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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"

8474 results found.

  1. LIGO/Virgo/KAGRA S250205ee: Identification of a GW compact binary merger candidate
  2. LIGO/Virgo/KAGRA S250205bk: NED Galaxies in the Localization Volume
  3. LIGO/Virgo/KAGRA S250205bk: Updated Sky localization
  4. LIGO/Virgo/KAGRA S250205bk: Identification of a GW compact binary merger candidate
  5. EP 250108A: Upper limits from Fermi-GBM Observations
  6. LIGO/Virgo/KAGRA S250204ax: Updated Sky localization
  7. LIGO/Virgo/KAGRA S250204ax: Identification of a GW compact binary merger candidate
  8. IceCube-250203A - IceCube observation of a high-energy neutrino candidate track-like event
  9. LIGO/Virgo/KAGRA S250202cu: Updated Sky localization
  10. LIGO/Virgo/KAGRA S250202cu: Identification of a GW compact binary merger candidate
  11. LIGO/Virgo/KAGRA S250202ad: Retraction of GW compact binary merger candidate
  12. LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations
  13. EP250108A / SN 2025kg: Upper limits from a neutrino search with IceCube
  14. GRB 250129A: GRANDMA/TAROT optical afterglow detection
  15. GRB 250128B: Gemini-North optical extended source detection
  16. GRB 250128B: TNG optical upper limit
  17. Swift GRB 250129A: Global MASTER-Net Slowly evolving LC detection
  18. GRB 250129A: Swift detection of a burst with an optical counterpart
  19. GRB 250128B: GOTO optical upper limit
  20. EP250125a: Upper limits from Swift/BAT-GUANO
  21. GRB 250128B: Swift detection of a short burst
  22. GRB 250127A: Swift ToO observations
  23. EP250125A: Non-detection from Fermi-GBM Observations
  24. EP250125a: Optical upper limit with Kinder observations
  25. EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
  26. EP250108a/AT2025kg: 1.3m DFOT Optical observations
  27. LIGO/Virgo/KAGRA S250105bn: 1 counterpart neutrino candidate event from an IceCube neutrino search
  28. LIGO/Virgo/KAGRA S250119cv: Updated NED Galaxies in the Localization Volume
  29. LIGO/Virgo/KAGRA S250119cv: Updated Sky localization and EM Bright Classification
  30. LIGO/Virgo/KAGRA S250119cv: NED Galaxies in the Localization Volume
  31. LIGO/Virgo/KAGRA S250119cv: Identification of a GW compact binary merger candidate
  32. LIGO/Virgo/KAGRA S250119ag: Updated Sky localization
  33. LIGO/Virgo/KAGRA S250118dp: Updated Sky localization
  34. LIGO/Virgo/KAGRA S250119ag: Identification of a GW compact binary merger candidate
  35. LIGO/Virgo/KAGRA S250118dp: Identification of a GW compact binary merger candidate
  36. LIGO/Virgo/KAGRA S250118t: Updated Sky localization
  37. LIGO/Virgo/KAGRA S250118az: Identification of a GW compact binary merger candidate
  38. LIGO/Virgo/KAGRA S250118t: Identification of a GW compact binary merger candidate
  39. GRB 241217A / EP241217B: radio detection with the VLA
  40. LIGO/Virgo/KAGRA S250114ax: Updated NED Galaxies in the Localization Volume
  41. LIGO/Virgo/KAGRA S250114ax: Updated Sky localization
  42. GRB 250114B: Liverpool Telescope optical upper limit
  43. GRB 250114B : MITSuME Akeno optical afterglow candidate detection
  44. GRB 250114A: GRANDMA/TAROT optical afterglow detection
  45. GRB 250114B: Swift ToO observations
  46. LIGO/Virgo/KAGRA S250114ax: NED Galaxies in the Localization Volume
  47. LIGO/Virgo/KAGRA S250114ax: Identification of a GW compact binary merger candidate
