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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"

8476 results found.

  1. GRB 250205A: OHP/T193 optical counterpart candidate
  2. GRB 250205A: Liverpool Telescope optical counterpart candidate detection
  3. LIGO/Virgo/KAGRA S250205ee: Identification of a GW compact binary merger candidate
  4. LIGO/Virgo/KAGRA S250205bk: NED Galaxies in the Localization Volume
  5. LIGO/Virgo/KAGRA S250205bk: Updated Sky localization
  6. LIGO/Virgo/KAGRA S250205bk: Identification of a GW compact binary merger candidate
  7. EP 250108A: Upper limits from Fermi-GBM Observations
  8. LIGO/Virgo/KAGRA S250204ax: Updated Sky localization
  9. LIGO/Virgo/KAGRA S250204ax: Identification of a GW compact binary merger candidate
  10. IceCube-250203A - IceCube observation of a high-energy neutrino candidate track-like event
  11. LIGO/Virgo/KAGRA S250202cu: Updated Sky localization
  12. LIGO/Virgo/KAGRA S250202cu: Identification of a GW compact binary merger candidate
  13. LIGO/Virgo/KAGRA S250202ad: Retraction of GW compact binary merger candidate
  14. LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations
  15. EP250108A / SN 2025kg: Upper limits from a neutrino search with IceCube
  16. GRB 250129A: GRANDMA/TAROT optical afterglow detection
  17. GRB 250128B: Gemini-North optical extended source detection
  18. GRB 250128B: TNG optical upper limit
  19. Swift GRB 250129A: Global MASTER-Net Slowly evolving LC detection
  20. GRB 250129A: Swift detection of a burst with an optical counterpart
  21. GRB 250128B: GOTO optical upper limit
  22. EP250125a: Upper limits from Swift/BAT-GUANO
  23. GRB 250128B: Swift detection of a short burst
  24. GRB 250127A: Swift ToO observations
  25. EP250125A: Non-detection from Fermi-GBM Observations
  26. EP250125a: Optical upper limit with Kinder observations
  27. EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
  28. EP250108a/AT2025kg: 1.3m DFOT Optical observations
  29. LIGO/Virgo/KAGRA S250105bn: 1 counterpart neutrino candidate event from an IceCube neutrino search
  30. LIGO/Virgo/KAGRA S250119cv: Updated NED Galaxies in the Localization Volume
  31. LIGO/Virgo/KAGRA S250119cv: Updated Sky localization and EM Bright Classification
  32. LIGO/Virgo/KAGRA S250119cv: NED Galaxies in the Localization Volume
  33. LIGO/Virgo/KAGRA S250119cv: Identification of a GW compact binary merger candidate
  34. LIGO/Virgo/KAGRA S250119ag: Updated Sky localization
  35. LIGO/Virgo/KAGRA S250118dp: Updated Sky localization
  36. LIGO/Virgo/KAGRA S250119ag: Identification of a GW compact binary merger candidate
  37. LIGO/Virgo/KAGRA S250118dp: Identification of a GW compact binary merger candidate
  38. LIGO/Virgo/KAGRA S250118t: Updated Sky localization
  39. LIGO/Virgo/KAGRA S250118az: Identification of a GW compact binary merger candidate
  40. LIGO/Virgo/KAGRA S250118t: Identification of a GW compact binary merger candidate
  41. GRB 241217A / EP241217B: radio detection with the VLA
  42. LIGO/Virgo/KAGRA S250114ax: Updated NED Galaxies in the Localization Volume
  43. LIGO/Virgo/KAGRA S250114ax: Updated Sky localization
  44. GRB 250114B: Liverpool Telescope optical upper limit
  45. GRB 250114B : MITSuME Akeno optical afterglow candidate detection
  46. GRB 250114A: GRANDMA/TAROT optical afterglow detection
  47. GRB 250114B: Swift ToO observations
