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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. Fermi GRB 230812B: MASTER optical counterpart
  2. GRB 230812B: KAIT Optical Afterglow Candidate
  3. GRB 230812B: Improved Swift/XRT localization
  4. GRB 230812B: Preliminary Swift/XRT localization
  5. GRB 230812B: Fermi-LAT detection
  6. GRB 230812B: Fermi GBM Observation of a very bright burst
  7. LAT GRB230812.79: Global MASTER-Net observations report
  8. Fermi GRB 230812B: Global MASTER-Net observations report
  9. GRB 230812B: Tiled Swift observations
  10. GRB 230812B: Fermi GBM detection of an extremely bright GRB
  11. GRB 230812B: Fermi GBM Final Real-time Localization
  12. ZTF23aaoohpy/AT2023lcr: JWST spectroscopy confirmation of an associated type Ic-BL supernova
  13. Fermi trigger No 713525317: Global MASTER-Net observations report
  14. GRB 230812A: Fermi GBM Final Real-time Localization
  15. LIGO/Virgo/KAGRA S230811n: Updated Sky localization
  16. GRB 230808A: Fermi GBM Detection
  17. LIGO/Virgo/KAGRA S230811n: Identification of a GW compact binary merger candidate
  18. GRB 230805B: Swift-BAT refined analysis
  19. LIGO/Virgo/KAGRA S230810af: Retraction of GW compact binary merger candidate
  20. GRB 230805B: Iota Scorpii Observatory, La Spezia, Italy upper limit
  21. GRB 230805B: AstroSat CZTI detection
  22. GRB 230808A: Swift/BAT-GUANO detection of a burst
  23. Fermi trigger No 713136868: Global MASTER-Net observations report
  24. GRB 230808B: Fermi GBM Final Real-time Localization
  25. The Fermi GBM Trigger 713134237 / 230807868 is not associated with LIGO/Virgo/KAGRA S230807f.
  26. Fermi trigger No 713205976: Global MASTER-Net observations report
  27. ZTF23aaoohpy/AT2023lcr: JWST observations consistent with the presence of a supernova
  28. GRB 230808A: Fermi GBM Final Real-time Localization
  29. GRB 230805B : MITSuME Akeno optical upper limits
  30. LIGO/Virgo/KAGRA S230808i: retraction of a GW unmodeled transient candidate
  31. LIGO/Virgo/KAGRA S230808i: Identification of a GW unmodeled transient candidate
  32. LIGO/Virgo/KAGRA S230807f: Updated Sky localization and EM Bright Classification
  33. transient SPT-SVJ025406.5-702837: ATCA follow-up observations
  34. Fermi GRB 230807A: Global MASTER-Net observations report
  35. Fermi trigger No 713134237: Global MASTER-Net observations report
  36. GRB 230807A: Fermi GBM Final Real-time Localization
  37. LIGO/Virgo/KAGRA S230807f: Identification of a GW compact binary merger candidate
  38. LIGO/Virgo/KAGRA S230805x: Upper limits from Swift/BAT-GUANO
  39. Konus-Wind detection of GRB 230803A
  40. GRB 230805B: Fermi GBM observation
  41. GRB 230805B : OHP/T193 optical upper limit
  42. LIGO/Virgo/KAGRA S230806ak: Updated Sky localization and EM Bright Classification
  43. GRB 230806A: Fermi GBM Final Localization
  44. GRB 230805B: Enhanced Swift-XRT position
  45. LIGO/Virgo/KAGRA S230806ak: Identification of a GW compact binary merger candidate
  46. GRB 230805B: Swift/UVOT Upper Limits
  47. Fermi trigger No 712991593: Global MASTER-Net observations report
  48. GRB 230805B: Bassano Bresciano observatory upper limit
  49. Fermi trigger No 712987357: Global MASTER-Net observations report
