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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"

16155 results found.

  1. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  2. GRB 250812A: SVOM/VT optical afterglow confirmation
  3. GRB 250812A: TRT likely optical counterpart detection
  4. GRB 250812A: SVOM detection of a faint long burst
  5. GRB 250807B: SVOM/VT optical observation
  6. GRB 250809A: LCOGT Optical Upper Limits
  7. GRB 250808A: VLT X-shooter candidate counterpart
  8. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  9. GRB 250807A: SVOM/VT optical continued observation
  10. GRB 250808A: SVOM detection of a long burst
  11. GRB 250807B: Kilonova-Catcher optical afterglow detection
  12. GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
  13. EP250807a: NTT z-band optical upper limit
  14. GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
  15. GRB 250807A: SVOM/GRM observation
  16. GRB 250806A: NOT z-band upper limit and host galaxy candidate
  17. GRB 250807B: NTT optical observations
  18. EP250807a: EP-WXT detection of a fast X-ray transient
  19. EP 250807.979: GOTO optical upper limit
  20. EP250807a: COLIBRÍ optical upper limit
  21. GRB 250807A: SVOM/VT optical observation
  22. GRB 250807B: Swift detection of a burst with an optical counterpart.
  23. GRB 250805A: Kilonova-Catcher optical upper limits
  24. GRB 250805A: Swift/UVOT Upper Limits
  25. EP250806a: Liverpool telescope optical upper limit
  26. GRB 250807A: Swift detection of a burst with an optical counterpart
  27. EP250802a: EP-FXT follow-up observation
  28. EP250806a: Earlier Detection of the VT Candidate by COLIBRÍ and LS
  29. EP250806a: SVOM /VT optical candidate
  30. GRB 250806A: KAIT optical upper limit
  31. GRB 250806A: SVOM/VT refined analysis
  32. EP250806a: COLIBRÍ optical upper limit
  33. GRB 250806A: Kilonova-Catcher optical upper limits
  34. GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  35. GRB 250806A: SVOM/VT optical upper limit
  36. GRB 250805A: SVOM/VT optical counterpart
  37. GRB 250805A: ESO/VLT observations
  38. GRB 250805A: TRT optical upper limits
  39. GRB 250804B: SVOM/GRM observation of a short burst
  40. EP250730a: SVOM/VT optical upper limit
  41. EP250802a: Liverpool Telescope optical upper limits
  42. EP250802a: GROWTH-India Telescope optical upper limit
  43. LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
  44. LIGO/Virgo/KAGRA S250725j: GOTO pre-trigger detection of AT2025sib
  45. EP250711a: CrAO and Assy optical observations
  46. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  47. EP250730a: COLIBRÍ optical upper limit
  48. LIGO/Virgo/KAGRA S250725j: DECam DESGW Epoch 1-2 Candidates
  49. GRB 250725A: PRIME near-infrared observations
  50. GRB 250728A: COLIBRÍ optical upper limit
  51. GRB 250727A: AST3-2 Upper limit
  52. GRB250727A: SVOM/VT optical upper limit
  53. GRB 250725A: SVOM/GRM observation
  54. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  55. GRB 250725A: Swift/UVOT Upper Limits
  56. GRB 250725A: VLT/FORS2 spectroscopic redshift z = 5.26
  57. GRB 250725A: BOOTES-7 early optical detection
  58. GRB 250725A: SVOM/VT optical candidate
  59. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  60. Swift GRB 250725A: Global MASTER-Net OT detection
  61. SVOM J195836+32283/sb25072103: Second VT observation
  62. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  63. GRB 250717B: SVOM/GRM observation
  64. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  65. EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
  66. GRB 250717B: COLIBRÍ optical upper limit
  67. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  68. GRB 270713A: Kitab and AbAO Optical Observations
  69. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  70. GRB 250716A: GOTO tentative optical counterpart candidate
  71. GRB 250714A: SVOM/GRM observation
  72. GRB 250713A: Mephisto optical upper limits
  73. GRB 250713A: SVOM/VT optical upper limit
  74. GRB 250713A: NOT optical upper limits
  75. GRB 250706B/C: 7DT Follow-up Observations
  76. EP250711a: COLIBRÍ continuous optical observations
  77. GRB 250713A: JinShan optical upper limits
  78. GRB 250711A: DDOTI Optical Upper Limit
  79. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate (duplicate submission)
  80. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  81. GRB 250711A: SVOM/GRM observation
  82. EP250711a: NOT optical counterpart candidate
  83. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  84. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  85. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  86. EP/WXT 01709181970: GOTO observations confirm stellar variability
  87. EP250704a/GRB 250704B: 10 GHz VLA detection
  88. IceCube-250706A: No Candidates from WINTER
  89. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  90. GRB 250704B / EP250704a: VLA radio detection
  91. EP250704a/GRB250704B : HCT optical and NIR upper limits
  92. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  93. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  94. GRB 250702F: radio detection with the VLA
  95. GRB 250706B/C: VLT/X-shooter redshift z = 0.942
  96. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  97. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  98. GRB 250706B: Swift/UVOT Detection
  99. GRB 250702F: GRANDMA observations
  100. GRB 250706B: refined SVOM/MXT data analysis

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