermi GBM Final Real-time Localization
  26. GRB 231017A: Swift ToO observations
  27. GRB 231017A: Swift/BAT-GUANO candidate arcminute localization of a burst
  28. Fermi-LAT gamma-ray observations of IceCube-231014A
  29. GRB231017A: Fermi GBM Final Localization
  30. IceCube-231014A: Upper limits from a search for additional neutrino events in IceCube
  31. LIGO/Virgo/KAGRA S231014r: Upper limits from Swift/BAT-GUANO
  32. (correction) Discovery of an optical transient with strong flaring activity: a new blazar candidate in the Messier 31 field
  33. Discovery of an optical transient with strong flaring activity: a new blazar candidate in the Messier 31 field.
  34. IceCube-231014A - IceCube observation of a high-energy neutrino candidate track-like event
  35. LIGO/Virgo/KAGRA S231014r: Identification of a GW compact binary merger candidate
  36. Correction in GCN 34814: GRB 231012B (not GRB 231012A)
  37. GRB 231012A: Fermi GBM Final Real-time Localization
  38. GRB 231012A: Fermi GBM Final Real-time Localization
  39. GRB 231004A: Glowbug gamma-ray detection
  40. LIGO/Virgo/KAGRA S231001aq: Updated Sky localization
  41. IceCube-231004A: One Candidate Counterpart from the Zwicky Transient Facility
  42. LIGO/Virgo/KAGRA S231005j: Upper limits from Swift/BAT-GUANO
  43. LIGO/Virgo/KAGRA S231008ap: Updated Sky localization
  44. LIGO/Virgo/KAGRA S231008ap: Identification of a GW compact binary merger candidate
  45. IceCube-231004A: Upper limits from a search for additional neutrino events in IceCube
  46. IceCube-231004A: No significant detection in HAWC
  47. GRB 231004A: CALET Gamma-Ray Burst Monitor detection
  48. Fermi-LAT gamma-ray observations of IceCube-231004A
  49. LIGO/Virgo/KAGRA S231005ah: Updated Sky localization
  50. LIGO/Virgo/KAGRA S231005ah: Identification of a GW compact binary merger candidate
  51. LIGO/Virgo/KAGRA S231005j: Updated Sky localization
  52. LIGO/Virgo/KAGRA S231005j: Identification of a GW compact binary merger candidate
  53. Update of IceCube-231004A - Corrected direciton
  54. IceCube-231004A - IceCube observation of a high-energy neutrino candidate track-like event
  55. transient AT2023sva: radio observations with AMI-LA
  56. GRB 231004A: Fermi GBM Final Real-time Localization
  57. GRB 231003A is not a GRB
  58. GRB 231003A: Fermi GBM Final Real-time Localization
  59. LIGO/Virgo/KAGRA S231001aq: Upper limits from Swift/BAT-GUANO
  60. LIGO/Virgo/KAGRA S230930al: Upper limits from Swift/BAT-GUANO
  61. LIGO/Virgo/KAGRA S230928cb: Upper limits from Swift/BAT-GUANO
  62. GRB 230827B: 10.4m GTC spectroscopic redshift
  63. LIGO/Virgo/KAGRA S231001aq: Updated Sky localization
  64. LIGO/Virgo/KAGRA S230930al: Updated Sky localization
  65. LIGO/Virgo/KAGRA S230928cb: Updated Sky localization
  66. LIGO/Virgo/KAGRA S231001aq: Identification of a GW compact binary merger candidate
  67. GRB 230930A: Fermi GBM Final Real-time Localization
  68. LIGO/Virgo/KAGRA S230930al: Identification of a GW compact binary merger candidate
  69. NuEm-230927A: Swift-XRT follow-up
  70. LIGO/Virgo/KAGRA S230928cb: Identification of a GW compact binary merger candidate
  71. AT2023sva / GRB230916B: GIT observations of the afterglow
  72. transient AT2023sva: A Binary Driven Hypernova with a possible associated supernova
  73. LIGO/Virgo/KAGRA S230927be: Updated Sky localization
  74. LIGO/Virgo/KAGRA S230927l: Updated Sky localization
  75. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-230927A
  76. LIGO/Virgo/KAGRA S230927be: Identification of a GW compact binary merger candidate
  77. Swift Triggers 1192745 and 1192747 are not astrophysical events
  78. LIGO/Virgo/KAGRA S230927l: Identification of a GW compact binary merger candidate
  79. Swift Triggers 1192740, 1192742 and 1192743 are not astrophysical events
  80. Swift Triggers 1192735 and 1192737 are not astrophysical events
  81. LIGO/Virgo/KAGRA S230922q: Updated Sky localization
  82. Konus-Wind detection of GRB 230919A
  83. LIGO/Virgo/KAGRA S230924an: Upper limits from Swift/BAT-GUANO
  84. LIGO/Virgo/KAGRA S230920al: Upper limits from Swift/BAT-GUANO
  85. LIGO/Virgo/KAGRA S230919bj: Upper limits from Swift/BAT-GUANO
  86. Fermi Gamma-ray Burst Monitor trigger 717299390/230925076 is not a GRB
  87. Fermi Gamma-ray Burst Monitor trigger 230925241/717313591 is not a GRB
  88. LIGO/Virgo/KAGRA S230922g: DECam GW-MMADS candidates
  89. GRB 230812B: r'-band observations from MISTRAL at Observatoire de Haute-Provence
  90. LIGO/Virgo/KAGRA S230924an: Updated Sky localization
  91. LIGO/Virgo/KAGRA S230924an: Identification of a GW compact binary merger candidate
  92. LIGO/Virgo/KAGRA S230917af: GRAWITA wide-field observations
  93. LIGO/Virgo/KAGRA S230922g: Updated Sky localization
  94. LIGO/Virgo/KAGRA S230922g: Identification of a GW compact binary merger candidate
  95. LIGO/Virgo/KAGRA S230922q: Identification of a GW compact binary merger candidate
  96. LIGO/Virgo/KAGRA S230917af: Zwicky Transient Facility observations
  97. GRB 230921A: Fermi GBM Final Real-time Localization
  98. GRB 230918B: VLT/X-shooter classification of AT 2023tbf (GOTO23aky) as a dwarf nova
  99. IPN triangulation of GRB 230919A (short)
  100. LIGO/Virgo/KAGRA S230904n: Classification of the candidate AT2023rkw with DBSP

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