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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"

7396 results found.

  1. GRB 250727A: EP-FXT counterpart detection
  2. GRB 250727A: Swift-XRT observations
  3. LIGO/Virgo/KAGRA S250727dc: Identification of a GW compact binary merger candidate
  4. LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
  5. LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
  6. LIGO/Virgo/KAGRA S250725l: Updated Sky localization
  7. LIGO/Virgo/KAGRA S250726ak: Updated Sky localization
  8. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  9. LIGO/Virgo/KAGRA S250725j: Updated Sky localization
  10. LIGO/Virgo/KAGRA S250725j: NED Galaxies in the 3-Initial Localization Volume
  11. GRB 250725A: SVOM/VT optical candidate
  12. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate (duplicate submission)
  13. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate
  14. LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
  15. GRB 250725A: Swift detection of a burst
  16. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  17. LIGO/Virgo/KAGRA S250711q: Updated Sky localization
  18. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  19. GRB 250721A: Tiled Swift observations
  20. LIGO/Virgo/KAGRA S250720j: Retraction of GW compact binary merger candidate
  21. GRB 250717B: COLIBRÍ optical upper limit
  22. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  23. GRB 250717B: Swift ToO observations
  24. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  25. GRB 250716A: Swift ToO observations
  26. GRB 250716A: GOTO tentative optical counterpart candidate
  27. GRB 250713A: SVOM/VT optical upper limit
  28. GRB 250713A: SVOM/C-GFT upper limit
  29. GRB 250713A: EP-FXT counterpart detection
  30. LIGO/Virgo/KAGRA S250712cd: Updated Sky localization
  31. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  32. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate (duplicate submission)
  33. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  34. EP250711a: NOT optical counterpart candidate
  35. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  36. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  37. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  38. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  39. IceCube-250708A: No Candidates from WINTER
  40. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  41. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  42. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  43. IceCube-250706A: No Candidates from WINTER
  44. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  45. IceCube-250708A - IceCube observation of a high-energy neutrino candidate track-like event
  46. LIGO/Virgo/KAGRA S250705cb: Updated Sky localization
  47. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  48. LIGO/Virgo/KAGRA S250702n: Updated Sky localization
  49. LIGO/Virgo/KAGRA S250701bq: Updated Sky localization
  50. LIGO/Virgo/KAGRA S250701bp: Updated Sky localization
  51. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  52. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  53. GRB250706B: Swift-XRT counterpart detection
  54. IceCube-250706A - IceCube observation of a high-energy neutrino candidate track-like event
  55. GRB 250706B: SVOM/VT optical observation
  56. GRB 250706A: Swift detection of a burst
  57. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  58. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  59. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  60. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  61. EP250704a / GRB250704B: Swift-XRT counterpart detection
  62. EP250704a / GRB 250704B - REM observations
  63. EP250704a: COLIBRÍ optical counterpart candidate
  64. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  65. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  66. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  67. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  68. GRB 250702F: Swift detection of a burst with an optical counterpart
  69. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  70. LIGO/Virgo/KAGRA S250701bq: Identification of a GW compact binary merger candidate
  71. LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
  72. GRB 250628B: Swift-XRT observations
  73. LIGO/Virgo/KAGRA S250629bs: Updated Sky localization
  74. LIGO/Virgo/KAGRA S250629ae: Updated Sky localization
  75. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  76. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate (duplicate submission)
  77. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  78. LIGO/Virgo/KAGRA S250628am: Updated Sky localization
  79. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  80. GRB 250628A: Swift detection of a burst
  81. GRB 250625A: Swift detection of a burst
  82. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  83. GRB 250617B: Swift detection of a burst with an optical counterpart
  84. EP#01709178975: Swift-XRT counterpart detection
  85. EP-WXT trigger 01709178975: GOTO optical upper limit
  86. GRB 250615A: Swift detection of a burst
  87. IceCube alert 141029_8144692 retraction
  88. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  89. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  90. sb25061218: Swift-XRT observations
  91. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  92. sb25061207: EP-FXT follow-up observation and afterglow candidate
  93. EP250612a: SVOM/VT optical candidate
  94. sb25061207: Swift-XRT observations
  95. sb25061207: SVOM/VT optical counterpart
  96. EP250610a: TNG NIR upper limit
  97. GRB 250610B: OHP/T120 optical counterpart candidate
  98. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  99. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  100. EP250610a: SVOM/VT optical upper limit

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