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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. IceCube-230724A: JCMT/SCUBA-2 submm observations
  2. IceCube-230707A: JCMT/SCUBA-2 submm observations
  3. LIGO/Virgo/KAGRA S230731an: Upper limits from Swift/BAT-GUANO
  4. GRB 230723A: SPT-3G millimeter-band transient event inconsistent with IPN position
  5. LIGO/Virgo/KAGRA S230731an: AstroSat CZTI non-detection and upper limits
  6. LIGO/Virgo/KAGRA S230731an: not observable by Fermi-GBM
  7. LIGO/Virgo/KAGRA S230731an: Updated Sky Localization and EM Bright Classification, and Correction to Source Classification
  8. GRB 230731A: Fermi GBM Final Real-time Localization
  9. LIGO/Virgo/KAGRA S230731an: Coverage and upper limits from MAXI/GSC observations
  10. LIGO/Virgo/KAGRA S230731an: Identification of a GW compact binary merger candidate
  11. LIGO/Virgo/KAGRA S230729z: Updated Sky localization
  12. GRB 230723A: Detection of candidate millimeter-band radiation by SPT-3G
  13. Fermi trigger No 712390645: Global MASTER-Net observations report
  14. GRB 230728A: Swift-BAT refined analysis
  15. Fermi-LAT gamma-ray observations of IceCube-230727A
  16. GRB 230723B: Swift-BAT refined analysis
  17. Fermi trigger No 712306969: Global MASTER-Net observations report
  18. GRB 230723B: MITSuME Ishigaki optical observation
  19. IceCube-230727A: No candidates from the Zwicky Transient Facility
  20. LIGO/Virgo/KAGRA S230729z: Identification of a GW compact binary merger candidate
  21. IceCube-230727A: Upper limits from a search for additional neutrino events in IceCube
  22. GRB 230728A: BOOTES-1 optical upper limit
  23. GRB 230728A: Fermi GBM Observation
  24. GRB 230728A: LCOGT Optical Upper Limit
  25. GRB 230728A: Swift/UVOT Upper Limits
  26. GRB 230728A: Swift-XRT refined Analysis
  27. GRB 230728A: Enhanced Swift-XRT position
  28. GRB 230728A: NOT optical observations and possible host galaxy
  29. IceCube-230724A: No counterparts from the Zwicky Transient Facility
  30. GRB 230727A: AstroSat CZTI detection
  31. GRB 230728A: Swift detection of a burst
  32. Swift GRB230728.12: Global MASTER-Net observations report
  33. GRB 230727A: Swift/BAT-GUANO detection of a burst
  34. Fermi-LAT gamma-ray observations of IceCube-230725A
  35. Fermi-LAT gamma-ray observations of IceCube-230724A
  36. Fermi trigger No 712143685: Global MASTER-Net observations report
  37. IceCube-230727A - IceCube observation of a high-energy neutrino candidate track-like event
  38. GRB 230727A: Fermi GBM Final Real-time Localization
  39. IceCube-230725A: Upper limits from a search for additional neutrino events in IceCube
  40. IceCube-230724A: Upper limits from a search for additional neutrino events in IceCube
  41. Integral GRB230726.26: Global MASTER-Net observations report
  42. GRB 230723B: Further CAHA observations and host galaxy detection
  43. LIGO/Virgo/KAGRA S230726a: Updated Sky localization
  44. Konus-Wind detection of GRB 230723A
  45. GRB 230723B: MITSuME Akeno optical afterglow candidate detection
  46. GRB 230723B: ATCA rapid radio follow-up
  47. LIGO/Virgo/KAGRA S230726b: one counterpart neutrino candidate from IceCube neutrino searches
  48. IceCube-230724A - IceCube observation of a high-energy neutrino candidate track-like event
  49. LIGO/Virgo/KAGRA S230726a: Identification of a GW compact binary merger candidate
  50. IBAS trigger number 10337: not a real GRB
  51. Integral GRB230725.99: Global MASTER-Net observations report
  52. IceCube-230725A - IceCube observation of a high-energy neutrino candidate track-like event
  53. IceCube Alert 230725.90: Global MASTER-Net observations report
  54. GRB 230723B: GAD Observatory, La Spezia, Italy upper limit
  55. IPN triangulation of GRB 230723A (short)
  56. Fermi Gamma-ray Burst Monitor trigger 711982704/230725540 is not a GRB
  57. GRB 230725B: Fermi GBM Final Real-time Localization
  58. GRB 230725A: Fermi GBM Final Real-time Localization
  59. GRB 230723B: Leavitt Observatory upper limit
  60. GRB 230723B: Osservatorio Astronomico Nastro Verde upper limit
  61. GRB 230723B: Montarrenti Observatory upper limit
  62. GRB 230723B: Optical afterglow candidate from CAHA
  63. GRB 230723B: Bassano Bresciano Observatory upper limit
  64. GRB 230723B: Fermi GBM observation
  65. GRB 230723B: Swift-XRT refined Analysis
  66. GRB 230723B: non-detections from Observatoire de Haute-Provence
  67. IceCube Alert 230724.08: Global MASTER-Net observations report
  68. LIGO/Virgo/KAGRA S230723ac: Updated Sky localization
  69. Fermi trigger No 711853834: Global MASTER-Net observations report
  70. GRB 230724A: Fermi GBM Final Real-time Localization
  71. Fermi trigger No 711805358: Global MASTER-Net observations report
  72. GRB 230723B: Optical limit from CAHA
  73. GRB 230723B: Swift/UVOT Upper Limits
  74. Swift GRB 230723B: Global MASTER-Net observations report
  75. Swift-XRT position for GRB 230723B
  76. GRB 230723A: AGILE/MCAL detection
  77. GRB 230723B: Swift-XRT observations
  78. LIGO/Virgo/KAGRA S230723ac: Identification of a GW compact binary merger candidate
  79. GRB 230723B: Swift detection of a burst
  80. Fermi GRB 230723A: Global MASTER-Net observations report
  81. GRB 230723A: Fermi GBM Final Real-time Localization
  82. Swift GRB230720.30: Global MASTER-Net observations report
  83. IPN triangulation of GRB 230715D
  84. Swift Trigger 1180063 is not a GRB
  85. Swift Trigger 1180060 is not a GRB
  86. Swift Trigger 1180055 is not a GRB
  87. GRB 230718A: Final Localization Correction
  88. GRB 230718A: Fermi GBM Final Real-time Localization
  89. Fermi Gamma-ray Burst Monitor trigger 711329677/230717982 is not a GRB
  90. IPN triangulation of GRB 230712C (short)
  91. IPN triangulation of GRB 230712A (short)
  92. LIGO/Virgo/KAGRA S230708z: Updated Sky localization
  93. GRB 230717A: Fermi GBM Final Real-time Localization
  94. LIGO/Virgo/KAGRA S230715bw: Retraction of GW compact binary merger candidate
  95. Fermi trigger No 711088412: Global MASTER-Net observations report
  96. GRB 230715A: Fermi GBM Final Real-time Localization
  97. Fermi GRB 230713A: Global MASTER-Net observations report
  98. IceCube-230707A : MAXI upper limit and NICER follow-up observation of Swift J1753.5-0127
  99. GRB 230713A: Fermi GBM Final Real-time Localization
  100. LIGO/Virgo/KAGRA S230709bi: Updated Sky localization

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