  48. GRB 250114A: Swift detection of a burst with an optical counterpart
  49. EP250111a: Swift/XRT detection and fading
  50. EP250109a/GRB 250109A:SVOM/VT optical counterpart
  51. GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
  52. GRB 250108A: Swift/XRT afterglow fading
  53. LIGO/Virgo/KAGRA S250109bi: Updated Sky localization
  54. LIGO/Virgo/KAGRA S250109f: Updated Sky localization
  55. LIGO/Virgo/KAGRA S250108eo: Updated Sky localization
  56. GRB 250108B: REM optical/NIR upper limits
  57. EP250109a: SVOM/VT optical candidate
  58. EP250109a: Swift/XRT non-detection
  59. GRB 250108A: Swift/UVOT Upper Limits
  60. LIGO/Virgo/KAGRA S250109bi: Identification of a GW compact binary merger candidate
  61. GRB 250108A: NOT optical upper limit
  62. LIGO/Virgo/KAGRA S250109f: Identification of a GW compact binary merger candidate
  63. LIGO/Virgo/KAGRA S250108ha: Retraction of GW compact binary merger candidate
  64. GRB 250108B: Gemini-North Candidate Optical Afterglow Detection
  65. GRB 250103A: 1.6m Mephisto optical observations
  66. GRB 250108A:SVOM/VT optical candidate
  67. LIGO/Virgo/KAGRA S250108eo: Identification of a GW compact binary merger candidate
  68. GRB 250108B: Swift detection of a burst
  69. GRB 250108A: Swift ToO observations
  70. GRB 250107A: Swift ToO observations
  71. GRB 250106A: SVOM/VT 2nd optical deep observation
  72. GRB 250106A: NOT optical observations
  73. LIGO/Virgo/KAGRA S250104v: Updated Sky localization
  74. GRB 250106A: SVOM/VT optical candidate
  75. GRB 250106A: Swift ToO observations
  76. GRB 250103B: LCO/1m optical afterglow candidate detection
  77. GRB 250103A: Swift-XRT observations
  78. GRB 241228B: 1.3m DFOT Optical observations
  79. LIGO/Virgo/KAGRA S250104v: Identification of a GW compact binary merger candidate
  80. IceCube-250102A: Upper limits from a search for additional neutrino events in IceCube
  81. GRB 250103A: SVOM/VT optical counterpart confirmation
  82. GRB 250103A: Swift ToO observations
  83. IceCube-250101A: Upper limits from a search for additional neutrino events in IceCube
  84. GRB 250103B: Swift detection of a burst
  85. GRB 250103A: Xinglong 2.16m Optical Candidate
  86. GRB 250103A: GOTO optical upper limit
  87. GRB 250103A: SVOM detection of a long burst (duplicate submission)
  88. GRB 250103A: SVOM detection of a long burst
  89. LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO
  90. IceCube-250102A - IceCube observation of a high-energy neutrino candidate track-like event
  91. IceCube-250101A - IceCube observation of a high-energy neutrino candidate track-like event
  92. LIGO/Virgo/KAGRA S250101k: Updated Sky localization and Source Classification
  93. LIGO/Virgo/KAGRA S250101k: Upper limits from Fermi-GBM Observations
  94. GRB 250101A: Swift detection of a burst with an optical counterpart
  95. LIGO/Virgo/KAGRA S241231du: Coverage and upper limit from MAXI/GSC observations
  96. LIGO/Virgo/KAGRA S250101k: Identification of a GW compact binary merger candidate
  97. LIGO/Virgo/KAGRA S241231bg: Updated NED Galaxies in the Localization Volume
  98. LIGO/Virgo/KAGRA S241231bg: Updated Sky localization and EM Bright Classification
  99. LIGO/Virgo/KAGRA S241230ev: Updated Sky localization
  100. LIGO/Virgo/KAGRA S241231bg: NED Galaxies in the Localization Volume

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