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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').
Advanced Search

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"

5833 results found.

  1. GRB 250329A: SVOM/VT optical counterpart confirmation
  2. GRB 250327B: LCO optical counterpart detection
  3. EP250321a: LCO optical counterpart detection
  4. EP250321a: Einstein Probe detection of an X-ray transient
  5. EP250226a/GRB 250226A: KAIT optical observations
  6. Fermi trigger No 763933627: Global MASTER-Net observations report
  7. Fermi GRB 250316A: Global MASTER-Net observations report
  8. GRB 250314A: Swift XRT Detection
  9. EP250315a: optical counterpart candidate detected by Gemini North
  10. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  11. Fermi GRB 250313A: Global MASTER-Net observations report
  12. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  13. GRB 250312A: Swift detection of a burst
  14. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  15. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  16. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  17. GRB 250309B / IceCube-250309A: GECAM-B observations
  18. GRB 250309B / AT2025dws: SAO RAS optical observations
  19. GRB 250309B / AT2025dws: Swift-UVOT detection
  20. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  21. GRB 250309B: Fermi GBM Observation
  22. Fermi GRB 250309B: Global MASTER-Net observations report
  23. Fermi GRB 250309A: Global MASTER-Net observations report
  24. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  25. IceCube-250309A: No candidates from the Zwicky Transient Facility
  26. Fermi-LAT gamma-ray observations of IceCube-250309A
  27. GRB 250309B: Fermi GBM Final Localization
  28. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  29. IceCube Alert 250309.32: Global MASTER-Net observations report
  30. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  31. EP250308a: Global MASTER-Net observations report
  32. Fermi GRB 250307A: Global MASTER-Net observations report
  33. Fermi trigger No 762963055: Global MASTER-Net observations report
  34. The EP-WXT trigger 01709132323 is likely a flaring star
  35. Fermi GRB 250305A: Global MASTER-Net observations report
  36. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  37. EP250302a: SAO RAS optical observations
  38. EP250302a: Nanshan/HMT optical counterpart detection
  39. GRB 250225B: VLT/HAWKI near-infrared observations
  40. EP250228a: updates on the EP observations
  41. EP250228a: Einstein Probe detection of an X-ray transient
  42. EP250225a: NOT optical candidate counterpart
  43. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  44. Fermi GRB 250225A: Global MASTER-Net observations report
  45. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  46. EP250223a: GOTO optical afterglow detections
  47. 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
  48. GRB 250221A: Assy optical observations
  49. EP250220a: EP-FXT follow-up observations
  50. Fermi Gamma-ray Burst Monitor trigger 761782146/250220923 is not a GRB
  51. GRB 250220A: Fermi GBM Final Real-time Localization
  52. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  53. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  54. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  55. Fermi GRB 250217C: Global MASTER-Net observations report
  56. Fermi GRB 250217A: Global MASTER-Net observations report
  57. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  58. EP250215a: Global MASTER-Net observations report
  59. LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
  60. EP250207b: NOT optical counterpart candidate
  61. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  62. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  63. EP250207b: Global MASTER-Net observations report
  64. LIGO/Virgo/KAGRA S250206dm: MASTER detection AT2025bbo
  65. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  66. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  67. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  68. IceCube Alert 250207.09: Global MASTER-Net observations report
  69. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  70. Fermi-LAT Gamma-ray Observations of IceCube-250207A
  71. GRB 250207A: Swift-BAT refined analysis
  72. LIGO/Virgo/KAGRA S250207bg: Updated NED Galaxies in the Localization Volume
  73. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  74. LIGO/Virgo/KAGRA S250206dm: (Update-7) NED Galaxies in the Localization Volume
  75. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates
  76. GRB 250207A: Enhanced Swift-XRT position
  77. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits
  78. LIGO/Virgo/KAGRA S250207bg: NED Galaxies in the Localization Volume
  79. GRB 250207A: Swift/UVOT Detection
  80. LIGO/Virgo/KAGRA S250206dm: SOAR galaxy targeted observations
  81. GRB 250207B: MAXI/GSC detection
  82. The EP-WXT trigger 01709131290 is likely a flaring star
  83. GRB 250207A: Swift detection of a burst with optical counterpart
  84. Fermi-LAT Gamma-ray Observations of IceCube-250203A
  85. LIGO/Virgo/KAGRA S250206dm: Identification of a GW compact binary merger candidate
  86. LIGO/Virgo/KAGRA S250205ee: Identification of a GW compact binary merger candidate
  87. LIGO/Virgo/KAGRA S250205bk: NED Galaxies in the Localization Volume
  88. Konus-Wind detection of GRB 250201A
  89. IPN triangulation of GRB 250201A
  90. Swift GRB250129A: MASTER 4 days observations report
  91. Konus-Wind detection of GRB 250129A
  92. GRB 250201A: BALROG localization (Fermi Trigger 760096791 / GRB 250201417)
  93. GRB 250201A: Fermi GBM Final Real-time Localization
  94. LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations
  95. GRB 250127A: EP-FXT second observation epoch and confirmation of the x-ray afterglow fading
  96. GRB 250129A: KAIT optical observations of the rebrightening around 5.1 hours
  97. The EP-WXT trigger 01709131085: KAIT confirmation of the stellar flare
  98. Swift GRB 250129A: Global MASTER-Net observations report
  99. Fermi GRB 250128B: Global MASTER-Net observations report
  100. GRB 250129A: Swift detection of a burst with an optical counterpart

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