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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 230919A: Fermi GBM Observation
  2. Correction to Fermi GBM Statement for Trigger 716527670/230916144
  3. Fermi GBM Statement for Trigger 716527670/230916144
  4. GRB 230919A: Swift/BAT-GUANO detection of a possibly short burst outside the coded FOV
  5. LIGO/Virgo/KAGRA S230920al: Updated Sky localization
  6. LIGO/Virgo/KAGRA S230919bj: Updated Sky localization
  7. transient AT2023sva: imaging and spectroscopic observations from MISTRAL at Observatoire de Haute-Provence
  8. GRB 230812B : optical observations from MISTRAL at Observatoire de Haute-Provence
  9. GRB 230919A: AstroSat CZTI detection
  10. LIGO/Virgo/KAGRA S230920al: Identification of a GW compact binary merger candidate
  11. AT2023sva: redshift from OSIRIS+/GTC of the ZTF afterglow
  12. LIGO/Virgo/KAGRA S230919bj: Identification of a GW compact binary merger candidate
  13. GRB 230918B: GOTO detection of a fast-rising transient in the GBM localisation region
  14. GRB 230919A: Fermi GBM Final Real-time Localization
  15. LIGO/Virgo S230917af: Swift XRT observations, 6 X-ray sources
  16. Detection of self-absorbed radio emission from GRB 230812B with the JVLA + uGMRT
  17. GRB 230918B: Fermi GBM Final Real-time Localization
  18. GRB 230918A (short): Glowbug gamma-ray detection
  19. GRB 230916B: Glowbug gamma-ray detection
  20. AT 2023sva: NOT observations of the ZTF candidate afterglow
  21. ZTF and SEDM Observations of the Candidate Optical Afterglow AT 2023sva
  22. GRB 230915A: Fermi GBM observation
  23. LIGO/Virgo/KAGRA S230918aq: Retraction of GW compact binary merger candidate
  24. GRB 230812B: Radio observations with the uGMRT
  25. GRB 230918A: Fermi GBM Final Real-time Localization
  26. GRB 230917A: AstroSat CZTI detection
  27. Swift Triggers 1192480, 1192481, 1192482 and 1192483 are not astrophysical events
  28. LIGO/Virgo/KAGRA S230917af: MAXI/GSC observations
  29. GRB 230915B: Glowbug gamma-ray detection
  30. GRB 230916A: NuSTAR Discovery of Prompt Emission from a Potential GRB
  31. GRB 230911A: Fermi GBM Observation
  32. Swift GRB230916.18: Global MASTER-Net observations report
  33. Fermi trigger No 716572242: Global MASTER-Net observations report
  34. LIGO/Virgo/KAGRA S230904n: Correction of the coordinates of the ZTF candidate counterpart
  35. Fermi trigger No 716544961: Global MASTER-Net observations report
  36. Fermi-LAT gamma-ray observations of IceCube-230914A
  37. GRB 230915A: Swift/BAT-GUANO detection of a burst
  38. LIGO/Virgo/KAGRA S230914ak: Upper limits from Swift/BAT-GUANO
  39. GRB 230911D: GRBAlpha detection
  40. Swift GRB230916.19: Global MASTER-Net observations report
  41. Swift GRB230916.18: Global MASTER-Net observations report
  42. Swift Triggers 1192234, 1192235 and 1192236 are not astrophysical events
  43. Swift GRB230916.13: Global MASTER-Net observations report
  44. Swift GRB230916.12: Global MASTER-Net observations report
  45. Swift GRB230916.11: Global MASTER-Net observations report
  46. Swift Trigger 1192233 is not a GRB
  47. GRB 230906A: optical counterpart
  48. IceCube-230914A: Upper limits from a search for additional neutrino events in IceCube
  49. GRB 230911A: Swift-XRT afterglow detection
  50. Fermi trigger No 716449174: Global MASTER-Net observations report
  51. GRB 230913A: CALET Gamma-Ray Burst Monitor detection
  52. IceCube Alert 230914.22: Global MASTER-Net observations report
  53. Swift Trigger 1192088 is not an astrophysical event
  54. Fermi trigger No 716419312: Global MASTER-Net observations report
  55. GRB 230913A: Glowbug gamma-ray detection
  56. LIGO/Virgo/KAGRA S230914ak: Updated Sky localization
  57. GRB 230812B: Bad Time Intervals for Fermi GBM data
  58. IceCube-230914A - IceCube observation of a high-energy neutrino candidate track-like event
  59. LIGO/Virgo/KAGRA S230914ak: Identification of a GW compact binary merger candidate
  60. Swift Trigger 1191994 is not an astrophysical event
  61. Swift GRB230913.70: Global MASTER-Net observations report
  62. GRB 230913A: Fermi GBM Observation
  63. LIGO/Virgo/KAGRA S230904n: One ZTF candidate counterpart to coincident neutrino event
  64. Swift Trigger 1191904 is not a GRB
  65. Swift GRB230913.70: Global MASTER-Net observations report
  66. Swift Trigger 1191903 is not an astrophysical event
  67. GRB 230911A: Swift ToO observations
  68. GRB 230913A: Swift/BAT-GUANO arcminute localization of a burst
  69. Fermi GRB 230913A: Global MASTER-Net observations report
  70. GRB 230911A: GOTO optical counterpart candidate
  71. GRB 230913A: Fermi GBM Final Real-time Localization
  72. GRB 230908A: CALET Gamma-Ray Burst Monitor detection
  73. GRB 230911D: NuSTAR Detection of Prompt Emission
  74. GRB 230911B: AstroSat CZTI detection
  75. GRB 230911C: Swift-XRT refined Analysis
  76. GRB 230911C: Swift-BAT refined analysis
  77. LIGO/Virgo/KAGRA S230911ae: Updated Sky localization
  78. GRB230911C: BOOTES-6/DPRT optical upper limit
  79. GRB 230906A: Chandra detection of the X-ray afterglow
  80. Swift GRB 230911C: Global MASTER-Net observations report
  81. GRB 230911D: Fermi GBM observation
  82. IPN triangulation of GRB 230911D (long)
  83. GRB 230911D: Fermi-LAT detection
  84. GRB230911C: LCOGT Optical Upper Limits
  85. LIGO/Virgo/KAGRA S230911ae: Identification of a GW compact binary merger candidate
  86. GRB 230911C: Swift/UVOT Upper Limits
  87. GRB 230911B: GRBAlpha and VZLUSAT-2 joint detection
  88. Fermi trigger No 716145795: Global MASTER-Net observations report
  89. GRB 230911C: GOTO optical upper limits
  90. GRB 230908A: Swift/BAT-GUANO detection of a long burst outside the coded FOV
  91. GRB 230911B: correction to the KW GCN 34659
  92. Konus-Wind detection of GRB 230811D
  93. GRB 230911C: Enhanced Swift-XRT position
  94. GRB 230911D: BALROG localization (Fermi Trigger 716111594/ GRB 230911329)
  95. GRB 230911D: Fermi GBM Final Localization
  96. GRB 230911C: Swift detection of a burst
  97. Fermi GRB 230911B: Global MASTER-Net observations report
  98. GRB 230911B: Fermi GBM Final Real-time Localization
  99. GRB 230911A: Fermi GBM Final Real-time Localization
  100. GRB 230906A: BlackGEM upper limits

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