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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 S250818k: Coverage and upper limits from MAXI/GSC observations
  2. GRB 250818B: Swift-XRT afterglow detection
  3. GRB 250818B: GOTO optical counterpart candidate
  4. LIGO/Virgo/KAGRA S250818t: Identification of a GW compact binary merger candidate
  5. GRB 250818A: Swift detection of a burst
  6. sb25081602: Swift-XRT observations
  7. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  8. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  9. GRB 250814A: P200/WIRC observations of the afterglow candidate
  10. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  11. GRB 250814A: KAIT optical upper limit
  12. GRB 240814A: Fermi GBM Observation
  13. GRB 250814A: Possible afterglow candidate from P200/WIRC
  14. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  15. IceCube-250813A: Upper limits from a search for additional neutrino events in IceCube
  16. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  17. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  18. LIGO/Virgo/KAGRA S250813k: NED Galaxies in the 4-Update Localization Volume
  19. LIGO/Virgo/KAGRA S250813k: Updated Sky localization
  20. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  21. EP250812a: Liverpool Telescope upper limits
  22. IceCube-250813A - IceCube observation of a high-energy neutrino candidate track-like event
  23. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  24. GRB 250812A: Swift ToO observations
  25. EP 250812a: GOTO optical upper limit
  26. GRB 250812A: Kilonova-Catcher optical afterglow detection
  27. EP250812a: Swift-XRT counterpart detection
  28. IceCube-Cascade 250809A: Upper limits from a search for additional neutrino events in IceCube
  29. LIGO/Virgo/KAGRA S250810ck: Updated Sky localization and EM Bright Classification
  30. LIGO/Virgo/KAGRA S250810ck: Identification of a GW compact binary merger candidate
  31. GRB 250808A: VLT X-shooter candidate counterpart
  32. GRB 250809A: Swift detection of a gamma ray burst
  33. GRB 250808A: Swift-XRT candidate counterpart detection
  34. IceCube-250804A: Upper limits from a search for additional neutrino events in IceCube
  35. GRB 250806A: SVOM/MXT refined analysis
  36. GRB 250806A: SVOM/ECLAIRs refined analysis
  37. GRB 250806A: NOT z-band upper limit and host galaxy candidate
  38. EP 250807.979: GOTO optical upper limit
  39. EP250806a: Upper limit from Fermi-GBM Observations
  40. IceCube-Cascade 250804A: Upper limits from a search for additional neutrino events in IceCube
  41. GRB 250807B: Swift detection of a burst with an optical counterpart.
  42. GRB 250805A: Kilonova-Catcher optical upper limits
  43. EP250806a:SVOM/VT refined analysis
  44. EP250806a: Liverpool telescope optical upper limit
  45. GRB 250807A: Swift detection of a burst with an optical counterpart
  46. EP250806a: Earlier Detection of the VT Candidate by COLIBRÍ and LS
  47. EP250806a: SVOM /VT optical candidate
  48. GRB 250806A: KAIT optical upper limit
  49. GRB 250806A: SVOM/VT refined analysis
  50. IceCube-250804A - IceCube observation of a high-energy neutrino candidate track-like event
  51. GRB 250804B: Tiled Swift observations
  52. LIGO/Virgo/KAGRA S250802dn: Updated Sky localization
  53. LIGO/Virgo/KAGRA S250802dn: Identification of a GW compact binary merger candidate
  54. LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
  55. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS candidates
  56. LIGO/Virgo/KAGRA S250725j: GOTO pre-trigger detection of AT2025sib
  57. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  58. LIGO/Virgo/KAGRA S250725j: DECam DESGW Epoch 1-2 Candidates
  59. LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
  60. LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO
  61. LIGO/Virgo/KAGRA S250727dc: Upper limits from Swift/BAT-GUANO
  62. GRB 250727A: EP-FXT follow-up observation
  63. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  64. LIGO/Virgo/KAGRA S250727dc: Updated Sky localization
  65. GRB 250728A: Swift ToO observations
  66. LIGO/Virgo/KAGRA S250727cl: Updated Sky localization
  67. GRB 250727A: EP-FXT counterpart detection
  68. GRB 250727A: Swift-XRT observations
  69. LIGO/Virgo/KAGRA S250727dc: Identification of a GW compact binary merger candidate
  70. LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
  71. LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
  72. LIGO/Virgo/KAGRA S250725l: Updated Sky localization
  73. LIGO/Virgo/KAGRA S250726ak: Updated Sky localization
  74. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  75. LIGO/Virgo/KAGRA S250725j: Updated Sky localization
  76. LIGO/Virgo/KAGRA S250725j: NED Galaxies in the 3-Initial Localization Volume
  77. GRB 250725A: BOOTES-7 early optical detection
  78. GRB 250725A: SVOM/VT optical candidate
  79. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate (duplicate submission)
  80. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate
  81. LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
  82. GRB 250725A: Swift detection of a burst
  83. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  84. LIGO/Virgo/KAGRA S250711q: Updated Sky localization
  85. GRB 250721A: Tiled Swift observations
  86. LIGO/Virgo/KAGRA S250720j: Retraction of GW compact binary merger candidate
  87. GRB 250717B: COLIBRÍ optical upper limit
  88. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  89. GRB 250717B: Swift ToO observations
  90. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  91. GRB 250716A: Swift ToO observations
  92. GRB 250716A: GOTO tentative optical counterpart candidate
  93. GRB 250713A: SVOM/VT optical upper limit
  94. GRB 250713A: NOT optical upper limits
  95. GRB 250713A: SVOM/C-GFT upper limit
  96. GRB 250713A: EP-FXT counterpart detection
  97. LIGO/Virgo/KAGRA S250712cd: Updated Sky localization
  98. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  99. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate (duplicate submission)
  100. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate

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