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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"

7407 results found.

  1. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  2. GRB 250225B: VLT/Xshooter imaging
  3. EP250225a: NOT optical candidate counterpart
  4. EP250226a/GRB 250226A: 1.6m Mephisto observations
  5. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  6. EP250226a/GRB 250226A: Kinder optical follow-up observations
  7. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  8. LIGO/Virgo/KAGRA S250227y: Retraction of GW compact binary merger candidate
  9. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  10. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  11. GRB 250225B: REM NIR upper limits
  12. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  13. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  14. GRB 250225B: VLT optical and near-infrared candidate counterpart
  15. GRB 250225B: VLT/FORS2 candidate optical afterglow
  16. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  17. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  18. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  19. EP250223a: Kinder optical follow-up observations
  20. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  21. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  22. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  23. GRB 250219A: EP-FXT afterglow detection
  24. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  25. EP250223a: 1.6m Mephisto and 50cm array observations
  26. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO trigger with ID 762004910: Identification of a GW compact binary merger candidate possibly associated with a sub-threshold Swift/BAT-GUANO trigger
  27. EP250223a: LCO detection of the afterglow
  28. EP250223a: NOT optical afterglow candidate
  29. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  30. GRB 250221A: 1.6m Mephisto optical detection
  31. LIGO/Virgo/KAGRA S250221gb: Retraction of GW compact binary merger candidate
  32. GRB 250221A: AKO Optical Upper Limit
  33. GRB 250221A: Swift/UVOT Detection
  34. LIGO/Virgo/KAGRA S250221eb: Retraction of GW compact binary merger candidate
  35. EP250220a: Liverpool Telescope optical upper limits
  36. EP250220a: Optical upper limit with Kinder observations
  37. GRB 250221A: Swift detection of a burst with an optical counterpart
  38. GRB 250219A: NOT optical observations
  39. GRB 250219A: 1.6m Mephisto optical upper limits
  40. GRB 250219A: Swift ToO observations
  41. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  42. GRB 250217C: Tiled Swift observations
  43. SVOM/sb25021804: SVOM detection of a long X-ray transient
  44. GRANDMA/OPD observations of GRB250215A
  45. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  46. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  47. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  48. GRB 250213A:SVOM/VT optical candidate
  49. GRB 250213A: Swift ToO observations
  50. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  51. EP250207B: Chandra localization of the X-ray counterpart
  52. LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
  53. EP250212a: Liverpool Telescope optical upper limits
  54. EP250207B: GTC z-band Observations
  55. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  56. EP250207b: NOT optical counterpart candidate
  57. GRB 250211A: Swift ToO observations
  58. LIGO/Virgo/KAGRA S250211be: Updated Sky localization
  59. IceCube-250207A: One candidate from the Zwicky Transient Facility
  60. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  61. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  62. Gemini-South spectroscopic redshift of EP250207b host galaxy candidate (z=0.082)
  63. LIGO/Virgo/KAGRA S250211be: Identification of a GW compact binary merger candidate
  64. LIGO/Virgo/KAGRA S250211aa: Updated Sky localization and EM Bright Classification
  65. LIGO/Virgo/KAGRA S250211aa: Identification of a GW compact binary merger candidate
  66. LIGO/Virgo/KAGRA S250206dm: Gemini-North spectroscopic observation of AT2025bbo and its host galaxy
  67. LIGO/Virgo/KAGRA S250206dm: Upper limits from GECAM Observations
  68. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  69. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  70. LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: MASTER observations and possible mother galaxy
  71. LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
  72. LIGO/Virgo/KAGRA S250206dm: WFST follow-up observations
  73. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A BOOTES-5 and 2.2m CAHA optical upper limits
  74. LIGO/Virgo/KAGRA S250206dm: further Pan-STARRS observations and one candidate AT2025bbo
  75. LIGO/Virgo/KAGRA S250207bg: Updated NED Galaxies in the Localization Volume
  76. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  77. GRB 250206A: Tiled Swift observations
  78. LIGO/Virgo/KAGRA S250118az: Updated Sky localization
  79. LIGO/Virgo/KAGRA S250208ad: Updated Sky localization
  80. LIGO/Virgo/KAGRA S250206dm: (Update-7) NED Galaxies in the Localization Volume
  81. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
  82. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  83. IceCube-250203A: No transient candidates from the Zwicky Transient Facility
  84. LIGO/Virgo/KAGRA S250206dm: ePESSTO+ classification of AT2025bar
  85. LIGO/Virgo/KAGRA S250208ad: Identification of a GW compact binary merger candidate
  86. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A & "Time Machine" Effect.
  87. 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%
  88. LIGO/Virgo/KAGRA S250206dm: GOTO counterpart search update - AT2025bar
  89. EP-WXT trigger 01709131361 / LIGO/Virgo/KAGRA S250206dm: FTW optical and NIR observations
  90. LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap
  91. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS survey of the skymap for optical transients
  92. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits
  93. GRB 250207B: Tiled Swift observations
  94. LIGO/Virgo/KAGRA S250207bg: NED Galaxies in the Localization Volume
  95. IGO/Virgo/KAGRA S250206dm: Virtual Telescope Project upper limit for the Neutrino IceCube Candidate
  96. IceCube-250207A - IceCube observation of a high-energy neutrino candidate track-like event
  97. LIGO/Virgo/KAGRA S250207bg: Identification of a GW compact binary merger candidate
  98. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limit for the Neutrino IceCube Candidate
  99. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS observations of AT2025azm and AT2025azn
  100. LIGO/Virgo/KAGRA S250206dm: No counterpart candidates in INTEGRAL SPI-ACS prompt observation

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