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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').
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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"
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submitter:"Judith Racusin"

28097 results found.

  1. EP250711a: CrAO and Assy optical observations
  2. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  3. EP250730a: COLIBRÍ optical upper limit
  4. GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
  5. LIGO/Virgo/KAGRA S250725j: DECam DESGW Epoch 1-2 Candidates
  6. LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
  7. LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO
  8. LIGO/Virgo/KAGRA S250727dc: Upper limits from Swift/BAT-GUANO
  9. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  10. GRB 250727A: EP-FXT follow-up observation
  11. GRB 250725A: PRIME near-infrared observations
  12. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  13. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  14. GRB 250728A: Swift-XRT observations
  15. GRB 250728A: COLIBRÍ optical upper limit
  16. LIGO/Virgo/KAGRA S250727dc: Updated Sky localization
  17. GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
  18. LIGO/Virgo/KAGRA S250727cl: Updated Sky localization
  19. GRB 250727A: EP-FXT counterpart detection
  20. GRB 250727A: Swift-XRT observations
  21. LIGO/Virgo/KAGRA S250727dc: Identification of a GW compact binary merger candidate
  22. LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
  23. LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
  24. LIGO/Virgo/KAGRA S250725l: Updated Sky localization
  25. LIGO/Virgo/KAGRA S250726ak: Updated Sky localization
  26. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  27. GRB 250725A: Swift-XRT refined Analysis
  28. GRB 250725A: Fermi GBM Observation
  29. LIGO/Virgo/KAGRA S250725j: Updated Sky localization
  30. GRB 250725A: Swift-BAT refined analysis
  31. LIGO/Virgo/KAGRA S250725j: NED Galaxies in the 3-Initial Localization Volume
  32. GRB 250725A: SVOM/GRM observation
  33. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  34. GRB 250725A: Swift/UVOT Upper Limits
  35. GRB 250725A: Fermi-LAT detection
  36. GRB 250725A: BOOTES-7 early optical detection
  37. GRB 250725A: SVOM/VT optical candidate
  38. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  39. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate
  40. LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
  41. GRB 250725A: Enhanced Swift-XRT position
  42. GRB 250725A: Swift detection of a burst
  43. Swift GRB 250725A: Global MASTER-Net OT detection
  44. EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
  45. SVOM J195836+32283 is not a real source
  46. EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz
  47. SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
  48. GRB 250721A: Fermi GBM Observation
  49. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  50. GRB 250721A: Swift-XRT observations
  51. GRB 250717B: SVOM/GRM observation
  52. LIGO/Virgo/KAGRA S250711q: Updated Sky localization
  53. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  54. GRB 250721A: MAXI/GSC detection
  55. LIGO/Virgo/KAGRA S250720j: Retraction of GW compact binary merger candidate
  56. GRB 250717B: COLIBRÍ optical upper limit
  57. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  58. GRB 250717B: Swift-XRT observations
  59. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  60. Swift GRB250718.01: Global MASTER-Net observations report
  61. GRB 270713A: Kitab and AbAO Optical Observations
  62. GRB 250717B: Fermi GBM Observation
  63. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  64. GRB 250716A: Swift-XRT afterglow detection
  65. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  66. GRB 250716A: Fermi GBM Observation
  67. GRB 250714A: SVOM/GRM observation
  68. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  69. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  70. GRB 250713A: Mephisto optical upper limits
  71. GRB 250713A: SVOM/VT optical upper limit
  72. GRB 250713A: NOT optical upper limits
  73. GRB 250713A: OHP/T193 upper limit
  74. GRB 250713A: SVOM/C-GFT upper limit
  75. GRB 250706B/C: 7DT Follow-up Observations
  76. GRB 250713A: Swift-XRT observations
  77. GRB 250713A: EP-FXT counterpart detection
  78. EP250711a: COLIBRÍ continuous optical observations
  79. GRB 250706A: Swift-BAT refined analysis
  80. GRB 250702F: Swift-BAT refined analysis
  81. GRB 250628A: Swift-BAT refined analysis
  82. LIGO/Virgo/KAGRA S250712cd: Updated Sky localization
  83. GRB 250713A: JinShan optical upper limits
  84. GRB 250713A: SVOM detection of a long burst
  85. EP250711a: Global MASTER-Net observations report
  86. GRB 250711A: DDOTI Optical Upper Limit
  87. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  88. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  89. GRB 250711A: SVOM/GRM observation
  90. EP250711a: NOT optical counterpart candidate
  91. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  92. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  93. GRB 250704A: GRANDMA observations
  94. GRB 250711A: BALROG localization (Fermi Trigger 773937617 / GRB 250711611)
  95. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  96. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  97. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  98. IceCube-250708A: No Candidates from WINTER
  99. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  100. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz

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