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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.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

27475 results found.

  1. GRB 250806A: Swift-XRT counterpart detection
  2. EP250806a: Einstein Probe detection of an X-ray transient
  3. GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  4. GRB 250806A: SVOM detection of a soft burst
  5. GRB 250805A: SVOM/VT optical counterpart
  6. GRB 250805A: ESO/VLT observations
  7. GRB 250805A: Swift-XRT refined Analysis
  8. GRB 250804B: Swift-XRT observations
  9. GRB 250805A: Enhanced Swift-XRT position
  10. GRB 250804C: AstroSat CZTI detection of a long burst
  11. GRB 250805A: TRT optical upper limits
  12. IceCube-250804A - IceCube observation of a high-energy neutrino candidate track-like event
  13. GRB 250805A: Swift-XRT observations
  14. GRB 250805A: Swift detection of a burst
  15. GRB 250804B: Tiled Swift observations
  16. GRB 250804A: Fermi GBM Final Localization
  17. EP250802a: additional Liverpool Telescope upper limits
  18. EP250802a: GROWTH-India Telescope optical upper limit
  19. EP250802a: Einstein Probe detection of an X-ray transient
  20. LIGO/Virgo/KAGRA S250725j: GOTO pre-trigger detection of AT2025sib
  21. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  22. GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
  23. EP250730a: Einstein Probe detection of an X-ray transient
  24. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  25. GRB 250725A: AstroSat CZTI detection
  26. GRB 250727A: EP-FXT follow-up observation
  27. GRB 250725A: PRIME near-infrared observations
  28. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  29. GRB: Clarification on Gamma-Ray Burst Naming Convention
  30. GRB 250728A: Swift-XRT observations
  31. EP-WXT trigger 01709195487: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  32. GRB 250728A: COLIBRÍ optical upper limit
  33. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT detection of a new source, AT 2025smm
  34. GRB 250728A: Swift ToO observations
  35. GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
  36. GRB 250727A: AST3-2 Upper limit
  37. GRB 250727A: EP-FXT counterpart detection
  38. GRB250727A: SVOM/VT optical upper limit
  39. GRB 250727A: Swift-XRT observations
  40. GRB 250727A: SVOM detection of a burst
  41. Swift detection of the Soft Gamma Repeater PSR J1647-4552
  42. GRB 250725A: Swift-XRT refined Analysis
  43. GRB 250725A: Fermi GBM Observation
  44. Konus-Wind detection of GRB 250725A
  45. GRB 250725A: Swift/UVOT Upper Limits
  46. GRB 250725A: Fermi-LAT detection
  47. GRB 250725A: VLT/FORS2 spectroscopic redshift z = 5.26
  48. GRB 250725A: BOOTES-7 early optical detection
  49. GRB 250725A: SVOM/VT optical candidate
  50. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  51. GRB 250725A: Enhanced Swift-XRT position
  52. GRB 250725A: Swift detection of a burst
  53. Swift GRB 250725A: Global MASTER-Net OT detection
  54. GRB 250725A: Fermi GBM Final Real-time Localization
  55. EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
  56. EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz
  57. SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
  58. GRB 250723B: Fermi GBM Final Real-time Localization
  59. GRB 250723A: Fermi GBM Final Real-time Localization
  60. SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
  61. GRB 250721A: Swift-XRT observations
  62. GRB 250722A: Fermi GBM Final Real-time Localization
  63. GRB 250721A: Tiled Swift observations
  64. GRB 250721A: MAXI/GSC detection
  65. GRB 250721A: Fermi GBM Final Localization
  66. GRB 250720B: Fermi GBM Final Localization Correction
  67. GRB 250720A: Fermi GBM Final Localization
  68. GRB 250717B: COLIBRÍ optical upper limit
  69. GRB 250717B: Swift-XRT observations
  70. GRB 250718B: Fermi GBM Final Localization Correction
  71. GRB 250718B: Fermi GBM Final Real-time Localization
  72. Swift Trigger 1334535: a possible GRB 250718A
  73. GRB 250717B: Swift ToO observations
  74. GRB 270713A: Kitab and AbAO Optical Observations
  75. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  76. Konus-Wind detection of GRB 250716A
  77. GRB 250716A: Swift-XRT afterglow detection
  78. GRB 250717B: Fermi GBM Final Real-time Localization
  79. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  80. GRB 250717A: Fermi GBM Final Real-time Localization
  81. GRB 250716A: Swift ToO observations
  82. GRB 250716A: Fermi GBM Final Real-time Localization
  83. GRB 250715A: Fermi GBM Final Real-time Localization
  84. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  85. GRB 250713A: SVOM/VT optical upper limit
  86. GRB 250713A: SVOM/C-GFT upper limit
  87. GRB 250714A: Fermi GBM Final Real-time Localization
  88. GRB 250706B/C: 7DT Follow-up Observations
  89. GRB 250713A: Swift-XRT observations
  90. GRB 250713A: EP-FXT counterpart detection
  91. GRB 250713A: SVOM detection of a long burst
  92. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  93. GRB 250711A: Fermi GBM Final Real-time Localization
  94. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  95. GRB 250704B / EP250704a: 1.3 GHz MeerKAT Detection
  96. GRB 250702B,D,E / EP250702a: ALMA detection
  97. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  98. GRB 250709A: Fermi GBM Final Localization
  99. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  100. GRB 250706B/C: Insight-HXMT detection

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