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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"

7417 results found.

  1. EP250302a: Kinder optical follow-up observations
  2. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  3. EP250302a: Montarrenti Observatory optical detection
  4. IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
  5. GRB 250225B: VLT near-infrared afterglow confirmation
  6. EP250228a: Optical observations with Kinder and Swift/UVOT
  7. GRB 250225B: VLT/HAWKI near-infrared observations
  8. EP250227a: Optical upper limits with Kinder observations
  9. EP250225a: EP-FXT follow-up observation
  10. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  11. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  12. GRB 250225B: VLT/Xshooter imaging
  13. EP250225a: NOT optical candidate counterpart
  14. EP250226a/GRB 250226A: 1.6m Mephisto observations
  15. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  16. EP250226a/GRB 250226A: Kinder optical follow-up observations
  17. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  18. LIGO/Virgo/KAGRA S250227y: Retraction of GW compact binary merger candidate
  19. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  20. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  21. GRB 250225B: REM NIR upper limits
  22. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  23. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  24. GRB 250225B: VLT optical and near-infrared candidate counterpart
  25. GRB 250225B: VLT/FORS2 candidate optical afterglow
  26. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  27. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  28. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  29. EP250223a: Kinder optical follow-up observations
  30. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  31. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  32. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  33. GRB 250219A: EP-FXT afterglow detection
  34. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  35. EP250223a: 1.6m Mephisto and 50cm array observations
  36. 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
  37. EP250223a: LCO detection of the afterglow
  38. EP250223a: NOT optical afterglow candidate
  39. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  40. GRB 250221A: 1.6m Mephisto optical detection
  41. LIGO/Virgo/KAGRA S250221gb: Retraction of GW compact binary merger candidate
  42. GRB 250221A: AKO Optical Upper Limit
  43. GRB 250221A: Swift/UVOT Detection
  44. LIGO/Virgo/KAGRA S250221eb: Retraction of GW compact binary merger candidate
  45. EP250220a: Liverpool Telescope optical upper limits
  46. EP250220a: Optical upper limit with Kinder observations
  47. GRB 250221A: Swift detection of a burst with an optical counterpart
  48. GRB 250219A: NOT optical observations
  49. GRB 250219A: 1.6m Mephisto optical upper limits
  50. GRB 250219A: Swift ToO observations
  51. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  52. GRB 250217C: Tiled Swift observations
  53. SVOM/sb25021804: SVOM detection of a long X-ray transient
  54. GRANDMA/OPD observations of GRB250215A
  55. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  56. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  57. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  58. GRB 250213A:SVOM/VT optical candidate
  59. GRB 250213A: Swift ToO observations
  60. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  61. EP250207B: Chandra localization of the X-ray counterpart
  62. LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
  63. EP250212a: Liverpool Telescope optical upper limits
  64. EP250207B: GTC z-band Observations
  65. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  66. EP250207b: NOT optical counterpart candidate
  67. GRB 250211A: Swift ToO observations
  68. LIGO/Virgo/KAGRA S250211be: Updated Sky localization
  69. IceCube-250207A: One candidate from the Zwicky Transient Facility
  70. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  71. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  72. Gemini-South spectroscopic redshift of EP250207b host galaxy candidate (z=0.082)
  73. LIGO/Virgo/KAGRA S250211be: Identification of a GW compact binary merger candidate
  74. LIGO/Virgo/KAGRA S250211aa: Updated Sky localization and EM Bright Classification
  75. LIGO/Virgo/KAGRA S250211aa: Identification of a GW compact binary merger candidate
  76. LIGO/Virgo/KAGRA S250206dm: Gemini-North spectroscopic observation of AT2025bbo and its host galaxy
  77. LIGO/Virgo/KAGRA S250206dm: Upper limits from GECAM Observations
  78. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  79. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  80. LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: MASTER observations and possible mother galaxy
  81. LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
  82. LIGO/Virgo/KAGRA S250206dm: WFST follow-up observations
  83. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A BOOTES-5 and 2.2m CAHA optical upper limits
  84. LIGO/Virgo/KAGRA S250206dm: further Pan-STARRS observations and one candidate AT2025bbo
  85. LIGO/Virgo/KAGRA S250207bg: Updated NED Galaxies in the Localization Volume
  86. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  87. GRB 250206A: Tiled Swift observations
  88. LIGO/Virgo/KAGRA S250118az: Updated Sky localization
  89. LIGO/Virgo/KAGRA S250208ad: Updated Sky localization
  90. LIGO/Virgo/KAGRA S250206dm: (Update-7) NED Galaxies in the Localization Volume
  91. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
  92. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  93. IceCube-250203A: No transient candidates from the Zwicky Transient Facility
  94. LIGO/Virgo/KAGRA S250206dm: ePESSTO+ classification of AT2025bar
  95. LIGO/Virgo/KAGRA S250208ad: Identification of a GW compact binary merger candidate
  96. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A & "Time Machine" Effect.
  97. 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%
  98. LIGO/Virgo/KAGRA S250206dm: GOTO counterpart search update - AT2025bar
  99. EP-WXT trigger 01709131361 / LIGO/Virgo/KAGRA S250206dm: FTW optical and NIR observations
  100. LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap

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