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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: Swift/BAT-GUANO detection of a long burst outside the coded FOV
  2. LIGO/Virgo/KAGRA S231020bw: Upper limits from Swift/BAT-GUANO
  3. LIGO/Virgo/KAGRA S231021az: Coverage and upper limits from MAXI/GSC observations
  4. LIGO/Virgo/KAGRA S231020bw: Updated Sky localization
  5. GRB 231020A: Fermi GBM Detection
  6. GRID detection of GRB 231004A
  7. GRB 231017A: Mondy optical observations. A possible candidate for an afterglow or host galaxy.
  8. GRB 231019A: VZLUSAT-2 detection
  9. GRB 231018A: VZLUSAT-2 detection
  10. GRB 231020B: BALROG localization (Fermi Trigger 719530557 / GRB 231020900)
  11. LIGO/Virgo/KAGRA S231020ba: Updated Sky localization and EM Bright Classification
  12. GRB 231020B: Fermi GBM Final Real-time Localization
  13. GRB 231020A: BALROG localization (Fermi Trigger / GRB 231020790)
  14. LIGO/Virgo/KAGRA S231020ba: Upper limits from Fermi-GBM Observations
  15. GRB 231015A: NuSTAR Detection of Prompt Emission
  16. Fermi GRB 231020A: Global MASTER-Net observations report
  17. LIGO/Virgo/KAGRA S231020bw: Identification of a GW compact binary merger candidate
  18. GRB 231020A: Fermi GBM Final Real-time Localization
  19. GRB 231012A: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 705709044)
  20. LIGO/Virgo/KAGRA S231020ba: Coverage and upper limits from MAXI/GSC observations
  21. GRB 231017A: 1.3m DFOT Optical upper limit
  22. LIGO/Virgo/KAGRA S231020ba: Identification of a GW compact binary merger candidate
  23. IceCube-231004A: Upper limits from Fermi-GBM Observations
  24. GRB 231018A: GRBAlpha detection
  25. GRB 231018A: CALET Gamma-Ray Burst Monitor detection
  26. Fermi GRB 231019A: Global MASTER-Net observations report
  27. GRB 231018A: Glowbug gamma-ray detection
  28. Konus-Wind detection of GRB 231018A
  29. IPN triangulation of GRB 231018A
  30. GRB 231017A: Swift/UVOT Upper Limit
  31. GRB 230911C: ATCA detection of possible radio counterpart
  32. GRB 231019A: Fermi GBM Final Real-time Localization
  33. GRB 231017A: GOTO optical upper limits
  34. GRB 231017A: JinShan optical upper limit
  35. GRB 231018A: GROWTH-India Follow-Up of a Fermi Long GRB
  36. LIGO/Virgo/KAGRA S231018cb: One counterpart neutrino candidate event from an IceCube neutrino search
  37. IC231004A: Classification of AT2023uqf/ZTF23abidzvf as a rapidly-evolving supernova with CSM interaction
  38. GRB 231017A: Las Cumbres optical upper limit
  39. GRB 231015A: Glowbug gamma-ray detection
  40. GRB 231017A: LCOGT Optical Upper Limits
  41. GRB231017A: GROWTH-India upper limits on the optical afterglow
  42. GRB 231015A: AstroSat CZTI detection
  43. GRB 231018A: Fermi GBM Detection
  44. GRB 231017A: Fermi GBM Detection
  45. GRB 231017A: Swift-XRT observations
  46. GRB 231012B may not be a GRB
  47. GRB 231018A: BALROG localization (Fermi Trigger / GRB 231018521)
  48. GRB 231018A: Fermi GBM Final Real-time Localization
  49. GRB 231017A: Swift ToO observations
  50. GRB 231017A: Swift/BAT-GUANO candidate arcminute localization of a burst
  51. Fermi-LAT gamma-ray observations of IceCube-231014A
  52. GRB231017A: Fermi GBM Final Localization
  53. IceCube-231014A: Upper limits from a search for additional neutrino events in IceCube
  54. LIGO/Virgo/KAGRA S231014r: Upper limits from Swift/BAT-GUANO
  55. (correction) Discovery of an optical transient with strong flaring activity: a new blazar candidate in the Messier 31 field
