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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"

2631 results found.

  1. IceCube-250706A - IceCube observation of a high-energy neutrino candidate track-like event
  2. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  3. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  4. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  5. GRB 250702F: Ondrejov D50 optical afterglow detection
  6. GRB 250628A: REM optical/NIR upper limits
  7. GRB 250625A: SAO RAS possible optical afterglow
  8. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  9. sb25061207: SVOM detection of a X-ray transient
  10. GRB 250610B: REM optical/NIR observations
  11. GRB 250610B: SVOM/VT optical shallow decay
  12. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  13. EP250610a: REM optical/NIR observations
  14. GRB 250608A: SVOM/GRM detection of a possible magnetar X-ray burst
  15. GRB 250605A: SVOM/VT optical upper limit
  16. GRB 250605A: LT optical observations
  17. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  18. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  19. GRB 250530C: Swift detection of a burst
  20. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  21. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
  22. GRB 250520A: REM optical/NIR early observations
  23. GRB 250515A/GOTO25cqo: SVOM/VT optical blue color
  24. GRB 250424A: COLIBRÍ detection of the associated supernova
  25. EP250512a/GRB 250512B: REM optical/NIR observations
  26. EP250511a: REM optical/NIR observations
  27. EP250511a: SVOM/VT optical candidate comfirmation
  28. EP250511a: COLIBRÍ optical counterpart candidate
  29. GRB 250510A: follow-up observation with EP-FXT
  30. GRB 250510A: SVOM possible detection of a burst
  31. EP250508a: REM optical/NIR observations
  32. GRB 250507A: REM optical/NIR observations
  33. IceCube-250506A - IceCube observation of a high-energy neutrino candidate track-like event
  34. GRB 250506A: REM optical/NIR upper limits
  35. GRB 250506A: Swift XRT observations and possible counterpart detection
  36. EP250428b: Pan-STARRS follow-up, upper limit on the optical counterpart, and possible host galaxy.
  37. IceCube-250429A - IceCube observation of a high-energy neutrino candidate track-like event
  38. EP250427a: Lesedi optical counterpart detection
  39. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  40. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event
  41. Fermi-LAT gamma-ray observations of IceCube-250421A
  42. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  43. IceCube-250421A - IceCube observation of a high-energy neutrino candidate track-like event
  44. EP250416a: Swift/XRT counterpart fading
  45. EP250416a: refined EP-WXT and EP-FXT analysis
  46. IceCube-250416A - IceCube observation of a high-energy neutrino candidate track-like event
  47. EP250227a: Further NOT optical observations
  48. IceCube-250406A - IceCube observation of a high-energy neutrino candidate track-like event
  49. GRB 250331C Swift-BAT refined analysis
  50. IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
  51. GRB 250322B possible detection by the AstroSat Satellite
  52. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  53. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  54. IceCube-250330A - IceCube observation of a high-energy neutrino candidate track-like event
  55. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  56. GRB 250329A: SVOM/VT optical counterpart confirmation
  57. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  58. GRB 250317B: NOT optical observations suggest an optical plateau phase
  59. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  60. SVOM/MXT upper limit on GRB 250314A
  61. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  62. EP trigger ID 01709061302: Lick/Kast spectroscopy with the 3 m Shane telescope
  63. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  64. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  65. GRB 250309B / AT2025dws: SAO RAS optical observations
  66. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  67. EP250304a: MeerKAT detection of a possible radio counterpart
  68. GRB250101A: Radio upper limits from VLA observations
  69. IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
  70. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  71. GRB 250221A: EP-FXT detection of the X-ray afterglow
  72. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  73. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  74. GRB 250221A: VLT/X-shooter redshift z = 0.768
  75. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  76. EP250212a: FTW optical and NIR upper limits
  77. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  78. GRB250101A: Radio upper limits from GMRT observations
  79. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  80. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  81. EP250207b: Liverpool Telescope possible optical counterpart
  82. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  83. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  84. LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: MASTER observations and possible mother galaxy
  85. LIGO/Virgo/KAGRA S250206dm: further Pan-STARRS observations and one candidate AT2025bbo
  86. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates
  87. EP250207a: EP-WXT detection and XRT follow-up observation
  88. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A & "Time Machine" Effect.
  89. EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
  90. LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap
  91. GRB 250207A: FRAM-Auger optical detection
  92. IceCube-250207A - IceCube observation of a high-energy neutrino candidate track-like event
  93. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the AT 2025azn Optical Candidate
  94. LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
  95. IceCube-250203A - IceCube observation of a high-energy neutrino candidate track-like event
  96. GRB 250128B: VLA possible radio detection
  97. GRB 250128B: VLT/HAWKI near-infrared observations
  98. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  99. ATCA detection of possible radio counterpart to GRB 250114A
  100. EP250108a: optical follow-up observations with the Liverpool Telescope

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