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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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').
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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.

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subject:"Swift"
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24454 results found.

  1. LIGO/Virgo/KAGRA S250118az: Updated Sky localization
  2. LIGO/Virgo/KAGRA S250208ad: Updated Sky localization
  3. GRB 250206A: EIRSAT-1 GMOD Detection
  4. LIGO/Virgo/KAGRA S250206dm: (Update-7) NED Galaxies in the Localization Volume
  5. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
  6. GRB 250206A: Fermi-LAT detection
  7. GRB 250207B: Swift-XRT observations
  8. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  9. IceCube-250203A: No transient candidates from the Zwicky Transient Facility
  10. LIGO/Virgo/KAGRA S250206dm: Spectroscopic Classification of AT2025bay and AT2025baz with Keck I/LRIS
  11. LIGO/Virgo/KAGRA S250206dm: Candidates from the Zwicky Transient Facility
  12. GRB 250208A: Fermi GBM Final Real-time Localization
  13. EP250207a: EP-WXT detection and XRT follow-up observation
  14. LIGO/Virgo/KAGRA S250208ad: Identification of a GW compact binary merger candidate
  15. LIGO/Virgo/KAGRA S250206dm: MMT galaxy targeted observations
  16. GRB 250207A: Swift-XRT refined Analysis
  17. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A & "Time Machine" Effect.
  18. CHIME/FRB source FRB 20250206A detected less than 1 minute after LIGO-Virgo-Kagra (LVK) S250206dm, however the probability of spatial coincidence is order 0.1%
  19. LIGO/Virgo/KAGRA S250206dm: GOTO counterpart search update - AT2025bar
  20. EP-WXT trigger 01709131361 / LIGO/Virgo/KAGRA S250206dm: FTW optical and NIR observations
  21. GRB 250129A: ABObservatory SLOAN r’ afterglow detection
  22. GRB 250207A: REM IR afterglow detection
  23. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits
  24. LIGO/Virgo/KAGRA S250207bg: NED Galaxies in the Localization Volume
  25. Konus-Wind detection of GRB 250204B
  26. IceCube-250207A - IceCube observation of a high-energy neutrino candidate track-like event
  27. GRB 250207A: REM optical afterglow detection
  28. LIGO/Virgo/KAGRA S250207bg: Identification of a GW compact binary merger candidate
  29. LIGO/Virgo/KAGRA S250206dm:GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  30. LIGO/Virgo/KAGRA S250206dm: GOTO observations of optical candidates AT 2025azn and AT 2025azm
  31. LIGO/Virgo/KAGRA S250206dm: SOAR galaxy targeted observations
  32. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS observations of AT2025azm and AT2025azn
  33. LIGO/Virgo/KAGRA S250206dm: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  34. LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
  35. LIGO/Virgo/KAGRA S250206dm: Updated-6 NED Galaxies in the Localization Volume
  36. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  37. LIGO/Virgo/KAGRA S250206dm: Upper limits from Fermi-GBM Observations
  38. GRB 250207A: Fermi GBM Final Real-time Localization
  39. Fermi-LAT Gamma-ray Observations of IceCube-250203A
  40. LIGO/Virgo/KAGRA S250206dm: Coverage and upper limits from MAXI/GSC observations
  41. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  42. LIGO/Virgo/KAGRA S250206dm: Updated NED Galaxies in the Localization Volume
  43. LIGO/Virgo/KAGRA S250206dm: Two counterpart neutrino candidates from IceCube neutrino searches
  44. LIGO/Virgo/KAGRA S250206dm: Identification of a GW compact binary merger candidate
  45. LIGO/Virgo/KAGRA S250206dm: NED Galaxies in the Localization Volume
  46. GRB 250206A: BALROG localization (Fermi Trigger 760564296 / GRB 250206827)
  47. GRB 250206A: Fermi GBM Final Real-time Localization
  48. GRB 250205A: Fermi GBM Observation
  49. GRB 250205A: REM NIR upper limit
  50. LIGO/Virgo/KAGRA S250205ee: Updated Sky localization and Source Classification
  51. EP250205a/GRB 250205A: correction to the source localization
  52. EP250205a/GRB 250205A: Einstein Probe observation
  53. GRB 250127C: SVOM/GRM observation of a burst
  54. GRB250205A: SVOM/VT optical afterglow detection
  55. GRB 250205A: GOTO optical upper limits
  56. LIGO/Virgo/KAGRA S250205ee: Identification of a GW compact binary merger candidate
  57. GRB 250205A: SVOM detection of a burst
  58. LIGO/Virgo/KAGRA S250205bk: NED Galaxies in the Localization Volume
  59. Konus-Wind detection of GRB 250201A
  60. IPN triangulation of GRB 250201A
  61. LIGO/Virgo/KAGRA S250205bk: Updated Sky localization
  62. Konus-Wind detection of GRB 250202B
  63. LIGO/Virgo/KAGRA S250205bk: Identification of a GW compact binary merger candidate
  64. GRB 250129A: Swift-BAT refined analysis
  65. EP 250108A: Upper limits from Fermi-GBM Observations
  66. IPN triangulation of GRB 250204B (short/hard)
  67. IPN triangulation of GRB 250202B
  68. LIGO/Virgo/KAGRA S250204ax: Updated Sky localization
  69. GRB 250204B: Fermi GBM Final Localization
  70. GRB 250129A: LCO late afterglow detection
  71. GRB 250204A: Fermi GBM Final Real-time Localization
  72. LIGO/Virgo/KAGRA S250204ax: Identification of a GW compact binary merger candidate
  73. GRB 250202B: NuSTAR detection of the prompt emission
  74. GRB 250202C: GRBAlpha detection
  75. GRB 250202B: Fermi GBM Detection
  76. IceCube-250203A - IceCube observation of a high-energy neutrino candidate track-like event
  77. GRB 250129a: Liverpool Telescope optical follow-up
  78. GRB 250129A: 7DT Detection and Medium-band SED of Afterglow
  79. LIGO/Virgo/KAGRA S250202cu: Updated Sky localization
  80. GRB 250202C: Fermi GBM Final Real-time Localization
  81. LIGO/Virgo/KAGRA S250202cu: Identification of a GW compact binary merger candidate
  82. GRB 250129A: SVOM/C-GFT optical observations
  83. The EP-WXT trigger 01709131153 is not a real source
  84. LIGO/Virgo/KAGRA S250202ad: Retraction of GW compact binary merger candidate
  85. GRB 250202B: Fermi GBM Final Real-time Localization
  86. Swift GRB250129A: MASTER 4 days observations report
  87. GRB 250202A: Fermi GBM Final Real-time Localization
  88. Konus-Wind detection of GRB 250129A
  89. GRB 250129A: 1.3m DFOT Optical observations
  90. GRB 250201A: BALROG localization (Fermi Trigger 760096791 / GRB 250201417)
  91. GRB 250201A: Fermi GBM Final Real-time Localization
  92. LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations
  93. GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
  94. EP250108A / SN 2025kg: Upper limits from a neutrino search with IceCube
  95. GRB 250129A: iTelescope optical observation
  96. GRB 250129A: NOT optical observations of continuining activity
  97. GRB 250129A: GRANDMA/TAROT optical afterglow detection
  98. GRB 250128B: VLA radio upper limit
  99. Ep250125A: 1.3m DFOT optical upper limit
  100. GRB 250128B: Gemini-North optical extended source detection

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