  48. LIGO/Virgo/KAGRA S250114ax: NED Galaxies in the Localization Volume
  49. LIGO/Virgo/KAGRA S250114ax: Identification of a GW compact binary merger candidate
  50. GRB 250114A: Swift detection of a burst with an optical counterpart
  51. EP250111a: Swift/XRT detection and fading
  52. EP250109a/GRB 250109A:SVOM/VT optical counterpart
  53. GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
  54. GRB 250108A: Swift/XRT afterglow fading
  55. LIGO/Virgo/KAGRA S250109bi: Updated Sky localization
  56. LIGO/Virgo/KAGRA S250109f: Updated Sky localization
  57. LIGO/Virgo/KAGRA S250108eo: Updated Sky localization
  58. GRB 250108B: REM optical/NIR upper limits
  59. EP250109a: SVOM/VT optical candidate
  60. EP250109a: Swift/XRT non-detection
  61. GRB 250108A: Swift/UVOT Upper Limits
  62. LIGO/Virgo/KAGRA S250109bi: Identification of a GW compact binary merger candidate
  63. GRB 250108A: NOT optical upper limit
  64. LIGO/Virgo/KAGRA S250109f: Identification of a GW compact binary merger candidate
  65. LIGO/Virgo/KAGRA S250108ha: Retraction of GW compact binary merger candidate
  66. GRB 250108B: Gemini-North Candidate Optical Afterglow Detection
  67. GRB 250103A: 1.6m Mephisto optical observations
  68. GRB 250108A:SVOM/VT optical candidate
  69. LIGO/Virgo/KAGRA S250108eo: Identification of a GW compact binary merger candidate
  70. GRB 250108B: Swift detection of a burst
  71. GRB 250108A: Swift ToO observations
  72. GRB 250107A: Swift ToO observations
  73. GRB 250106A: SVOM/VT 2nd optical deep observation
  74. GRB 250106A: NOT optical observations
  75. LIGO/Virgo/KAGRA S250104v: Updated Sky localization
  76. GRB 250106A: SVOM/VT optical candidate
  77. GRB 250106A: Swift ToO observations
  78. GRB 250103B: LCO/1m optical afterglow candidate detection
  79. GRB 250103A: Swift-XRT observations
  80. GRB 241228B: 1.3m DFOT Optical observations
  81. LIGO/Virgo/KAGRA S250104v: Identification of a GW compact binary merger candidate
  82. IceCube-250102A: Upper limits from a search for additional neutrino events in IceCube
  83. GRB 250103A: SVOM/VT optical counterpart confirmation
  84. GRB 250103A: Swift ToO observations
  85. IceCube-250101A: Upper limits from a search for additional neutrino events in IceCube
  86. GRB 250103B: Swift detection of a burst
  87. GRB 250103A: Xinglong 2.16m Optical Candidate
  88. GRB 250103A: GOTO optical upper limit
  89. GRB 250103A: SVOM detection of a long burst (duplicate submission)
  90. GRB 250103A: SVOM detection of a long burst
  91. LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO
  92. IceCube-250102A - IceCube observation of a high-energy neutrino candidate track-like event
  93. IceCube-250101A - IceCube observation of a high-energy neutrino candidate track-like event
  94. LIGO/Virgo/KAGRA S250101k: Updated Sky localization and Source Classification
  95. LIGO/Virgo/KAGRA S250101k: Upper limits from Fermi-GBM Observations
  96. GRB 250101A: Swift detection of a burst with an optical counterpart
  97. LIGO/Virgo/KAGRA S241231du: Coverage and upper limit from MAXI/GSC observations
  98. LIGO/Virgo/KAGRA S250101k: Identification of a GW compact binary merger candidate
  99. LIGO/Virgo/KAGRA S241231bg: Updated NED Galaxies in the Localization Volume
  100. LIGO/Virgo/KAGRA S241231bg: Updated Sky localization and EM Bright Classification

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