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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"
body:"GRB"
submitter:"Judith Racusin"

24705 results found.

  1. GRB 250129A: GRANDMA Continued Afterglow Detection
  2. GRB 250207A: Swift-BAT refined analysis
  3. LIGO/Virgo/KAGRA S250206dm: further Pan-STARRS observations and one candidate AT2025bbo
  4. LIGO/Virgo/KAGRA S250207bg: Updated NED Galaxies in the Localization Volume
  5. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  6. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  7. GRB 250205A: 1.3m DFOT optical upper limit
  8. LIGO/Virgo/KAGRA S250118az: Updated Sky localization
  9. LIGO/Virgo/KAGRA S250208ad: Updated Sky localization
  10. GRB 250206A: EIRSAT-1 GMOD Detection
  11. LIGO/Virgo/KAGRA S250206dm: (Update-7) NED Galaxies in the Localization Volume
  12. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
  13. GRB 250207B: Swift-XRT observations
  14. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  15. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates
  16. LIGO/Virgo/KAGRA S250208ad: Identification of a GW compact binary merger candidate
  17. LIGO/Virgo/KAGRA S250206dm: MMT galaxy targeted observations
  18. GRB 250207A: Swift-XRT refined Analysis
  19. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A & "Time Machine" Effect.
  20. EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
  21. GRB 250207A: Enhanced Swift-XRT position
  22. 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%
  23. GRB 250129A: ABObservatory SLOAN r’ afterglow detection
  24. GRB 250207A: REM IR afterglow detection
  25. LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap
  26. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS survey of the skymap for optical transients
  27. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits
  28. LIGO/Virgo/KAGRA S250207bg: NED Galaxies in the Localization Volume
  29. IGO/Virgo/KAGRA S250206dm: Virtual Telescope Project upper limit for the Neutrino IceCube Candidate
  30. GRB 250207A: REM optical afterglow detection
  31. LIGO/Virgo/KAGRA S250207bg: Identification of a GW compact binary merger candidate
  32. LIGO/Virgo/KAGRA S250206dm:GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  33. GRB 250207A: Swift/UVOT Detection
  34. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limit for the Neutrino IceCube Candidate
  35. LIGO/Virgo/KAGRA S250206dm: GOTO observations of optical candidates AT 2025azn and AT 2025azm
  36. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS observations of AT2025azm and AT2025azn
  37. LIGO/Virgo/KAGRA S250206dm: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  38. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the AT 2025azn Optical Candidate
  39. GRB 250129A: Continued AbAO and Mondy optical observations
  40. LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
  41. GRB 250207B: MAXI/GSC detection
  42. GRB 250207A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  43. LIGO/Virgo/KAGRA S250206dm: Updated-6 NED Galaxies in the Localization Volume
  44. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  45. LIGO/Virgo/KAGRA S250206dm: Upper limits from Fermi-GBM Observations
  46. GRB 250207A: Swift detection of a burst with optical counterpart
  47. Fermi-LAT Gamma-ray Observations of IceCube-250203A
  48. LIGO/Virgo/KAGRA S250206dm: Coverage and upper limits from MAXI/GSC observations
  49. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  50. LIGO/Virgo/KAGRA S250206dm: Updated NED Galaxies in the Localization Volume
  51. LIGO/Virgo/KAGRA S250206dm: Two counterpart neutrino candidates from IceCube neutrino searches
  52. LIGO/Virgo/KAGRA S250206dm: Identification of a GW compact binary merger candidate
  53. LIGO/Virgo/KAGRA S250206dm: NED Galaxies in the Localization Volume
  54. GRB 250206A: BALROG localization (Fermi Trigger 760564296 / GRB 250206827)
  55. GRB 250205A: Fermi GBM Observation
  56. GRB 250205A: REM NIR upper limit
  57. GRB 250205A: Swift/UVOT Upper Limits
  58. LIGO/Virgo/KAGRA S250205ee: Updated Sky localization and Source Classification
  59. EP250205a/GRB 250205A: Einstein Probe observation
  60. GRB 250127C: SVOM/GRM observation of a burst
  61. GRB 250204B: SVOM/GRM observation of a likely short burst
  62. GRB 250205A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  63. GRB 250205A: Swift/XRT detection
  64. GRB 250205A: Redshift from OSIRIS+/GTC z = 3.55
  65. GRB250205A: SVOM/VT optical afterglow detection
  66. GRB 250205A: OHP/T193 optical counterpart candidate
  67. LIGO/Virgo/KAGRA S250205ee: Identification of a GW compact binary merger candidate
  68. GRB 250205A: SVOM detection of a burst
  69. LIGO/Virgo/KAGRA S250205bk: NED Galaxies in the Localization Volume
  70. IPN triangulation of GRB 250201A
  71. LIGO/Virgo/KAGRA S250205bk: Updated Sky localization
  72. LIGO/Virgo/KAGRA S250205bk: Identification of a GW compact binary merger candidate
  73. GRB 250129A: Swift-BAT refined analysis
  74. EP 250108A: Upper limits from Fermi-GBM Observations
  75. IPN triangulation of GRB 250204B (short/hard)
  76. IPN triangulation of GRB 250202B
  77. LIGO/Virgo/KAGRA S250204ax: Updated Sky localization
  78. GRB 250204B: AstroSat CZTI detection of a short burst
  79. GRB 250129A: LCO late afterglow detection
  80. GRB 250129A: AbAO AS-32 and Mondy AZT-33IK optical observations
  81. LIGO/Virgo/KAGRA S250204ax: Identification of a GW compact binary merger candidate
  82. GRB 250129A: COLIBRÍ/DDRAGO Afterglow Detection
  83. GRB 250202B: NuSTAR detection of the prompt emission
  84. GRB 250202B: Fermi GBM Detection
  85. GRB 250129a: Liverpool Telescope optical follow-up
  86. GRB 240129A: further SAO RAS optical observations
  87. GRB 250129A: 7DT Detection and Medium-band SED of Afterglow
  88. LIGO/Virgo/KAGRA S250202cu: Updated Sky localization
  89. LIGO/Virgo/KAGRA S250202cu: Identification of a GW compact binary merger candidate
  90. GRB 250129A: SVOM/C-GFT optical observations
  91. GRB 250202B: AstroSat CZTI detection of a bright long GRB
  92. Swift GRB250129A: MASTER 4 days observations report
  93. GRB 250129A: 1.3m DFOT Optical observations
  94. GRB 250201A: BALROG localization (Fermi Trigger 760096791 / GRB 250201417)
  95. GRB 250201A: Fermi GBM Final Real-time Localization
  96. LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations
  97. GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
  98. EP250108A / SN 2025kg: Upper limits from a neutrino search with IceCube
  99. GRB 250129A: SAO RAS optical observations
  100. GRB 250129A: COLIBRÍ Continuing Detection of the Afterglow

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