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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"

5819 results found.

  1. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  2. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  3. GRB 250309B / IceCube-250309A: GECAM-B observations
  4. GRB 250309B / AT2025dws: SAO RAS optical observations
  5. GRB 250309B / AT2025dws: Swift-UVOT detection
  6. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  7. GRB 250309B: Fermi GBM Observation
  8. Fermi GRB 250309B: Global MASTER-Net observations report
  9. Fermi GRB 250309A: Global MASTER-Net observations report
  10. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  11. IceCube-250309A: No candidates from the Zwicky Transient Facility
  12. Fermi-LAT gamma-ray observations of IceCube-250309A
  13. GRB 250309B: Fermi GBM Final Localization
  14. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  15. IceCube Alert 250309.32: Global MASTER-Net observations report
  16. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  17. EP250308a: Global MASTER-Net observations report
  18. Fermi GRB 250307A: Global MASTER-Net observations report
  19. Fermi trigger No 762963055: Global MASTER-Net observations report
  20. The EP-WXT trigger 01709132323 is likely a flaring star
  21. Fermi GRB 250305A: Global MASTER-Net observations report
  22. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  23. EP250302a: SAO RAS optical observations
  24. EP250302a: Nanshan/HMT optical counterpart detection
  25. GRB 250225B: VLT/HAWKI near-infrared observations
  26. EP250228a: updates on the EP observations
  27. EP250228a: Einstein Probe detection of an X-ray transient
  28. EP250225a: NOT optical candidate counterpart
  29. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  30. Fermi GRB 250225A: Global MASTER-Net observations report
  31. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  32. EP250223a: GOTO optical afterglow detections
  33. 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
  34. GRB 250221A: Assy optical observations
  35. EP250220a: EP-FXT follow-up observations
  36. Fermi Gamma-ray Burst Monitor trigger 761782146/250220923 is not a GRB
  37. GRB 250220A: Fermi GBM Final Real-time Localization
  38. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  39. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  40. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  41. Fermi GRB 250217C: Global MASTER-Net observations report
  42. Fermi GRB 250217A: Global MASTER-Net observations report
  43. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  44. EP250215a: Global MASTER-Net observations report
  45. LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
  46. EP250207b: NOT optical counterpart candidate
  47. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  48. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  49. EP250207b: Global MASTER-Net observations report
  50. LIGO/Virgo/KAGRA S250206dm: MASTER detection AT2025bbo
  51. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  52. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  53. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  54. IceCube Alert 250207.09: Global MASTER-Net observations report
  55. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  56. Fermi-LAT Gamma-ray Observations of IceCube-250207A
  57. GRB 250207A: Swift-BAT refined analysis
  58. LIGO/Virgo/KAGRA S250207bg: Updated NED Galaxies in the Localization Volume
  59. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  60. LIGO/Virgo/KAGRA S250206dm: (Update-7) NED Galaxies in the Localization Volume
  61. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates
  62. GRB 250207A: Enhanced Swift-XRT position
  63. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits
  64. LIGO/Virgo/KAGRA S250207bg: NED Galaxies in the Localization Volume
  65. GRB 250207A: Swift/UVOT Detection
  66. LIGO/Virgo/KAGRA S250206dm: SOAR galaxy targeted observations
  67. GRB 250207B: MAXI/GSC detection
  68. The EP-WXT trigger 01709131290 is likely a flaring star
  69. GRB 250207A: Swift detection of a burst with optical counterpart
  70. Fermi-LAT Gamma-ray Observations of IceCube-250203A
  71. LIGO/Virgo/KAGRA S250206dm: Identification of a GW compact binary merger candidate
  72. LIGO/Virgo/KAGRA S250205ee: Identification of a GW compact binary merger candidate
  73. LIGO/Virgo/KAGRA S250205bk: NED Galaxies in the Localization Volume
  74. Konus-Wind detection of GRB 250201A
  75. IPN triangulation of GRB 250201A
  76. Swift GRB250129A: MASTER 4 days observations report
  77. Konus-Wind detection of GRB 250129A
  78. GRB 250201A: BALROG localization (Fermi Trigger 760096791 / GRB 250201417)
  79. GRB 250201A: Fermi GBM Final Real-time Localization
  80. LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations
  81. GRB 250127A: EP-FXT second observation epoch and confirmation of the x-ray afterglow fading
  82. GRB 250129A: KAIT optical observations of the rebrightening around 5.1 hours
  83. The EP-WXT trigger 01709131085: KAIT confirmation of the stellar flare
  84. Swift GRB 250129A: Global MASTER-Net observations report
  85. Fermi GRB 250128B: Global MASTER-Net observations report
  86. GRB 250129A: Swift detection of a burst with an optical counterpart
  87. Swift GRB 250129A: Global MASTER-Net OT detection
  88. GRB 250127A: EP-FXT afterglow detection
  89. Fermi GRB 250127B: Global MASTER-Net observations report
  90. Fermi-LAT Gamma-ray Observations of IceCube-250101A
  91. IPN triangulation of GRB 250119B
  92. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  93. LIGO/Virgo/KAGRA S250118az: Identification of a GW compact binary merger candidate
  94. LIGO/Virgo/KAGRA S250114ax: Updated NED Galaxies in the Localization Volume
  95. Integral GRB250114.55: Global MASTER-Net observations report
  96. LIGO/Virgo/KAGRA S250114ax: NED Galaxies in the Localization Volume
  97. GRB 250114A: Swift detection of a burst with an optical counterpart
  98. GRB 250101A: Terskol Zeiss-2000 optical observations
  99. GRB 250109A / EP250109a: GRBAlpha detection
  100. GRB 250109A / EP250109a: Mephisto optical upper limits

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