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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"

19193 results found.

  1. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  2. GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
  3. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT follow up of AT 2025smm
  4. LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
  5. LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO
  6. LIGO/Virgo/KAGRA S250727dc: Upper limits from Swift/BAT-GUANO
  7. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  8. GRB 250725A: AstroSat CZTI detection
  9. GRB 250727A: EP-FXT follow-up observation
  10. GRB 250725A: PRIME near-infrared observations
  11. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  12. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  13. GRB 250728A: Swift-XRT observations
  14. GRB 250728A: COLIBRÍ optical upper limit
  15. GRB 250728A: Fermi GBM Observation
  16. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT detection of a new source, AT 2025smm
  17. GRB 250728A: Swift ToO observations
  18. GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
  19. GRB 250727A: EP-FXT counterpart detection
  20. GRB250727A: SVOM/VT optical upper limit
  21. GRB 250727A: Swift-XRT observations
  22. Swift detection of the Soft Gamma Repeater PSR J1647-4552
  23. GRB 250725A: Swift-XRT refined Analysis
  24. GRB 250725A: Fermi GBM Observation
  25. GRB 250725A: Swift-BAT refined analysis
  26. Konus-Wind detection of GRB 250725A
  27. GRB 250725A: SVOM/GRM observation
  28. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  29. GRB 250725A: Swift/UVOT Upper Limits
  30. GRB 250725A: Fermi-LAT detection
  31. GRB 250725A: BOOTES-7 early optical detection
  32. GRB 250725A: SVOM/VT optical candidate
  33. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  34. GRB 250725A: Enhanced Swift-XRT position
  35. GRB 250725A: Swift detection of a burst
  36. Swift GRB 250725A: Global MASTER-Net OT detection
  37. Swift GRB 250725A: Global MASTER-Net observations report
  38. SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
  39. Swift-BAT trigger 1334535 is not a GRB
  40. GRB 250721A: Swift-XRT observations
  41. GRB 250717B: SVOM/GRM observation
  42. GRB 250721A: Tiled Swift observations
  43. GRB 250717B: COLIBRÍ optical upper limit
  44. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  45. GRB 250717B: Swift-XRT observations
  46. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  47. Swift Trigger 1334535: a possible GRB 250718A
  48. Swift GRB250718.01: Global MASTER-Net observations report
  49. GRB 250717B: Swift ToO observations
  50. GRB 270713A: Kitab and AbAO Optical Observations
  51. GRB 250717B: Fermi GBM Observation
  52. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  53. GRB 250716A: Swift-XRT afterglow detection
  54. GRB 250716A: Swift ToO observations
  55. GRB 250713A: SVOM/C-GFT upper limit
  56. GRB 250713A: Swift-XRT observations
  57. GRB 250706A: Swift-BAT refined analysis
  58. GRB 250702F: Swift-BAT refined analysis
  59. GRB 250628A: Swift-BAT refined analysis
  60. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  61. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  62. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  63. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  64. GRB 250706B/C: Fermi-LAT detection
  65. GRB 250706B: Swift/UVOT Detection
  66. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  67. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  68. GRB 250702F: GRANDMA observations
  69. GRB 250706A: Swift-XRT refined Analysis
  70. GRB 250706A: Swift/UVOT Upper Limits
  71. GRB 250706A: REM optical/NIR observations
  72. Swift GRB 250706A: Global MASTER-Net observations report
  73. GRB 250706A: JinShan optical upper limits
  74. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  75. GRB250706B: Swift-XRT counterpart detection
  76. GRB 250706A: GROWTH-India Telescope optical upper limit
  77. GRB 250706A: Swift detection of a burst
  78. GRB 250704B: Swift-XRT refined Analysis
  79. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  80. GRB 250704B: Swift/UVOT Upper Limits
  81. GRB 250704A: Swift/UVOT Detection
  82. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  83. GRB 250702F: Kilonova-Catcher optical afterglow detection
  84. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  85. GRB 250704A: SVOM/VT optical observation
  86. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  87. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  88. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  89. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  90. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  91. EP250704a / GRB250704B: Swift-XRT counterpart detection
  92. GRB 250704A: Swift-XRT afterglow detection
  93. GRB 250702B / EP2050702a: FTW optical and NIR observations
  94. Konus-Wind detection of GRB 250702F
  95. GRB 250702F: GROWTH-India Telescope optical observations
  96. EP250702a: WFST optical observations
  97. GRB 250702F: SVOM/VT optical observation
  98. GRB 250702F: Swift/UVOT Detection
  99. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  100. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit

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