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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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submitter:"Judith Racusin"

21953 results found.

  1. EP250207b: Global MASTER-Net observations report
  2. Gemini-South spectroscopic redshift of EP250207b host galaxy candidate (z=0.082)
  3. GRB 250207A: Skynet optical afterglow observations
  4. LIGO/VIRGO/KAGRA S250206dm: AT 2025bbo spectroscopic observations with NIRES on Keck II
  5. LIGO/Virgo/KAGRA S250206dm: Gemini-North spectroscopic observation of AT2025bbo and its host galaxy
  6. EP250207b: Gemini GMOS-N z-band observations
  7. EP250207A: Upper limits from Fermi-GBM Observations
  8. GRB 250210A: INTEGRAL SPI-ACS detection
  9. EP250207b: a new X-ray transient detected by Einstein Probe
  10. Fermi GRB 250210A: Global MASTER-Net observations report
  11. LIGO/Virgo/KAGRA S250206dm: Upper limits from GECAM Observations
  12. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  13. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  14. IceCube Alert 250207.09: Global MASTER-Net observations report
  15. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  16. LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: MASTER observations and possible mother galaxy
  17. LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
  18. Fermi-LAT Gamma-ray Observations of IceCube-250207A
  19. GRB 250207A: 1.3m DFOT Optical observations
  20. LIGO/Virgo/KAGRA S250206dm: WFST follow-up observations
  21. GRB 250206A: Swift-XRT observations
  22. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A BOOTES-5 and 2.2m CAHA optical upper limits
  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 S250206dm: GECKO Observation with 7DT and KMTNet
  26. GRB 250205A: 1.3m DFOT optical upper limit
  27. GRB 250206A: Tiled Swift observations
  28. LIGO/Virgo/KAGRA S250206dm: (Update-7) NED Galaxies in the Localization Volume
  29. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
  30. GRB 250207B: Swift-XRT observations
  31. IceCube-250203A: No transient candidates from the Zwicky Transient Facility
  32. LIGO/Virgo/KAGRA S250206dm: Spectroscopic Classification of AT2025bay and AT2025baz with Keck I/LRIS
  33. LIGO/Virgo/KAGRA S250206dm: Candidates from the Zwicky Transient Facility
  34. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates
  35. LIGO/Virgo/KAGRA S250206dm: MMT galaxy targeted observations
  36. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A & "Time Machine" Effect.
  37. EP-WXT trigger 01709131361: correction to GCN 39214
  38. EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
  39. 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%
  40. LIGO/Virgo/KAGRA S250206dm: GOTO counterpart search update - AT2025bar
  41. EP-WXT trigger 01709131361 / LIGO/Virgo/KAGRA S250206dm: FTW optical and NIR observations
  42. GRB 250129A: ABObservatory SLOAN r’ afterglow detection
  43. GRB 250207A: REM IR afterglow detection
  44. LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap
  45. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS survey of the skymap for optical transients
  46. GRB 250207A: FRAM-Auger optical detection
  47. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits
  48. GRB 250207B: Tiled Swift observations
  49. LIGO/Virgo/KAGRA S250207bg: NED Galaxies in the Localization Volume
  50. GRB 250207A: REM optical afterglow detection
  51. LIGO/Virgo/KAGRA S250206dm:GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  52. GRB 250207A: Swift/UVOT Detection
  53. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limit for the Neutrino IceCube Candidate
  54. LIGO/Virgo/KAGRA S250206dm: GOTO observations of optical candidates AT 2025azn and AT 2025azm
  55. LIGO/Virgo/KAGRA S250206dm: SOAR galaxy targeted observations
  56. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS observations of AT2025azm and AT2025azn
  57. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the AT 2025azn Optical Candidate
  58. GRB 250129A: Continued AbAO and Mondy optical observations
  59. LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
  60. GRB 250207A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  61. LIGO/Virgo/KAGRA S250206dm: Updated-6 NED Galaxies in the Localization Volume
  62. LIGO/Virgo/KAGRA S250206dm: Upper limits from Fermi-GBM Observations
  63. Fermi-LAT Gamma-ray Observations of IceCube-250203A
  64. LIGO/Virgo/KAGRA S250206dm: Coverage and upper limits from MAXI/GSC observations
  65. LIGO/Virgo/KAGRA S250206dm: Updated NED Galaxies in the Localization Volume
  66. LIGO/Virgo/KAGRA S250206dm: Two counterpart neutrino candidates from IceCube neutrino searches
  67. LIGO/Virgo/KAGRA S250206dm: NED Galaxies in the Localization Volume
  68. GRB 250205A: REM NIR upper limit
  69. EP250205a/GRB 250205A: FTW optical and NIR observations of the counterpart
  70. GRB 250205A: Swift/UVOT Upper Limits
  71. GRB 250205A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  72. GRB 250205A: Swift/XRT detection
  73. GRB 250205A: GOTO optical upper limits
  74. GRB 250205A: OHP/T193 optical counterpart candidate
  75. GRB 250205A: Liverpool Telescope optical counterpart candidate detection
  76. LIGO/Virgo/KAGRA S250205bk: NED Galaxies in the Localization Volume
  77. EP 250108A: Upper limits from Fermi-GBM Observations
  78. GRB 250129A: LCO late afterglow detection
  79. GRB 250129A: AbAO AS-32 and Mondy AZT-33IK optical observations
  80. GRB 250129A: COLIBRÍ/DDRAGO Afterglow Detection
  81. GRB 250129a: Liverpool Telescope optical follow-up
  82. GRB 240129A: further SAO RAS optical observations
  83. GRB 250129A: 7DT Detection and Medium-band SED of Afterglow
  84. GRB 250129A: SVOM/C-GFT optical observations
  85. Swift GRB250129A: MASTER 4 days observations report
  86. GRB 250201A: INTEGRAL SPI/ACS detection
  87. GRB 250129A: 1.3m DFOT Optical observations
  88. GRB 250129A: Liverpool Telescope observations suggest continued engine activity
  89. LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations
  90. GRB 250129A: Skynet Continued Optical Observations
  91. GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
  92. GRB 250129A: SAO RAS optical observations
  93. GRB 250129A: COLIBRÍ Continuing Detection of the Afterglow
  94. GRB 250129A: optical photometry from Konkoly
  95. GRB 250129A: COLIBRÍ Optical Observations
  96. GRB 250128B: VLA possible radio detection
  97. GRB 250129A: continued KAIT observations indicating steep decay after 28.5h
  98. GRB 250129A: NOT optical observations of continuining activity
  99. GRB 250129a: Liverpool Telescope optical follow-up
  100. GRB 250129A: GRANDMA/TAROT optical afterglow detection

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