  56. Discovery of an optical transient with strong flaring activity: a new blazar candidate in the Messier 31 field.
  57. IceCube-231014A - IceCube observation of a high-energy neutrino candidate track-like event
  58. LIGO/Virgo/KAGRA S231014r: Identification of a GW compact binary merger candidate
  59. Correction in GCN 34814: GRB 231012B (not GRB 231012A)
  60. GRB 231012A: Fermi GBM Final Real-time Localization
  61. GRB 231012A: Fermi GBM Final Real-time Localization
  62. GRB 231004A: Glowbug gamma-ray detection
  63. LIGO/Virgo/KAGRA S231001aq: Updated Sky localization
  64. IceCube-231004A: One Candidate Counterpart from the Zwicky Transient Facility
  65. LIGO/Virgo/KAGRA S231005j: Upper limits from Swift/BAT-GUANO
  66. LIGO/Virgo/KAGRA S231008ap: Updated Sky localization
  67. LIGO/Virgo/KAGRA S231008ap: Identification of a GW compact binary merger candidate
  68. IceCube-231004A: Upper limits from a search for additional neutrino events in IceCube
  69. IceCube-231004A: No significant detection in HAWC
  70. GRB 231004A: CALET Gamma-Ray Burst Monitor detection
  71. Fermi-LAT gamma-ray observations of IceCube-231004A
  72. LIGO/Virgo/KAGRA S231005ah: Updated Sky localization
  73. LIGO/Virgo/KAGRA S231005ah: Identification of a GW compact binary merger candidate
  74. LIGO/Virgo/KAGRA S231005j: Updated Sky localization
  75. LIGO/Virgo/KAGRA S231005j: Identification of a GW compact binary merger candidate
  76. Update of IceCube-231004A - Corrected direciton
  77. IceCube-231004A - IceCube observation of a high-energy neutrino candidate track-like event
  78. transient AT2023sva: radio observations with AMI-LA
  79. GRB 231004A: Fermi GBM Final Real-time Localization
  80. GRB 231003A is not a GRB
  81. GRB 231003A: Fermi GBM Final Real-time Localization
  82. LIGO/Virgo/KAGRA S231001aq: Upper limits from Swift/BAT-GUANO
  83. LIGO/Virgo/KAGRA S230930al: Upper limits from Swift/BAT-GUANO
  84. LIGO/Virgo/KAGRA S230928cb: Upper limits from Swift/BAT-GUANO
  85. GRB 230827B: 10.4m GTC spectroscopic redshift
  86. LIGO/Virgo/KAGRA S231001aq: Updated Sky localization
  87. LIGO/Virgo/KAGRA S230930al: Updated Sky localization
  88. LIGO/Virgo/KAGRA S230928cb: Updated Sky localization
  89. LIGO/Virgo/KAGRA S231001aq: Identification of a GW compact binary merger candidate
  90. GRB 230930A: Fermi GBM Final Real-time Localization
  91. LIGO/Virgo/KAGRA S230930al: Identification of a GW compact binary merger candidate
  92. NuEm-230927A: Swift-XRT follow-up
  93. LIGO/Virgo/KAGRA S230928cb: Identification of a GW compact binary merger candidate
  94. AT2023sva / GRB230916B: GIT observations of the afterglow
  95. transient AT2023sva: A Binary Driven Hypernova with a possible associated supernova
  96. LIGO/Virgo/KAGRA S230927be: Updated Sky localization
  97. LIGO/Virgo/KAGRA S230927l: Updated Sky localization
  98. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-230927A
  99. LIGO/Virgo/KAGRA S230927be: Identification of a GW compact binary merger candidate
  100. Swift Triggers 1192745 and 1192747 are not astrophysical events

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