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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"

23413 results found.

  1. GRB 250804B: Swift-XRT observations
  2. GRB 250805A: Enhanced Swift-XRT position
  3. GRB 250805A: TRT optical upper limits
  4. GRB 250805A: Swift-XRT observations
  5. GRB 250805A: Swift detection of a burst
  6. GRB 250804B: SVOM/GRM observation of a short burst
  7. EP250802a: additional Liverpool Telescope upper limits
  8. EP250730a: SVOM/VT optical upper limit
  9. EP250802a: Liverpool Telescope optical upper limits
  10. EP250802a: GROWTH-India Telescope optical upper limit
  11. LIGO/Virgo/KAGRA S250802dn: Identification of a GW compact binary merger candidate
  12. LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
  13. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS candidates
  14. LIGO/Virgo/KAGRA S250725j: GOTO pre-trigger detection of AT2025sib
  15. EP250711a: CrAO and Assy optical observations
  16. EP250730a: COLIBRÍ optical upper limit
  17. GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
  18. LIGO/Virgo/KAGRA S250725j: DECam DESGW Epoch 1-2 Candidates
  19. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT follow up of AT 2025smm
  20. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  21. GRB 250727A: EP-FXT follow-up observation
  22. GRB 250725A: PRIME near-infrared observations
  23. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  24. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  25. GRB 250728A: Swift-XRT observations
  26. GRB 250728A: COLIBRÍ optical upper limit
  27. GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
  28. GRB 250727A: EP-FXT counterpart detection
  29. GRB250727A: SVOM/VT optical upper limit
  30. GRB 250727A: Swift-XRT observations
  31. LIGO/Virgo/KAGRA S250727dc: Identification of a GW compact binary merger candidate
  32. LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
  33. LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
  34. GRB 250727A: SVOM detection of a burst
  35. Swift detection of the Soft Gamma Repeater PSR J1647-4552
  36. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  37. GRB 250725A: Swift-XRT refined Analysis
  38. LIGO/Virgo/KAGRA S250725j: NED Galaxies in the 3-Initial Localization Volume
  39. GRB 250725A: SVOM/GRM observation
  40. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  41. GRB 250725A: Swift/UVOT Upper Limits
  42. GRB 250725A: SVOM/VT optical candidate
  43. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate
  44. LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
  45. GRB 250725A: Enhanced Swift-XRT position
  46. GRB 250725A: Swift detection of a burst
  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: Swift XRT/UVOT upper limits
  52. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  53. GRB 250721A: Swift-XRT observations
  54. GRB 250717B: SVOM/GRM observation
  55. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  56. EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
  57. GRB 250717B: COLIBRÍ optical upper limit
  58. GRB 250717B: Swift-XRT observations
  59. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  60. Swift Trigger 1334535: a possible GRB 250718A
  61. GRB 270713A: Kitab and AbAO Optical Observations
  62. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  63. GRB 250716A: Swift-XRT afterglow detection
  64. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  65. GRB 250714A: SVOM/GRM observation
  66. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  67. GRB 250713A: Mephisto optical upper limits
  68. GRB 250713A: SVOM/VT optical upper limit
  69. GRB 250713A: NOT optical upper limits
  70. GRB 250713A: OHP/T193 upper limit
  71. GRB 250713A: SVOM/C-GFT upper limit
  72. GRB 250706B/C: 7DT Follow-up Observations
  73. GRB 250713A: Swift-XRT observations
  74. GRB 250713A: EP-FXT counterpart detection
  75. EP250711a: COLIBRÍ continuous optical observations
  76. GRB 250702F: Swift-BAT refined analysis
  77. GRB 250713A: JinShan optical upper limits
  78. GRB 250713A: SVOM detection of a long burst
  79. GRB 250711A: DDOTI Optical Upper Limit
  80. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  81. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  82. GRB 250711A: SVOM/GRM observation
  83. EP250711a: NOT optical counterpart candidate
  84. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  85. Fermi GRB 250711A: Global MASTER-Net observations report
  86. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  87. GRB 250704A: GRANDMA observations
  88. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  89. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  90. IceCube-250708A: No Candidates from WINTER
  91. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  92. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  93. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  94. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  95. EP250704a/GRB 250704B: 10 GHz VLA detection
  96. IceCube-250706A: No Candidates from WINTER
  97. IPN triangulation of GRB 250706C (consistent with the GRB 250706B)
  98. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  99. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  100. EP250704a/GRB250704B : HCT optical and NIR upper limits

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