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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').
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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.

Advanced Search Examples (click to copy):

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

35982 results found.

  1. GRB 250805A: Enhanced Swift-XRT position
  2. GRB 250804C: AstroSat CZTI detection of a long burst
  3. GRB 250805A: TRT optical upper limits
  4. GRB 250805A: Swift-XRT observations
  5. GRB 250805A: Swift detection of a burst
  6. GRB 250804B: Tiled Swift observations
  7. GRB 250804B: SVOM/GRM observation of a short burst
  8. GRB 250804A: Fermi GBM Final Localization
  9. Fermi Gamma-ray Burst Monitor trigger 775945985/250803856 is not a GRB
  10. GRB 250702B: SMA observations
  11. EP250711a: CrAO and Assy optical observations
  12. GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
  13. LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
  14. LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO
  15. LIGO/Virgo/KAGRA S250727dc: Upper limits from Swift/BAT-GUANO
  16. GRB 250725A: AstroSat CZTI detection
  17. GRB 250727A: EP-FXT follow-up observation
  18. GRB 250725A: PRIME near-infrared observations
  19. GRB: Clarification on Gamma-Ray Burst Naming Convention
  20. GRB 250728A: Swift-XRT observations
  21. GRB 250727A: SVOM/ECLAIRs refined analysis
  22. GRB 250728A: COLIBRÍ optical upper limit
  23. GRB 250728A: Fermi GBM Observation
  24. GRB 250728A: Swift ToO observations
  25. GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
  26. GRB 250727A: AST3-2 Upper limit
  27. GRB 250727A: EP-FXT counterpart detection
  28. GRB250727A: SVOM/VT optical upper limit
  29. GRB 250727A: Swift-XRT observations
  30. GRB 250727A: SVOM detection of a burst
  31. GRB 250725A: Swift-XRT refined Analysis
  32. GRB 250725A: Fermi GBM Observation
  33. GRB 250725A: Swift-BAT refined analysis
  34. Konus-Wind detection of GRB 250725A
  35. GRB 250725A: SVOM/GRM observation
  36. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  37. GRB 250725A: Swift/UVOT Upper Limits
  38. GRB 250725A: Fermi-LAT detection
  39. GRB 250725A: VLT/FORS2 spectroscopic redshift z = 5.26
  40. GRB 250725A: BOOTES-7 early optical detection
  41. GRB 250725A: SVOM/VT optical candidate
  42. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  43. GRB 250725A: Enhanced Swift-XRT position
  44. GRB 250725A: Swift detection of a burst
  45. Swift GRB 250725A: Global MASTER-Net OT detection
  46. GRB 250725A: Fermi GBM Final Real-time Localization
  47. Fermi GRB 250725A: Global MASTER-Net observations report
  48. Swift GRB 250725A: Global MASTER-Net observations report
  49. GRB 250723B: Fermi GBM Final Real-time Localization
  50. GRB 250721A: Fermi GBM Observation
  51. GRB 250723A: Fermi GBM Final Real-time Localization
  52. Swift-BAT trigger 1334535 is not a GRB
  53. GRB 250721A: Swift-XRT observations
  54. GRB 250722A: Fermi GBM Final Real-time Localization
  55. GRB 250713A : SVOM/ECLAIRs refined analysis
  56. GRB 250717B: SVOM/GRM observation
  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. GRB 250721A: MAXI/GSC detection
  60. GRB 250721A: Fermi GBM Final Localization
  61. GRB 250720B: Fermi GBM Final Localization Correction
  62. GRB 250720A: Fermi GBM Final Localization
  63. LIGO/Virgo/KAGRA S250720j: Retraction of GW compact binary merger candidate
  64. Fermi Gamma-ray Burst Monitor trigger 774670514/250720094 is not a GRB
  65. GRB 250717B: COLIBRÍ optical upper limit
  66. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  67. GRB 250717B: Swift-XRT observations
  68. GRB 250718B: Fermi GBM Final Localization Correction
  69. GRB 250718B: Fermi GBM Final Real-time Localization
  70. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  71. Swift Trigger 1334535: a possible GRB 250718A
  72. GRB 250717B: Swift ToO observations
  73. GRB 270713A: Kitab and AbAO Optical Observations
  74. GRB 250717B: Fermi GBM Observation
  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: GOTO tentative optical counterpart candidate
  83. GRB 250716A: Fermi GBM Observation
  84. GRB 250714A: SVOM/GRM observation
  85. Fermi GRB 250716A: Global MASTER-Net observations report
  86. GRB 250716A: Fermi GBM Final Real-time Localization
  87. Fermi GRB 250715A: Global MASTER-Net observations report
  88. GRB 250715A: Fermi GBM Final Real-time Localization
  89. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  90. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  91. GRB 250713A: Mephisto optical upper limits
  92. Fermi GRB 250714A: Global MASTER-Net observations report
  93. GRB 250713A: SVOM/VT optical upper limit
  94. GRB 250713A: NOT optical upper limits
  95. GRB 250713A: OHP/T193 upper limit
  96. GRB 250713A: SVOM/C-GFT upper limit
  97. GRB 250714A: Fermi GBM Final Real-time Localization
  98. GRB 250706B/C: 7DT Follow-up Observations
  99. GRB 250713A: Swift-XRT observations
  100. GRB 250713A: EP-FXT counterpart detection

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