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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

21829 results found.

  1. EP250806a: refined analysis of the EP-WXT and EP-FXT observations
  2. EP250806a: Earlier Detection of the VT Candidate by COLIBRÍ and LS
  3. GRB 250806A: J-band upper limit from WINTER
  4. GRB 250806A: KAIT optical upper limit
  5. GRB 250806A: Kilonova-Catcher optical upper limits
  6. GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  7. GRB 250805A: ESO/VLT observations
  8. GRB 250804B: Swift-XRT observations
  9. GRB 250805A: TRT optical upper limits
  10. GRB 250805A: Swift-XRT observations
  11. Swift GRB250805.26: Global MASTER-Net observations report
  12. GRB 250804B: Tiled Swift observations
  13. Fermi trigger No 776041355: Global MASTER-Net observations report
  14. EP250802a: Global MASTER-Net observations report
  15. EP250802a: Einstein Probe detection of an X-ray transient
  16. LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
  17. GRB 250702B: SMA observations
  18. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS candidates
  19. LIGO/Virgo/KAGRA S250725j: GOTO pre-trigger detection of AT2025sib
  20. EP250711a: CrAO and Assy optical observations
  21. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  22. EP250730a: Global MASTER-Net observations report
  23. EP250730a: Einstein Probe detection of an X-ray transient
  24. LIGO/Virgo/KAGRA S250725j: DECam DESGW Epoch 1-2 Candidates
  25. LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
  26. LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO
  27. LIGO/Virgo/KAGRA S250727dc: Upper limits from Swift/BAT-GUANO
  28. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  29. GRB 250725A: PRIME near-infrared observations
  30. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  31. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  32. GRB 250728A: Swift-XRT observations
  33. GRB 250727A: SVOM/ECLAIRs refined analysis
  34. EP-WXT trigger 01709195487: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  35. GRB 250728A: COLIBRÍ optical upper limit
  36. Fermi trigger No 775387550: Global MASTER-Net observations report
  37. GRB 250728A: Swift ToO observations
  38. GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
  39. GRB 250727A: AST3-2 Upper limit
  40. GRB250727A: SVOM/VT optical upper limit
  41. GRB 250727A: Swift-XRT observations
  42. LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
  43. LIGO/Virgo/KAGRA S250725j: NED Galaxies in the 3-Initial Localization Volume
  44. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  45. GRB 250725A: Swift/UVOT Upper Limits
  46. GRB 250725A: VLT/FORS2 spectroscopic redshift z = 5.26
  47. Fermi GRB 250725A: Global MASTER-Net observations report
  48. Swift GRB 250725A: Global MASTER-Net observations report
  49. EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
  50. EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz
  51. SVOM J195836+32283/sb25072103: Second VT observation
  52. SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
  53. SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
  54. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  55. GRB 250721A: Swift-XRT observations
  56. GRB 250713A : SVOM/ECLAIRs refined analysis
  57. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  58. GRB 250721A: Tiled Swift observations
  59. Fermi trigger No 774730635: Global MASTER-Net observations report
  60. EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
  61. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  62. GRB 250717B: Swift-XRT observations
  63. Swift GRB250718.01: Global MASTER-Net observations report
  64. GRB 250717B: Swift ToO observations
  65. GRB 270713A: Kitab and AbAO Optical Observations
  66. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  67. GRB 250716A: Swift-XRT afterglow detection
  68. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  69. GRB 250716A: Swift ToO observations
  70. GRB 250716A: GOTO tentative optical counterpart candidate
  71. Fermi GRB 250716A: Global MASTER-Net observations report
  72. Fermi GRB 250715A: Global MASTER-Net observations report
  73. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  74. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  75. GRB 250713A: Mephisto optical upper limits
  76. Fermi GRB 250714A: Global MASTER-Net observations report
  77. GRB 250713A: NOT optical upper limits
  78. GRB 250713A: OHP/T193 upper limit
  79. GRB 250713A: SVOM/C-GFT upper limit
  80. GRB 250706B/C: 7DT Follow-up Observations
  81. GRB 250713A: Swift-XRT observations
  82. EP250711a: COLIBRÍ continuous optical observations
  83. GRB 250713A: JinShan optical upper limits
  84. EP250711a: Global MASTER-Net observations report
  85. GRB 250711A: DDOTI Optical Upper Limit
  86. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  87. Fermi GRB 250711A: Global MASTER-Net observations report
  88. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  89. GRB 250704A: GRANDMA observations
  90. GRB 250704A: SVOM/ECLAIRs refined analysis
  91. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  92. GRB 250704B / EP250704a: 1.3 GHz MeerKAT Detection
  93. GRB 250702B,D,E / EP250702a: ALMA detection
  94. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  95. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  96. IceCube-250708A: No Candidates from WINTER
  97. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  98. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  99. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  100. EP/WXT 01709181970: GOTO observations confirm stellar variability

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