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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"

7407 results found.

  1. SVOM/sb25041603: SVOM detection of an X-ray transient
  2. EP250227a: Further NOT optical observations
  3. GRB 250407A: KAIT Optical Afterglow Candidate
  4. IceCube-250406A: No candidates from the Zwicky Transient Facility
  5. GRB 250407A: Swift ToO observations
  6. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  7. IceCube-250406A - IceCube observation of a high-energy neutrino candidate track-like event
  8. EP250402a: Optical upper limit with Kinder observations
  9. GRB 250402A: REM optical/NIR upper limits
  10. GRB 250402A: refined SVOM/MXT data analysis
  11. GRB 250219A: NOT candidate host galaxy detection
  12. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  13. LIGO/Virgo/KAGRA S250331o: Updated Sky localization
  14. GRB 250331D: Swift ToO observations
  15. LIGO/Virgo/KAGRA S250331o: NED Galaxies in the 3-Initial Localization Volume
  16. GRB 250328A: Swift-XRT refined Analysis
  17. GRB 250331C: Swift detection of a burst
  18. GRB 250331B: Swift detection of a burst
  19. LIGO/Virgo/KAGRA S250331o: Identification of a GW compact binary merger candidate
  20. GRB 250328A: 1.6m Mephisto optical observations
  21. IceCube-250330A - IceCube observation of a high-energy neutrino candidate track-like event
  22. GRB 250328A: A fading optical afterglow confirmed by SVOM/VT
  23. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  24. LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
  25. GRB 250329A: Swift-XRT afterglow detection
  26. GRB 250328A: SVOM/VT optical observation
  27. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  28. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  29. GRB 250329A: SVOM/VT optical counterpart confirmation
  30. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  31. LIGO/Virgo/KAGRA S250328ae: NED Galaxies in the 4-Update Localization Volume
  32. LIGO/Virgo/KAGRA S250328ae: Updated Sky localization
  33. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  34. GRB 250327B: 1.6m Mephisto optical observations
  35. GRB 250327B: SVOM/VT optically bright counterpart
  36. GRB 250327B: SAO RAS optical candidate
  37. GRB 250327A: SVOM/VT optical candidate
  38. LIGO/Virgo/KAGRA S250326y: Updated Sky localization
  39. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  40. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  41. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  42. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  43. GRB 250322A: Gemini-North redshift of candidate host galaxy
  44. GRB 250322A: VLT optical observations
  45. GRB 250322A: VLT near-infrared observations
  46. GRB 250322A: NOT optical upper limits
  47. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  48. GRB 250322A: Swift detection of a short burst
  49. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  50. GRB 250321B: Swift ToO observations
  51. GRB 250321B: SVOM detection of a sub-threshold transient event
  52. EP250321a: Kinder optical follow-up observations
  53. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  54. LIGO/Virgo/KAGRA S250319bu: Updated Sky localization
  55. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  56. GRB 250309B/AT2025dws: further ATCA observations
  57. GRB 250316A: AbAO AS-32 Optical Upper Limit
  58. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  59. GRB 250316A: Swift ToO observations
  60. GRB 250314A: EP-FXT afterglow detection
  61. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  62. EP250315a: optical counterpart candidate detected by Gemini North
  63. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  64. GRB 250314A: SVOM/VT upper limit
  65. GRB 250314A: NOT near-infrared candidate counterpart
  66. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  67. FRB 20250206A: Nondetection of Repeating Bursts from FRB 20250206A with FAST
  68. GRB 250313A: Swift ToO observations
  69. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  70. GRB 250312A: Swift detection of a burst
  71. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  72. GRB 250311A: Tiled Swift observations
  73. GRB 250309B: SVOM/VT optical observation
  74. GRB 250309B / AT2025dws: further SAO RAS optical observations
  75. IceCube-250309A: Upper limits from Fermi-GBM Observations
  76. Konus-Wind detection of GRB 250309B
  77. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  78. GRB 250309B / IceCube-250309A: GECAM-B observations
  79. GRB 250309B / AT2025dws: Swift-UVOT detection
  80. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  81. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  82. IceCube-250309A: No candidates from the Zwicky Transient Facility
  83. GRB 230509B: Tiled Swift observations
  84. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  85. The EP-WXT trigger 01709132387 is likely a flaring star
  86. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  87. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  88. LIGO/Virgo/KAGRA S250306ej: Retraction of GW compact binary merger candidate
  89. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  90. EP250225a: the candidate optical counterpart is an AGN
  91. EP250302a: Kinder optical follow-up observations
  92. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  93. EP250302a: Montarrenti Observatory optical detection
  94. IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
  95. GRB 250225B: VLT near-infrared afterglow confirmation
  96. EP250228a: Optical observations with Kinder and Swift/UVOT
  97. GRB 250225B: VLT/HAWKI near-infrared observations
  98. EP250227a: Optical upper limits with Kinder observations
  99. EP250225a: EP-FXT follow-up observation
  100. LIGO/Virgo/KAGRA S250227e: Updated Sky localization

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