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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"

32537 results found.

  1. IceCube-250309A: Upper limits from Fermi-GBM Observations
  2. EP250308a: 1.6m Mephisto optical upper limits
  3. Konus-Wind detection of GRB 250309B
  4. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  5. IPN triangulation of GRB 250308A (short)
  6. IPN triangulation of GRB 250309B
  7. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  8. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  9. GRB 250309B: Swift-XRT refined Analysis
  10. GRB 250309B / IceCube-250309A: GECAM-B observations
  11. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  12. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  13. GRB 250309B / AT2025dws: SAO RAS optical observations
  14. GRB 250309B / AT2025dws: Swift-UVOT detection
  15. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  16. GRB 250309B: Fermi GBM Observation
  17. Fermi GRB 250309B: Global MASTER-Net observations report
  18. Fermi GRB 250309A: Global MASTER-Net observations report
  19. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  20. IceCube-250309A: No candidates from the Zwicky Transient Facility
  21. Fermi-LAT gamma-ray observations of IceCube-250309A
  22. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  23. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  24. GRB 230509B: Tiled Swift observations
  25. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  26. EP250308a: Global MASTER-Net observations report
  27. EP250308a: GSP optical upper limit
  28. GRB 250306A: EIRSAT-1 GMOD detection
  29. Fermi GRB 250307A: Global MASTER-Net observations report
  30. Konus-Wind detection of GRB 250306A
  31. GRB 250306A: Swift-BAT refined analysis
  32. GRB 250306A: NuSTAR detection of the prompt emission
  33. EP250304a: MeerKAT detection of a possible radio counterpart
  34. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  35. GRB 250305A: AstroSat CZTI detection
  36. EP250302a:Xinglong optical observations
  37. GRB 250306A: AstroSat CZTI detection
  38. Swift GRB 250306A: Global MASTER-Net observations report
  39. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  40. GRB250101A: Radio upper limits from VLA observations
  41. GRB 250305A: SVOM/GRM observation of a burst
  42. EP250304A: Upper limits from Fermi-GBM Observations
  43. Fermi GRB 250305A: Global MASTER-Net observations report
  44. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  45. EP250302a: Optical Observations at CrAO and SAO RAS
  46. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  47. EP 250304A: Optical counterpart detection by LCO
  48. EP250302A: 1.3m DFOT optical afterglow detection
  49. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  50. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  51. Konus-Wind detection of GRB 250222A
  52. EP250304a: REM NIR upper limits
  53. IPN triangulation of GRB 250222A
  54. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  55. EP250302a: Mondy Continued Optical Observations
  56. EP250304a: VLT/X-shooter redshift z = 0.200
  57. EP250304a: Swift-XRT detection of a fading X-ray source
  58. EP250304a: TRT optical counterpart detection
  59. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  60. EP250304a: Global MASTER-Net observations report
  61. EP250302a: SVOM/VT optical observation
  62. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  63. EP250302a: SAO RAS optical observations
  64. EP250302a : GIT optical follow-up
  65. EP250302a: VLT/X-shooter redshift confirmation
  66. EP250225a: the candidate optical counterpart is an AGN
  67. EP250302a: Kinder optical follow-up observations
  68. EP250302a: Swift/UVOT detection
  69. EP250302a: NUTTelA-TAO Early Measurments
  70. EP250302a: optical observation from the INAF Asiago Observatory
  71. EP250302a: REM NIR upper limits
  72. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  73. EP250302a: Mondy Observations and Optical Light Curve
  74. EP250302a: VLT/MUSE optical redshift z = 1.131
  75. INTEGRAL: end of scientific operations
  76. EP250302A: VLT near-infrared observations
  77. EP250302A: VLT/X-shooter tentative redshift
  78. EP250302a: OHP/T193 optical and spectroscopic observations
  79. EP250302a: Global MASTER-Net observations report
  80. EP250302a: Xinglong F60B optical observation
  81. EP250302a: Swift-XRT observations of a fading X-ray source
  82. EP250302a: Einstein Probe detection of an X-ray transient
  83. EP250302a: SVOM/C-GFT optical observations
  84. GRB 250226A: GRANDMA Optical Observations
  85. EP250302a: Montarrenti Observatory optical detection
  86. Fermi GRB 250302A: Global MASTER-Net observations report
  87. EP250302a: FTW optical and NIR detection
  88. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  89. GRB 250225B: VLT near-infrared afterglow confirmation
  90. EP250228a: Optical observations with Kinder and Swift/UVOT
  91. Konus-Wind detection of GRB 250226A
  92. GRB 250225B: EIRSAT-1 GMOD Detection
  93. GRB 250226A: KAO Optical Upper Limit
  94. GRB 250226A: AbAO AS-32 Optical Upper Limit
  95. EP250227a: Global MASTER-Net observations report
  96. EP250223A: Upper limits from Fermi-GBM Observations
  97. EP250227a: TRT optical upper limit
  98. GRB 250225B: VLT/HAWKI near-infrared observations
  99. EP250227a: Optical upper limits with Kinder observations
  100. EP250227a: NOT optical observations

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