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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"

24626 results found.

  1. EP250207b: Liverpool Telescope possible optical counterpart
  2. LIGO/Virgo/KAGRA S250211be: Identification of a GW compact binary merger candidate
  3. LIGO/Virgo/KAGRA S250211aa: Updated Sky localization and EM Bright Classification
  4. LIGO/Virgo/KAGRA S250211aa: Identification of a GW compact binary merger candidate
  5. GRB 250207A: Skynet optical afterglow observations
  6. GRB 241128A: VIRT Optical Upper Limit
  7. EP250207b: Gemini GMOS-N z-band observations
  8. EP250207A: Upper limits from Fermi-GBM Observations
  9. EP250207b: a new X-ray transient detected by Einstein Probe
  10. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  11. LIGO/Virgo/KAGRA S250206dm: Upper limits from GECAM Observations
  12. IceCube-250207A: Upper limits from a search for additional neutrino events in IceCube
  13. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  14. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  15. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  16. LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
  17. Fermi-LAT Gamma-ray Observations of IceCube-250207A
  18. GRB 250207A: 1.3m DFOT Optical observations
  19. LIGO/Virgo/KAGRA S250206dm: WFST follow-up observations
  20. GRB 250206A: Swift-XRT observations
  21. GRB 250129A: GRANDMA Continued Afterglow Detection
  22. GRB 250207A: Swift-BAT refined analysis
  23. LIGO/Virgo/KAGRA S250206dm: further Pan-STARRS observations and one candidate AT2025bbo
  24. LIGO/Virgo/KAGRA S250207bg: Updated NED Galaxies in the Localization Volume
  25. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  26. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  27. GRB 250205A: 1.3m DFOT optical upper limit
  28. LIGO/Virgo/KAGRA S250118az: Updated Sky localization
  29. LIGO/Virgo/KAGRA S250208ad: Updated Sky localization
  30. GRB 250206A: EIRSAT-1 GMOD Detection
  31. LIGO/Virgo/KAGRA S250206dm: (Update-7) NED Galaxies in the Localization Volume
  32. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
  33. GRB 250207B: Swift-XRT observations
  34. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  35. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates
  36. LIGO/Virgo/KAGRA S250208ad: Identification of a GW compact binary merger candidate
  37. LIGO/Virgo/KAGRA S250206dm: MMT galaxy targeted observations
  38. GRB 250207A: Swift-XRT refined Analysis
  39. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A & "Time Machine" Effect.
  40. EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
  41. GRB 250207A: Enhanced Swift-XRT position
  42. 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%
  43. GRB 250129A: ABObservatory SLOAN r’ afterglow detection
  44. GRB 250207A: REM IR afterglow detection
  45. LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap
  46. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS survey of the skymap for optical transients
  47. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits
  48. LIGO/Virgo/KAGRA S250207bg: NED Galaxies in the Localization Volume
  49. IGO/Virgo/KAGRA S250206dm: Virtual Telescope Project upper limit for the Neutrino IceCube Candidate
  50. GRB 250207A: REM optical afterglow detection
  51. LIGO/Virgo/KAGRA S250207bg: Identification of a GW compact binary merger candidate
  52. LIGO/Virgo/KAGRA S250206dm:GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  53. GRB 250207A: Swift/UVOT Detection
  54. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limit for the Neutrino IceCube Candidate
  55. LIGO/Virgo/KAGRA S250206dm: GOTO observations of optical candidates AT 2025azn and AT 2025azm
  56. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS observations of AT2025azm and AT2025azn
  57. LIGO/Virgo/KAGRA S250206dm: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  58. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the AT 2025azn Optical Candidate
  59. GRB 250129A: Continued AbAO and Mondy optical observations
  60. LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
  61. GRB 250207B: MAXI/GSC detection
  62. GRB 250207A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  63. LIGO/Virgo/KAGRA S250206dm: Updated-6 NED Galaxies in the Localization Volume
  64. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  65. LIGO/Virgo/KAGRA S250206dm: Upper limits from Fermi-GBM Observations
  66. GRB 250207A: Swift detection of a burst with optical counterpart
  67. Fermi-LAT Gamma-ray Observations of IceCube-250203A
  68. LIGO/Virgo/KAGRA S250206dm: Coverage and upper limits from MAXI/GSC observations
  69. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  70. LIGO/Virgo/KAGRA S250206dm: Updated NED Galaxies in the Localization Volume
  71. LIGO/Virgo/KAGRA S250206dm: Two counterpart neutrino candidates from IceCube neutrino searches
  72. LIGO/Virgo/KAGRA S250206dm: Identification of a GW compact binary merger candidate
  73. LIGO/Virgo/KAGRA S250206dm: NED Galaxies in the Localization Volume
  74. GRB 250206A: BALROG localization (Fermi Trigger 760564296 / GRB 250206827)
  75. GRB 250205A: Fermi GBM Observation
  76. GRB 250205A: REM NIR upper limit
  77. GRB 250205A: Swift/UVOT Upper Limits
  78. LIGO/Virgo/KAGRA S250205ee: Updated Sky localization and Source Classification
  79. EP250205a/GRB 250205A: Einstein Probe observation
  80. GRB 250127C: SVOM/GRM observation of a burst
  81. GRB 250204B: SVOM/GRM observation of a likely short burst
  82. GRB 250205A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  83. GRB 250205A: Swift/XRT detection
  84. GRB 250205A: Redshift from OSIRIS+/GTC z = 3.55
  85. GRB250205A: SVOM/VT optical afterglow detection
  86. GRB 250205A: OHP/T193 optical counterpart candidate
  87. LIGO/Virgo/KAGRA S250205ee: Identification of a GW compact binary merger candidate
  88. GRB 250205A: SVOM detection of a burst
  89. LIGO/Virgo/KAGRA S250205bk: NED Galaxies in the Localization Volume
  90. IPN triangulation of GRB 250201A
  91. LIGO/Virgo/KAGRA S250205bk: Updated Sky localization
  92. LIGO/Virgo/KAGRA S250205bk: Identification of a GW compact binary merger candidate
  93. GRB 250129A: Swift-BAT refined analysis
  94. EP 250108A: Upper limits from Fermi-GBM Observations
  95. IPN triangulation of GRB 250204B (short/hard)
  96. IPN triangulation of GRB 250202B
  97. LIGO/Virgo/KAGRA S250204ax: Updated Sky localization
  98. GRB 250204B: AstroSat CZTI detection of a short burst
  99. GRB 250129A: LCO late afterglow detection
  100. GRB 250129A: AbAO AS-32 and Mondy AZT-33IK optical observations

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