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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

37934 results found.

  1. GRB 250807B: Enhanced Swift-XRT position
  2. Swift GRB250807.65: Global MASTER-Net observations report
  3. GRB 250807A: Enhanced Swift-XRT position
  4. GRB 250807B: Swift detection of a burst with an optical counterpart.
  5. GRB 250805A: Kilonova-Catcher optical upper limits
  6. GRB 250805A: Swift/UVOT Upper Limits
  7. GRB 250806A: Swift/UVOT U-band detection
  8. GRB 250807A: Swift detection of a burst with an optical counterpart
  9. GRB 250806A: EP-FXT observation
  10. EP#01709198415/EP250806a: Swift-XRT observations
  11. GRB 250806A: J-band upper limit from WINTER
  12. GRB 250805A: Swift-BAT refined analysis
  13. GRB 250806A: KAIT optical upper limit
  14. GRB 250806A: SVOM/VT refined analysis
  15. GRB 250806A: Swift-XRT counterpart detection
  16. GRB 250806A: Kilonova-Catcher optical upper limits
  17. GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  18. GRB 250806A: SVOM/VT optical upper limit
  19. GRB 250806A: SVOM detection of a soft burst
  20. GRB 250805A: SVOM/VT optical counterpart
  21. GRB 250805A: ESO/VLT observations
  22. GRB 250805A: Swift-XRT refined Analysis
  23. GRB 250804B: Swift-XRT observations
  24. GRB 250805A: Enhanced Swift-XRT position
  25. GRB 250804C: AstroSat CZTI detection of a long burst
  26. GRB 250805A: TRT optical upper limits
  27. GRB 250805A: Swift-XRT observations
  28. GRB 250805A: Swift detection of a burst
  29. Swift GRB250805.26: Global MASTER-Net observations report
  30. GRB 250804B: Tiled Swift observations
  31. GRB 250804B: SVOM/GRM observation of a short burst
  32. GRB 250804A: Fermi GBM Final Localization
  33. Fermi Gamma-ray Burst Monitor trigger 775945985/250803856 is not a GRB
  34. LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
  35. GRB 250702B: SMA observations
  36. EP250711a: CrAO and Assy optical observations
  37. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  38. GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
  39. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT follow up of AT 2025smm
  40. LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
  41. LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO
  42. LIGO/Virgo/KAGRA S250727dc: Upper limits from Swift/BAT-GUANO
  43. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  44. GRB 250725A: AstroSat CZTI detection
  45. GRB 250727A: EP-FXT follow-up observation
  46. GRB 250725A: PRIME near-infrared observations
  47. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  48. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  49. GRB: Clarification on Gamma-Ray Burst Naming Convention
  50. GRB 250728A: Swift-XRT observations
  51. GRB 250727A: SVOM/ECLAIRs refined analysis
  52. GRB 250728A: COLIBRÍ optical upper limit
  53. GRB 250728A: Fermi GBM Observation
  54. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT detection of a new source, AT 2025smm
  55. GRB 250728A: Swift ToO observations
  56. GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
  57. GRB 250727A: AST3-2 Upper limit
  58. GRB 250727A: EP-FXT counterpart detection
  59. GRB250727A: SVOM/VT optical upper limit
  60. GRB 250727A: Swift-XRT observations
  61. GRB 250727A: SVOM detection of a burst
  62. Swift detection of the Soft Gamma Repeater PSR J1647-4552
  63. GRB 250725A: Swift-XRT refined Analysis
  64. GRB 250725A: Fermi GBM Observation
  65. GRB 250725A: Swift-BAT refined analysis
  66. Konus-Wind detection of GRB 250725A
  67. GRB 250725A: SVOM/GRM observation
  68. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  69. GRB 250725A: Swift/UVOT Upper Limits
  70. GRB 250725A: Fermi-LAT detection
  71. GRB 250725A: VLT/FORS2 spectroscopic redshift z = 5.26
  72. GRB 250725A: BOOTES-7 early optical detection
  73. GRB 250725A: SVOM/VT optical candidate
  74. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  75. GRB 250725A: Enhanced Swift-XRT position
  76. GRB 250725A: Swift detection of a burst
  77. Swift GRB 250725A: Global MASTER-Net OT detection
  78. GRB 250725A: Fermi GBM Final Real-time Localization
  79. Fermi GRB 250725A: Global MASTER-Net observations report
  80. Swift GRB 250725A: Global MASTER-Net observations report
  81. GRB 250723B: Fermi GBM Final Real-time Localization
  82. GRB 250721A: Fermi GBM Observation
  83. GRB 250723A: Fermi GBM Final Real-time Localization
  84. SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
  85. Swift-BAT trigger 1334535 is not a GRB
  86. GRB 250721A: Swift-XRT observations
  87. GRB 250722A: Fermi GBM Final Real-time Localization
  88. GRB 250713A : SVOM/ECLAIRs refined analysis
  89. GRB 250717B: SVOM/GRM observation
  90. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  91. GRB 250721A: Tiled Swift observations
  92. GRB 250721A: MAXI/GSC detection
  93. GRB 250721A: Fermi GBM Final Localization
  94. GRB 250720B: Fermi GBM Final Localization Correction
  95. GRB 250720A: Fermi GBM Final Localization
  96. LIGO/Virgo/KAGRA S250720j: Retraction of GW compact binary merger candidate
  97. Fermi Gamma-ray Burst Monitor trigger 774670514/250720094 is not a GRB
  98. GRB 250717B: COLIBRÍ optical upper limit
  99. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  100. GRB 250717B: Swift-XRT observations

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