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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 230802A: Fermi GBM observation
  2. GRB 230802A: Swift-BAT refined analysis
  3. GRB 230804A: Fermi GBM Final Real-time Localization
  4. Fermi trigger No 712798043: Global MASTER-Net observations report
  5. IPN triangulation of GRB 230803A
  6. GRB 230802A: Swift/UVOT Upper Limits
  7. GRB 230803A: AstroSat CZTI detection
  8. LIGO/Virgo/KAGRA S230802aq: AstroSat CZTI non-detection and upper limits
  9. Fermi trigger No 712718833: Global MASTER-Net observations report
  10. GRB 230803A: Fermi GBM Final Real-time Localization
  11. Fermi trigger No 712713532: Global MASTER-Net observations report
  12. Fermi trigger No 712651827: Global MASTER-Net observations report
  13. GRB 230802B: Fermi GBM Final Localization
  14. Swift GRB 230802A: Global MASTER-Net observations report
  15. GRB 230802A: BOOTES-5/JGT optical upper limit
  16. LIGO/Virgo/KAGRA S230802aq: Upper limits from Fermi-GBM Observations
  17. GRB 230802A: Swift-XRT refined Analysis
  18. GRB 230802A: Enhanced Swift-XRT position
  19. LIGO/Virgo S230802aq: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  20. LIGO/Virgo/KAGRA S230802aq: Coverage and upper limits from MAXI/GSC observations
  21. LIGO/Virgo/KAGRA S230802aq: Identification of a GW compact binary merger candidate
  22. GRB 230802A: Swift detection of a burst
  23. IceCube-230724A: JCMT/SCUBA-2 submm observations
  24. IceCube-230707A: JCMT/SCUBA-2 submm observations
  25. LIGO/Virgo/KAGRA S230731an: Upper limits from Swift/BAT-GUANO
  26. GRB 230723A: SPT-3G millimeter-band transient event inconsistent with IPN position
  27. LIGO/Virgo/KAGRA S230731an: AstroSat CZTI non-detection and upper limits
  28. LIGO/Virgo/KAGRA S230731an: not observable by Fermi-GBM
  29. LIGO/Virgo/KAGRA S230731an: Updated Sky Localization and EM Bright Classification, and Correction to Source Classification
  30. GRB 230731A: Fermi GBM Final Real-time Localization
  31. LIGO/Virgo/KAGRA S230731an: Coverage and upper limits from MAXI/GSC observations
  32. LIGO/Virgo/KAGRA S230731an: Identification of a GW compact binary merger candidate
  33. LIGO/Virgo/KAGRA S230729z: Updated Sky localization
  34. GRB 230723A: Detection of candidate millimeter-band radiation by SPT-3G
  35. Fermi trigger No 712390645: Global MASTER-Net observations report
  36. GRB 230728A: Swift-BAT refined analysis
  37. Fermi-LAT gamma-ray observations of IceCube-230727A
  38. GRB 230723B: Swift-BAT refined analysis
  39. Fermi trigger No 712306969: Global MASTER-Net observations report
  40. GRB 230723B: MITSuME Ishigaki optical observation
  41. IceCube-230727A: No candidates from the Zwicky Transient Facility
  42. LIGO/Virgo/KAGRA S230729z: Identification of a GW compact binary merger candidate
  43. IceCube-230727A: Upper limits from a search for additional neutrino events in IceCube
  44. GRB 230728A: BOOTES-1 optical upper limit
  45. GRB 230728A: Fermi GBM Observation
  46. GRB 230728A: LCOGT Optical Upper Limit
  47. GRB 230728A: Swift/UVOT Upper Limits
  48. GRB 230728A: Swift-XRT refined Analysis
  49. GRB 230728A: Enhanced Swift-XRT position
  50. GRB 230728A: NOT optical observations and possible host galaxy
  51. IceCube-230724A: No counterparts from the Zwicky Transient Facility
  52. GRB 230727A: AstroSat CZTI detection
  53. GRB 230728A: Swift detection of a burst
  54. Swift GRB230728.12: Global MASTER-Net observations report
  55. GRB 230727A: Swift/BAT-GUANO detection of a burst
  56. Fermi-LAT gamma-ray observations of IceCube-230725A
  57. Fermi-LAT gamma-ray observations of IceCube-230724A
  58. Fermi trigger No 712143685: Global MASTER-Net observations report
  59. IceCube-230727A - IceCube observation of a high-energy neutrino candidate track-like event
  60. GRB 230727A: Fermi GBM Final Real-time Localization
  61. IceCube-230725A: Upper limits from a search for additional neutrino events in IceCube
  62. IceCube-230724A: Upper limits from a search for additional neutrino events in IceCube
  63. Integral GRB230726.26: Global MASTER-Net observations report
  64. GRB 230723B: Further CAHA observations and host galaxy detection
  65. LIGO/Virgo/KAGRA S230726a: Updated Sky localization
  66. Konus-Wind detection of GRB 230723A
  67. GRB 230723B: MITSuME Akeno optical afterglow candidate detection
  68. GRB 230723B: ATCA rapid radio follow-up
  69. LIGO/Virgo/KAGRA S230726b: one counterpart neutrino candidate from IceCube neutrino searches
  70. IceCube-230724A - IceCube observation of a high-energy neutrino candidate track-like event
  71. LIGO/Virgo/KAGRA S230726a: Identification of a GW compact binary merger candidate
  72. IBAS trigger number 10337: not a real GRB
  73. Integral GRB230725.99: Global MASTER-Net observations report
  74. IceCube-230725A - IceCube observation of a high-energy neutrino candidate track-like event
  75. IceCube Alert 230725.90: Global MASTER-Net observations report
  76. GRB 230723B: GAD Observatory, La Spezia, Italy upper limit
  77. IPN triangulation of GRB 230723A (short)
  78. Fermi Gamma-ray Burst Monitor trigger 711982704/230725540 is not a GRB
  79. GRB 230725B: Fermi GBM Final Real-time Localization
  80. GRB 230725A: Fermi GBM Final Real-time Localization
  81. GRB 230723B: Leavitt Observatory upper limit
  82. GRB 230723B: Osservatorio Astronomico Nastro Verde upper limit
  83. GRB 230723B: Montarrenti Observatory upper limit
  84. GRB 230723B: Optical afterglow candidate from CAHA
  85. GRB 230723B: Bassano Bresciano Observatory upper limit
  86. GRB 230723B: Fermi GBM observation
  87. GRB 230723B: Swift-XRT refined Analysis
  88. GRB 230723B: non-detections from Observatoire de Haute-Provence
  89. IceCube Alert 230724.08: Global MASTER-Net observations report
  90. LIGO/Virgo/KAGRA S230723ac: Updated Sky localization
  91. Fermi trigger No 711853834: Global MASTER-Net observations report
  92. GRB 230724A: Fermi GBM Final Real-time Localization
  93. Fermi trigger No 711805358: Global MASTER-Net observations report
  94. GRB 230723B: Optical limit from CAHA
  95. GRB 230723B: Swift/UVOT Upper Limits
  96. Swift GRB 230723B: Global MASTER-Net observations report
  97. Swift-XRT position for GRB 230723B
  98. GRB 230723A: AGILE/MCAL detection
  99. GRB 230723B: Swift-XRT observations
  100. LIGO/Virgo/KAGRA S230723ac: Identification of a GW compact binary merger candidate

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