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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"

32510 results found.

  1. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  2. GRB 250205A: 1.3m DFOT optical upper limit
  3. GRB 250206A: Tiled Swift observations
  4. LIGO/Virgo/KAGRA S250118az: Updated Sky localization
  5. LIGO/Virgo/KAGRA S250208ad: Updated Sky localization
  6. GRB 250206A: EIRSAT-1 GMOD Detection
  7. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
  8. GRB 250206A: Fermi-LAT detection
  9. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  10. IceCube-250203A: No transient candidates from the Zwicky Transient Facility
  11. LIGO/Virgo/KAGRA S250206dm: Spectroscopic Classification of AT2025bay and AT2025baz with Keck I/LRIS
  12. LIGO/Virgo/KAGRA S250206dm: Candidates from the Zwicky Transient Facility
  13. LIGO/Virgo/KAGRA S250206dm: ePESSTO+ classification of AT2025bar
  14. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates
  15. LIGO/Virgo/KAGRA S250208ad: Identification of a GW compact binary merger candidate
  16. LIGO/Virgo/KAGRA S250206dm: MMT galaxy targeted observations
  17. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A & "Time Machine" Effect.
  18. EP-WXT trigger 01709131361: correction to GCN 39214
  19. EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
  20. 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%
  21. LIGO/Virgo/KAGRA S250206dm: GOTO counterpart search update - AT2025bar
  22. EP-WXT trigger 01709131361 / LIGO/Virgo/KAGRA S250206dm: FTW optical and NIR observations
  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. GRB 250207A: FRAM-Auger optical detection
  28. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits
  29. GRB 250207B: Tiled Swift observations
  30. Konus-Wind detection of GRB 250204B
  31. IGO/Virgo/KAGRA S250206dm: Virtual Telescope Project upper limit for the Neutrino IceCube Candidate
  32. GRB 250207A: REM optical afterglow detection
  33. LIGO/Virgo/KAGRA S250207bg: Identification of a GW compact binary merger candidate
  34. LIGO/Virgo/KAGRA S250206dm:GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  35. GRB 250207A: Swift/UVOT Detection
  36. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limit for the Neutrino IceCube Candidate
  37. LIGO/Virgo/KAGRA S250206dm: GOTO observations of optical candidates AT 2025azn and AT 2025azm
  38. LIGO/Virgo/KAGRA S250206dm: SOAR galaxy targeted observations
  39. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS observations of AT2025azm and AT2025azn
  40. LIGO/Virgo/KAGRA S250206dm: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  41. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the AT 2025azn Optical Candidate
  42. GRB 250129A: Continued AbAO and Mondy optical observations
  43. LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
  44. GRB 250207A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  45. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  46. LIGO/Virgo/KAGRA S250206dm: Upper limits from Fermi-GBM Observations
  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: Identification of a GW compact binary merger candidate
  51. GRB 250205A: Fermi GBM Observation
  52. GRB 250205A: REM NIR upper limit
  53. EP250205a/GRB 250205A: FTW optical and NIR observations of the counterpart
  54. GRB 250205A: Swift/UVOT Upper Limits
  55. LIGO/Virgo/KAGRA S250205ee: Updated Sky localization and Source Classification
  56. EP250205a/GRB 250205A: correction to the source localization
  57. EP250205a/GRB 250205A: Einstein Probe observation
  58. GRB 250204B: SVOM/GRM observation of a likely short burst
  59. GRB 250205A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  60. GRB 250205A: Swift/XRT detection
  61. GRB 250205A: Redshift from OSIRIS+/GTC z = 3.55
  62. GRB250205A: SVOM/VT optical afterglow detection
  63. GRB 250205A: GOTO optical upper limits
  64. GRB 250205A: OHP/T193 optical counterpart candidate
  65. GRB 250205A: Liverpool Telescope optical counterpart candidate detection
  66. LIGO/Virgo/KAGRA S250205ee: Identification of a GW compact binary merger candidate
  67. Konus-Wind detection of GRB 250201A
  68. IPN triangulation of GRB 250201A
  69. LIGO/Virgo/KAGRA S250205bk: Updated Sky localization
  70. Konus-Wind detection of GRB 250202B
  71. LIGO/Virgo/KAGRA S250205bk: Identification of a GW compact binary merger candidate
  72. GRB 250129A: Swift-BAT refined analysis
  73. EP 250108A: Upper limits from Fermi-GBM Observations
  74. IPN triangulation of GRB 250204B (short/hard)
  75. IPN triangulation of GRB 250202B
  76. LIGO/Virgo/KAGRA S250204ax: Updated Sky localization
  77. GRB 250204B: AstroSat CZTI detection of a short burst
  78. GRB 250129A: LCO late afterglow detection
  79. GRB 250129A: AbAO AS-32 and Mondy AZT-33IK optical observations
  80. LIGO/Virgo/KAGRA S250204ax: Identification of a GW compact binary merger candidate
  81. GRB 250129A: COLIBRÍ/DDRAGO Afterglow Detection
  82. GRB 250202B: NuSTAR detection of the prompt emission
  83. GRB 250202C: GRBAlpha detection
  84. GRB 250129a: Liverpool Telescope optical follow-up
  85. GRB 240129A: further SAO RAS optical observations
  86. GRB 250129A: 7DT Detection and Medium-band SED of Afterglow
  87. LIGO/Virgo/KAGRA S250202cu: Updated Sky localization
  88. LIGO/Virgo/KAGRA S250202cu: Identification of a GW compact binary merger candidate
  89. GRB 250129A: SVOM/C-GFT optical observations
  90. GRB 250202B: AstroSat CZTI detection of a bright long GRB
  91. Swift GRB250129A: MASTER 4 days observations report
  92. GRB 250201A: INTEGRAL SPI/ACS detection
  93. Konus-Wind detection of GRB 250129A
  94. GRB 250129A: 1.3m DFOT Optical observations
  95. GRB 250129A: Liverpool Telescope observations suggest continued engine activity
  96. GRB 250129A: Skynet Continued Optical 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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