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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').
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"

21769 results found.

  1. GRB 250806A: SVOM/VT optical upper limit
  2. GRB 250806A: SVOM detection of a soft burst
  3. GRB 250805A: SVOM/VT optical counterpart
  4. GRB 250804B: Swift-XRT observations
  5. GRB 250805A: Enhanced Swift-XRT position
  6. GRB 250805A: TRT optical upper limits
  7. GRB 250805A: Swift-XRT observations
  8. GRB 250804B: SVOM/GRM observation of a short burst
  9. EP250802a: additional Liverpool Telescope upper limits
  10. EP250730a: SVOM/VT optical upper limit
  11. EP250802a: Liverpool Telescope optical upper limits
  12. EP250802a: GROWTH-India Telescope optical upper limit
  13. LIGO/Virgo/KAGRA S250802dn: Identification of a GW compact binary merger candidate
  14. LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
  15. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS candidates
  16. LIGO/Virgo/KAGRA S250725j: GOTO pre-trigger detection of AT2025sib
  17. EP250711a: CrAO and Assy optical observations
  18. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  19. EP250730a: COLIBRÍ optical upper limit
  20. GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
  21. LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
  22. LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO
  23. LIGO/Virgo/KAGRA S250727dc: Upper limits from Swift/BAT-GUANO
  24. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  25. GRB 250725A: PRIME near-infrared observations
  26. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  27. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  28. GRB 250727A: SVOM/ECLAIRs refined analysis
  29. GRB 250728A: COLIBRÍ optical upper limit
  30. LIGO/Virgo/KAGRA S250727dc: Identification of a GW compact binary merger candidate
  31. LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
  32. LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
  33. GRB 250727A: SVOM detection of a burst
  34. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  35. Konus-Wind detection of GRB 250725A
  36. GRB 250725A: SVOM/GRM observation
  37. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  38. GRB 250725A: Swift/UVOT Upper Limits
  39. GRB 250725A: Fermi-LAT detection
  40. GRB 250725A: SVOM/VT optical candidate
  41. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  42. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate
  43. LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
  44. GRB 250725A: Enhanced Swift-XRT position
  45. GRB 250725A: Swift detection of a burst
  46. Swift GRB 250725A: Global MASTER-Net OT detection
  47. EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
  48. SVOM J195836+32283 is not a real source
  49. EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz
  50. SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
  51. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  52. GRB 250721A: Swift-XRT observations
  53. GRB 250717B: SVOM/GRM observation
  54. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  55. EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
  56. GRB 250717B: COLIBRÍ optical upper limit
  57. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  58. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  59. GRB 270713A: Kitab and AbAO Optical Observations
  60. GRB 250717B: Fermi GBM Observation
  61. Konus-Wind detection of GRB 250716A
  62. GRB 250716A: Swift-XRT afterglow detection
  63. GRB 250716A: GOTO tentative optical counterpart candidate
  64. GRB 250714A: SVOM/GRM observation
  65. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  66. GRB 250713A: Mephisto optical upper limits
  67. GRB 250713A: SVOM/VT optical upper limit
  68. GRB 250713A: NOT optical upper limits
  69. GRB 250713A: OHP/T193 upper limit
  70. GRB 250713A: SVOM/C-GFT upper limit
  71. GRB 250706B/C: 7DT Follow-up Observations
  72. GRB 250713A: EP-FXT counterpart detection
  73. EP250711a: COLIBRÍ continuous optical observations
  74. GRB 250713A: JinShan optical upper limits
  75. GRB 250713A: SVOM detection of a long burst
  76. GRB 250711A: DDOTI Optical Upper Limit
  77. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  78. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  79. GRB 250711A: SVOM/GRM observation
  80. EP250711a: NOT optical counterpart candidate
  81. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  82. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  83. GRB 250704A: GRANDMA observations
  84. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  85. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  86. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  87. IceCube-250708A: No Candidates from WINTER
  88. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  89. EP250704a/GRB 250704B: 10 GHz VLA detection
  90. IceCube-250706A: No Candidates from WINTER
  91. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  92. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  93. EP250704a/GRB250704B : HCT optical and NIR upper limits
  94. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  95. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  96. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  97. GRB 250702F: radio detection with the VLA
  98. IceCube-250706A: EP-FXT follow-up observations
  99. GRB 250706B/C: Fermi-LAT detection
  100. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations

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