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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 241018A: Detection of a bright long GRB by SVOM
  2. GRB 241017A: Swift-XRT observations
  3. GRB241017a: Liverpool Telescope observations of XRT uncatalogued sources
  4. GRB 241001A: EP-FXT afterglow detection
  5. GRB 241017A: GROWTH-India Telescope optical upper limit
  6. GRB241017A: TOO Observations by SVOM/MXT
  7. GRB 241016B: Swift/BAT-GUANO localization skymap of a short burst
  8. GRB 241017A: J-band upper limit from WINTER
  9. Fermi trigger No 750788395: Global MASTER-Net observations report
  10. GRB 241016B: SVOM/GRM observation
  11. GRB241016C: Fermi GBM Final Localization
  12. Fermi Gamma-ray Burst Monitor trigger 750792698/241016730 is not a GRB
  13. GRB 241017A: Swift ToO observations
  14. GRB 241017A : Detection of a weak and soft long duration GRB by SVOM/ECLAIRs
  15. Fermi GRB 241016B: Global MASTER-Net observations report
  16. GRB 241016B: Fermi GBM Final Localization
  17. Fermi GRB 241016A: Global MASTER-Net observations report
  18. GRB 241016A: Fermi GBM Final Real-time Localization
  19. IceCube alert 139977_2910365 retraction
  20. IceCube Alert 241016.04: Global MASTER-Net observations report
  21. GRB 241010A: Swift-BAT refined analysis
  22. GRB 241013B: Fermi GBM Observation
  23. GRB 241013B: Swift/BAT-GUANO localization skymap of a burst
  24. GRB 241013A: Fermi GBM Observation
  25. GRB 240916A: radio detection with the VLA
  26. GRB241013A: REM observations
  27. GRB 241009A: LCO optical upper limits
  28. GRB 241013B: SVOM/GRM observation
  29. Fermi GRB 241013B: Global MASTER-Net observations report
  30. Integral GRB241013.04: Global MASTER-Net observations report
  31. GRB 241013B: Fermi GBM Final Real-time Localization
  32. GRB 241013A: a long GRB detected by INTEGRAL
  33. GRB 241013A: Fermi GBM Final Real-time Localization
  34. LIGO/Virgo/KAGRA S241009em: Updated Sky localization
  35. LIGO/Virgo/KAGRA S241011k: Updated Sky localization
  36. LIGO/Virgo/KAGRA S241011k: NED Galaxies in the Localization Volume
  37. LIGO/Virgo/KAGRA S241011k: Identification of a GW compact binary merger candidate
  38. Fermi Gamma-ray Burst Monitor GRB trigger 750372658/241011869 (GRB 241011A) is not a GRB
  39. GRB 241011A: Fermi GBM Final Real-time Localization
  40. GRB 241009A: GRANDMA optical upper limits
  41. GRB 241009A: Swift-XRT afterglow detection
  42. GRB 241010A: JinShan optical observations and potential host galaxy
  43. GRB 241006A: ATCA Radio Upper Limits
  44. GRB 241010A: Swift-XRT refined Analysis
  45. LIGO/Virgo/KAGRA S241007bw: Updated Sky localization
  46. Fermi trigger No 750211959: Global MASTER-Net observations report
  47. Fermi Gamma-ray Burst Monitor trigger 750303285/241011066 is not a GRB
  48. Fermi Gamma-ray Burst Monitor trigger 750291012/241010924 is not a GRB
  49. Swift GRB 241010A: Global MASTER-Net observations report
  50. Fermi trigger No 750291012: Global MASTER-Net observations report
  51. GRB 241010A: J-band observations with WINTER
  52. LIGO/Virgo/KAGRA S241009an: Updated Sky localization
  53. Fermi GRB 241010B: Global MASTER-Net observations report
  54. GRB 241010B: Fermi GBM Final Real-time Localization
  55. IceCube-241006A: Upper limits from a search for additional neutrino events in IceCube
  56. GRB 241010A: Enhanced Swift-XRT position
  57. GRB 241010A: LCO optical observations
  58. GRB 241010A: Swift detection of a burst with an optical counterpart
  59. Fermi-LAT Gamma-ray Observations of IceCube-241006A
  60. GRB 241006A: Swift-BAT refined analysis
  61. GRB 241009A: Swift ToO observations
  62. LIGO/Virgo/KAGRA S241009l: Updated Sky localization
  63. LIGO/Virgo/KAGRA S241009em: Identification of a GW compact binary merger candidate
  64. GRB 241009A : Detection of a long duration GRB by SVOM/ECLAIRs
  65. GRB 241008A: Fermi GBM Observation
  66. GRB 241008A: Fermi-LAT detection
  67. GRB 241002B: Swift-XRT afterglow detection
  68. LIGO/Virgo/KAGRA S241009an: Identification of a GW compact binary merger candidate
  69. GRB 241002A: NOT optical upper limits
  70. LIGO/Virgo/KAGRA S241009l: Identification of a GW compact binary merger candidate
  71. Fermi GRB 241008A: Global MASTER-Net observations report
  72. GRB 241008A: BALROG localization (Fermi Trigger 750117609 / GRB 241008917)
  73. GRB 241008A: Fermi GBM Final Real-time Localization
  74. IceCube-241006A: No candidates from the Zwicky Transient Facility
  75. GRB 241006A: GRANDMA optical upper limits
  76. EP240930a / GRB 240930B: CrAO ZTSH optical upper limit
  77. GRB 241002B: PRIME near-infrared detection in 3rd epoch
  78. Fermi-LAT Gamma-ray Observations of NuEm-240926A
  79. GRB 240910A: LBT optical observations
  80. EP trigger ID 01709065118: KAIT confirmation of the stellar flare
  81. GRB 241006A: Swift-XRT refined Analysis
  82. GRB 240821A: Host galaxy redshift from VLT/X-shooter
  83. GRB 241006A: PRIME near-infrared upper limits
  84. GRB 241006A: Swift/UVOT Upper Limits
  85. GRB 241006A: SVOM/VT follow-up and optical upper limit
  86. LIGO/Virgo/KAGRA S241007bw: Identification of a GW compact binary merger candidate
  87. IceCube Alert 241006.94: Global MASTER-Net observations report
  88. GRB 241001A: Swift-XRT afterglow detection
  89. GRB 241006A: Enhanced Swift-XRT position
  90. IceCube-241006A - IceCube observation of a high-energy neutrino candidate track-like event
  91. GRB 241006A: Swift detection of a burst
  92. Swift GRB241006.91: Global MASTER-Net observations report
  93. GRB 240930B: SVOM/C-GFT optical upper limit
  94. LIGO/Virgo/KAGRA S241006k: Identification of a GW compact binary merger candidate
  95. LIGO/Virgo/KAGRA S241005bo: Retraction of GW compact binary merger candidate
  96. Fermi trigger No 749721670: Global MASTER-Net observations report
  97. GRB 241004A: SVOM/GRM observation
  98. EP trigger ID 01709065118: the X-ray transient is likely a stellar flare event
  99. GRB 240930B / EP 240930a: SVOM/GRM observation
  100. GRB 241001A : ECLAIRs spectral analysis and XRF classification

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