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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').
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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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submitter:"Judith Racusin"

23582 results found.

  1. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  2. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  3. GRB 250204B: GRBAlpha detection
  4. GRB 250204A: GRBAlpha detection
  5. LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
  6. Fermi-LAT Gamma-ray Observations of IceCube-250207A
  7. LIGO/Virgo/KAGRA S250206dm: WFST follow-up observations
  8. GRB 250206A: Swift-XRT observations
  9. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A BOOTES-5 and 2.2m CAHA optical upper limits
  10. GRB 250129A: GRANDMA Continued Afterglow Detection
  11. GRB 250207A: Swift-BAT refined analysis
  12. LIGO/Virgo/KAGRA S250206dm: further Pan-STARRS observations and one candidate AT2025bbo
  13. LIGO/Virgo/KAGRA S250207bg: Updated NED Galaxies in the Localization Volume
  14. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  15. GRB 250206A: EIRSAT-1 GMOD Detection
  16. LIGO/Virgo/KAGRA S250206dm: (Update-7) NED Galaxies in the Localization Volume
  17. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
  18. GRB 250207B: Swift-XRT observations
  19. LIGO/Virgo/KAGRA S250206dm: ePESSTO+ classification of AT2025bar
  20. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates
  21. EP250207a: EP-WXT detection and XRT follow-up observation
  22. LIGO/Virgo/KAGRA S250208ad: Identification of a GW compact binary merger candidate
  23. LIGO/Virgo/KAGRA S250206dm: MMT galaxy targeted observations
  24. GRB 250207A: Swift-XRT refined Analysis
  25. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A & "Time Machine" Effect.
  26. 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%
  27. LIGO/Virgo/KAGRA S250206dm: GOTO counterpart search update - AT2025bar
  28. GRB 250129A: ABObservatory SLOAN r’ afterglow detection
  29. GRB 250207A: REM IR afterglow detection
  30. LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap
  31. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS survey of the skymap for optical transients
  32. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits
  33. LIGO/Virgo/KAGRA S250207bg: NED Galaxies in the Localization Volume
  34. Konus-Wind detection of GRB 250204B
  35. GRB 250207A: REM optical afterglow detection
  36. LIGO/Virgo/KAGRA S250206dm:GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  37. GRB 250207A: Swift/UVOT Detection
  38. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limit for the Neutrino IceCube Candidate
  39. LIGO/Virgo/KAGRA S250206dm: GOTO observations of optical candidates AT 2025azn and AT 2025azm
  40. LIGO/Virgo/KAGRA S250206dm: SOAR galaxy targeted observations
  41. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS observations of AT2025azm and AT2025azn
  42. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the AT 2025azn Optical Candidate
  43. LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
  44. GRB 250207B: MAXI/GSC detection
  45. The EP-WXT trigger 01709131347 is likely a flaring star
  46. The EP-WXT trigger 01709131332 is likely a flaring star
  47. The EP-WXT trigger 01709131290 is likely a flaring star
  48. GRB 250207A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  49. LIGO/Virgo/KAGRA S250206dm: Updated-6 NED Galaxies in the Localization Volume
  50. GRB 250207A: Swift detection of a burst with optical counterpart
  51. Fermi-LAT Gamma-ray Observations of IceCube-250203A
  52. LIGO/Virgo/KAGRA S250206dm: Coverage and upper limits from MAXI/GSC observations
  53. LIGO/Virgo/KAGRA S250206dm: Updated NED Galaxies in the Localization Volume
  54. LIGO/Virgo/KAGRA S250206dm: Two counterpart neutrino candidates from IceCube neutrino searches
  55. LIGO/Virgo/KAGRA S250206dm: NED Galaxies in the Localization Volume
  56. GRB 250206A: Fermi GBM Final Real-time Localization
  57. GRB 250205A: REM NIR upper limit
  58. EP250205a/GRB 250205A: correction to the source localization
  59. EP250205a/GRB 250205A: Einstein Probe observation
  60. GRB 250205A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  61. GRB 250205A: Redshift from OSIRIS+/GTC z = 3.55
  62. GRB 250205A: GOTO optical upper limits
  63. LIGO/Virgo/KAGRA S250205ee: Identification of a GW compact binary merger candidate
  64. LIGO/Virgo/KAGRA S250205bk: NED Galaxies in the Localization Volume
  65. Konus-Wind detection of GRB 250201A
  66. IPN triangulation of GRB 250201A
  67. Konus-Wind detection of GRB 250202B
  68. LIGO/Virgo/KAGRA S250205bk: Identification of a GW compact binary merger candidate
  69. GRB 250129A: Swift-BAT refined analysis
  70. EP 250108A: Upper limits from Fermi-GBM Observations
  71. IPN triangulation of GRB 250204B (short/hard)
  72. IPN triangulation of GRB 250202B
  73. GRB 250204B: AstroSat CZTI detection of a short burst
  74. GRB 250129A: LCO late afterglow detection
  75. LIGO/Virgo/KAGRA S250204ax: Identification of a GW compact binary merger candidate
  76. GRB 250129A: COLIBRÍ/DDRAGO Afterglow Detection
  77. GRB 250202C: GRBAlpha detection
  78. GRB 240129A: further SAO RAS optical observations
  79. The EP-WXT trigger 01709131196 is likely a flaring star
  80. Konus-Wind detection of GRB 250129A
  81. LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations
  82. GRB 250129A: SAO RAS optical observations
  83. GRB 250129A: COLIBRÍ Continuing Detection of the Afterglow
  84. GRB 250129A: COLIBRÍ Optical Observations
  85. GRB 250128B: VLA possible radio detection
  86. GRB 250129A: continued KAIT observations indicating steep decay after 28.5h
  87. GRB 250129A: iTelescope optical observation
  88. GRB 250129A: NOT optical observations of continuining activity
  89. GRB 250129A: TNG NIR afterglow detection
  90. GRB 250129A: GRANDMA/TAROT optical afterglow detection
  91. GRB 250127A: EP-FXT second observation epoch and confirmation of the x-ray afterglow fading
  92. GRB 250128B: VLA radio upper limit
  93. GRB 250129A: Skynet optical observations
  94. GRB 250129A: KAIT optical observations of the rebrightening around 5.1 hours
  95. GRB 250129A: Swift-XRT refined Analysis
  96. The EP-WXT trigger 01709131085: KAIT confirmation of the stellar flare
  97. GRB 250128B: TNG optical upper limit
  98. GRB 250129A: Swift/UVOT Detection
  99. GRB 250128B: NOT optical upper limit
  100. GRB 250129A: REM optical/NIR afterglow detection

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