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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"

39163 results found.

  1. GRB 250805A: SVOM/VT optical counterpart
  2. GRB 250805A: ESO/VLT observations
  3. GRB 250805A: Swift-XRT refined Analysis
  4. GRB 250804B: Swift-XRT observations
  5. GRB 250805A: Enhanced Swift-XRT position
  6. GRB 250804C: AstroSat CZTI detection of a long burst
  7. GRB 250805A: TRT optical upper limits
  8. IceCube-250804A - IceCube observation of a high-energy neutrino candidate track-like event
  9. GRB 250805A: Swift-XRT observations
  10. GRB 250805A: Swift detection of a burst
  11. Swift GRB250805.26: Global MASTER-Net observations report
  12. GRB 250804B: Tiled Swift observations
  13. Fermi trigger No 776041355: Global MASTER-Net observations report
  14. GRB 250804B: SVOM/GRM observation of a short burst
  15. GRB 250804A: Fermi GBM Final Localization
  16. Fermi Gamma-ray Burst Monitor trigger 775945985/250803856 is not a GRB
  17. EP250802a: Global MASTER-Net observations report
  18. EP250802a: GROWTH-India Telescope optical upper limit
  19. GRB 250702B: SMA observations
  20. EP250711a: CrAO and Assy optical observations
  21. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  22. EP250730a: Global MASTER-Net observations report
  23. EP250730a: COLIBRÍ optical upper limit
  24. GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
  25. LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
  26. LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO
  27. LIGO/Virgo/KAGRA S250727dc: Upper limits from Swift/BAT-GUANO
  28. GRB 250725A: AstroSat CZTI detection
  29. GRB 250727A: EP-FXT follow-up observation
  30. GRB 250725A: PRIME near-infrared observations
  31. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  32. GRB: Clarification on Gamma-Ray Burst Naming Convention
  33. GRB 250728A: Swift-XRT observations
  34. GRB 250727A: SVOM/ECLAIRs refined analysis
  35. GRB 250728A: COLIBRÍ optical upper limit
  36. GRB 250728A: Fermi GBM Observation
  37. Fermi trigger No 775387550: Global MASTER-Net observations report
  38. GRB 250728A: Swift ToO observations
  39. GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
  40. GRB 250727A: AST3-2 Upper limit
  41. GRB 250727A: EP-FXT counterpart detection
  42. GRB250727A: SVOM/VT optical upper limit
  43. GRB 250727A: Swift-XRT observations
  44. GRB 250727A: SVOM detection of a burst
  45. Swift detection of the Soft Gamma Repeater PSR J1647-4552
  46. GRB 250725A: Swift-XRT refined Analysis
  47. GRB 250725A: Fermi GBM Observation
  48. GRB 250725A: Swift-BAT refined analysis
  49. Konus-Wind detection of GRB 250725A
  50. GRB 250725A: SVOM/GRM observation
  51. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  52. GRB 250725A: Swift/UVOT Upper Limits
  53. GRB 250725A: Fermi-LAT detection
  54. GRB 250725A: VLT/FORS2 spectroscopic redshift z = 5.26
  55. GRB 250725A: BOOTES-7 early optical detection
  56. GRB 250725A: SVOM/VT optical candidate
  57. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  58. GRB 250725A: Enhanced Swift-XRT position
  59. GRB 250725A: Swift detection of a burst
  60. Swift GRB 250725A: Global MASTER-Net OT detection
  61. GRB 250725A: Fermi GBM Final Real-time Localization
  62. Fermi GRB 250725A: Global MASTER-Net observations report
  63. Swift GRB 250725A: Global MASTER-Net observations report
  64. GRB 250723B: Fermi GBM Final Real-time Localization
  65. GRB 250721A: Fermi GBM Observation
  66. GRB 250723A: Fermi GBM Final Real-time Localization
  67. Swift-BAT trigger 1334535 is not a GRB
  68. GRB 250721A: Swift-XRT observations
  69. GRB 250722A: Fermi GBM Final Real-time Localization
  70. GRB 250713A : SVOM/ECLAIRs refined analysis
  71. GRB 250717B: SVOM/GRM observation
  72. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  73. GRB 250721A: Tiled Swift observations
  74. GRB 250721A: MAXI/GSC detection
  75. GRB 250721A: Fermi GBM Final Localization
  76. GRB 250720B: Fermi GBM Final Localization Correction
  77. GRB 250720A: Fermi GBM Final Localization
  78. Fermi trigger No 774730635: Global MASTER-Net observations report
  79. LIGO/Virgo/KAGRA S250720j: Retraction of GW compact binary merger candidate
  80. Fermi Gamma-ray Burst Monitor trigger 774670514/250720094 is not a GRB
  81. GRB 250717B: COLIBRÍ optical upper limit
  82. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  83. GRB 250717B: Swift-XRT observations
  84. GRB 250718B: Fermi GBM Final Localization Correction
  85. GRB 250718B: Fermi GBM Final Real-time Localization
  86. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  87. Swift Trigger 1334535: a possible GRB 250718A
  88. Swift GRB250718.01: Global MASTER-Net observations report
  89. GRB 250717B: Swift ToO observations
  90. GRB 270713A: Kitab and AbAO Optical Observations
  91. GRB 250717B: Fermi GBM Observation
  92. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  93. Konus-Wind detection of GRB 250716A
  94. GRB 250716A: Swift-XRT afterglow detection
  95. GRB 250717B: Fermi GBM Final Real-time Localization
  96. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  97. GRB 250717A: Fermi GBM Final Real-time Localization
  98. GRB 250716A: Swift ToO observations
  99. GRB 250716A: GOTO tentative optical counterpart candidate
  100. GRB 250716A: Fermi GBM Observation

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