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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"

7396 results found.

  1. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  2. LIGO/Virgo/KAGRA S250331o: Updated Sky localization
  3. GRB 250331D: Swift ToO observations
  4. LIGO/Virgo/KAGRA S250331o: NED Galaxies in the 3-Initial Localization Volume
  5. GRB 250328A: Swift-XRT refined Analysis
  6. GRB 250331C: Swift detection of a burst
  7. GRB 250331B: Swift detection of a burst
  8. LIGO/Virgo/KAGRA S250331o: Identification of a GW compact binary merger candidate
  9. GRB 250328A: 1.6m Mephisto optical observations
  10. IceCube-250330A - IceCube observation of a high-energy neutrino candidate track-like event
  11. GRB 250328A: A fading optical afterglow confirmed by SVOM/VT
  12. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  13. LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
  14. GRB 250329A: Swift-XRT afterglow detection
  15. GRB 250328A: SVOM/VT optical observation
  16. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  17. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  18. GRB 250329A: SVOM/VT optical counterpart confirmation
  19. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  20. LIGO/Virgo/KAGRA S250328ae: NED Galaxies in the 4-Update Localization Volume
  21. LIGO/Virgo/KAGRA S250328ae: Updated Sky localization
  22. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  23. GRB 250327B: 1.6m Mephisto optical observations
  24. GRB 250327B: SVOM/VT optically bright counterpart
  25. GRB 250327B: SAO RAS optical candidate
  26. GRB 250327A: SVOM/VT optical candidate
  27. LIGO/Virgo/KAGRA S250326y: Updated Sky localization
  28. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  29. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  30. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  31. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  32. GRB 250322A: Gemini-North redshift of candidate host galaxy
  33. GRB 250322A: VLT optical observations
  34. GRB 250322A: VLT near-infrared observations
  35. GRB 250322A: NOT optical upper limits
  36. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  37. GRB 250322A: Swift detection of a short burst
  38. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  39. GRB 250321B: Swift ToO observations
  40. GRB 250321B: SVOM detection of a sub-threshold transient event
  41. EP250321a: Kinder optical follow-up observations
  42. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  43. LIGO/Virgo/KAGRA S250319bu: Updated Sky localization
  44. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  45. GRB 250309B/AT2025dws: further ATCA observations
  46. GRB 250316A: AbAO AS-32 Optical Upper Limit
  47. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  48. GRB 250316A: Swift ToO observations
  49. GRB 250314A: EP-FXT afterglow detection
  50. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  51. EP250315a: optical counterpart candidate detected by Gemini North
  52. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  53. GRB 250314A: SVOM/VT upper limit
  54. GRB 250314A: NOT near-infrared candidate counterpart
  55. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  56. FRB 20250206A: Nondetection of Repeating Bursts from FRB 20250206A with FAST
  57. GRB 250313A: Swift ToO observations
  58. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  59. GRB 250312A: Swift detection of a burst
  60. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  61. GRB 250311A: Tiled Swift observations
  62. GRB 250309B: SVOM/VT optical observation
  63. GRB 250309B / AT2025dws: further SAO RAS optical observations
  64. IceCube-250309A: Upper limits from Fermi-GBM Observations
  65. Konus-Wind detection of GRB 250309B
  66. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  67. GRB 250309B / IceCube-250309A: GECAM-B observations
  68. GRB 250309B / AT2025dws: Swift-UVOT detection
  69. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  70. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  71. IceCube-250309A: No candidates from the Zwicky Transient Facility
  72. GRB 230509B: Tiled Swift observations
  73. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  74. The EP-WXT trigger 01709132387 is likely a flaring star
  75. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  76. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  77. LIGO/Virgo/KAGRA S250306ej: Retraction of GW compact binary merger candidate
  78. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  79. EP250225a: the candidate optical counterpart is an AGN
  80. EP250302a: Kinder optical follow-up observations
  81. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  82. EP250302a: Montarrenti Observatory optical detection
  83. IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
  84. GRB 250225B: VLT near-infrared afterglow confirmation
  85. EP250228a: Optical observations with Kinder and Swift/UVOT
  86. GRB 250225B: VLT/HAWKI near-infrared observations
  87. EP250227a: Optical upper limits with Kinder observations
  88. EP250225a: EP-FXT follow-up observation
  89. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  90. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  91. GRB 250225B: VLT/Xshooter imaging
  92. EP250225a: NOT optical candidate counterpart
  93. EP250226a/GRB 250226A: 1.6m Mephisto observations
  94. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  95. EP250226a/GRB 250226A: Kinder optical follow-up observations
  96. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  97. LIGO/Virgo/KAGRA S250227y: Retraction of GW compact binary merger candidate
  98. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  99. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  100. GRB 250225B: REM NIR upper limits

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