  50. GRB 230805B: BOOTES-6/DPRT optical upper limit and 1.5m OSN detection
  51. GRB 230805B: NOT optical afterglow confirmation
  52. GRB 230805B: Swift-XRT refined Analysis
  53. Fermi GRB 230805A: Global MASTER-Net observations report
  54. GRB 230805B: SAO RAS optical observations
  55. Fermi trigger No 712927418: Global MASTER-Net observations report
  56. Swift GRB 230805B: Global MASTER-Net observations report
  57. LIGO/Virgo/KAGRA S230805x: Updated Sky localization
  58. GRB 230805B: Swift detection of a burst
  59. GRB 230805A: Fermi GBM Final Real-time Localization
  60. LIGO/Virgo/KAGRA S230805x: Identification of a GW compact binary merger candidate
  61. LIGO/Virgo/KAGRA S230802aq: Updated Sky localization and EM Bright Classification
  62. GRB 230802B: AstroSat CZTI detection
  63. GRB 230802A: Fermi GBM observation
  64. GRB 230802A: Swift-BAT refined analysis
  65. GRB 230804A: Fermi GBM Final Real-time Localization
  66. Fermi trigger No 712798043: Global MASTER-Net observations report
  67. IPN triangulation of GRB 230803A
  68. GRB 230802A: Swift/UVOT Upper Limits
  69. GRB 230803A: AstroSat CZTI detection
  70. LIGO/Virgo/KAGRA S230802aq: AstroSat CZTI non-detection and upper limits
  71. Fermi trigger No 712718833: Global MASTER-Net observations report
  72. GRB 230803A: Fermi GBM Final Real-time Localization
  73. Fermi trigger No 712713532: Global MASTER-Net observations report
  74. Fermi trigger No 712651827: Global MASTER-Net observations report
  75. GRB 230802B: Fermi GBM Final Localization
  76. Swift GRB 230802A: Global MASTER-Net observations report
  77. GRB 230802A: BOOTES-5/JGT optical upper limit
  78. LIGO/Virgo/KAGRA S230802aq: Upper limits from Fermi-GBM Observations
  79. GRB 230802A: Swift-XRT refined Analysis
  80. GRB 230802A: Enhanced Swift-XRT position
  81. LIGO/Virgo S230802aq: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  82. LIGO/Virgo/KAGRA S230802aq: Coverage and upper limits from MAXI/GSC observations
  83. LIGO/Virgo/KAGRA S230802aq: Identification of a GW compact binary merger candidate
  84. GRB 230802A: Swift detection of a burst
  85. IceCube-230724A: JCMT/SCUBA-2 submm observations
  86. IceCube-230707A: JCMT/SCUBA-2 submm observations
  87. LIGO/Virgo/KAGRA S230731an: Upper limits from Swift/BAT-GUANO
  88. GRB 230723A: SPT-3G millimeter-band transient event inconsistent with IPN position
  89. LIGO/Virgo/KAGRA S230731an: AstroSat CZTI non-detection and upper limits
  90. LIGO/Virgo/KAGRA S230731an: not observable by Fermi-GBM
  91. LIGO/Virgo/KAGRA S230731an: Updated Sky Localization and EM Bright Classification, and Correction to Source Classification
  92. GRB 230731A: Fermi GBM Final Real-time Localization
  93. LIGO/Virgo/KAGRA S230731an: Coverage and upper limits from MAXI/GSC observations
  94. LIGO/Virgo/KAGRA S230731an: Identification of a GW compact binary merger candidate
  95. LIGO/Virgo/KAGRA S230729z: Updated Sky localization
  96. GRB 230723A: Detection of candidate millimeter-band radiation by SPT-3G
  97. Fermi trigger No 712390645: Global MASTER-Net observations report
  98. GRB 230728A: Swift-BAT refined analysis
  99. Fermi-LAT gamma-ray observations of IceCube-230727A
  100. GRB 230723B: Swift-BAT refined analysis

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