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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"

18785 results found.

  1. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  2. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  3. GRB 250702F: Enhanced Swift-XRT position
  4. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  5. GRB 250702F: NOT observations of the optical afterglow
  6. GRB 250702F: MASTER optical afterglow observation
  7. GRB 250702F: GOTO optical counterpart detection
  8. GRB 250702F: Ondrejov D50 optical afterglow detection
  9. GRB 250702F: Swift detection of a burst with an optical counterpart
  10. Swift GRB 250702F: Global MASTER-Net observations report
  11. GRB 250628B: Swift-XRT observations
  12. GRB 250628B: SVOM/VT optical upper limit
  13. GRB 250628A: REM optical/NIR upper limits
  14. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  15. GRB 250628A: VLT/X-shooter upper limits
  16. GRB 250628A: Swift/UVOT Upper Limits
  17. GRB 250628A: Swift-XRT refined Analysis
  18. Swift GRB 250628A: Global MASTER-Net observations report
  19. GRB 250628A: Enhanced Swift-XRT position
  20. GRB 250628A: Swift detection of a burst
  21. GRB 250625A: Swift-BAT refined analysis
  22. GRB 250625A: Leavitt Observatory afterglow detection
  23. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  24. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  25. GRB 250625A: SVOM/C-GFT upper limit in early phase
  26. GRB 250625A: GECAM-B detection
  27. GRB 250625A: Swift/UVOT Upper Limits
  28. GRB 250625A: ABObservatory afterglow detection
  29. GRB 250625A: COLIBRÍ optical observations
  30. GRB 250625A: Fermi-LAT detection
  31. GRB 250625A: Swift-XRT refined Analysis
  32. GRB 250625A: JinShan optical observations
  33. GRB250625A: Fermi GBM Observation
  34. Swift GRB 250625A: Global MASTER-Net observations report
  35. GRB 250625A: SVOM/VT optical confirmation
  36. GRB 250620B: Fermi GBM Observation
  37. GRB 250625A: Enhanced Swift-XRT position
  38. GRB 250625A: Swift detection of a burst
  39. GRB 250620A: AstroSat CZTI detection
  40. GRB 241018A: Maidanak optical observations
  41. GRB 250617B: Swift-BAT refined analysis
  42. IPN triangulation of GRB 250620С (long/bright)
  43. GRB 250620A: SVOM/GRM observation of a short burst
  44. GRB250620A: Fermi GBM Observation
  45. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  46. GRB 250619B: Fermi GBM Observation
  47. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  48. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  49. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  50. GRB 250615A: Kilonova-Catcher optical upper limits
  51. GRB 250617B: Assy AZT-20 Optical Observations
  52. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  53. GRB 250615A/EP250615a: FTW optical and NIR observations
  54. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  55. GRB 250617B: Swift/UVOT Detection
  56. GRB 250617B: Kilonova-Catcher optical afterglow detection
  57. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  58. GRB 250617B: NOT NIR observations of the afterglow
  59. GRB 250617B: Swift-XRT refined Analysis
  60. GRB 250617B: SVOM/VT optical observation
  61. Swift GRB 250617B: Global MASTER-Net observations report
  62. GRB 250617B: GOTO optical upper limit
  63. GRB 250617B: Enhanced Swift-XRT position
  64. GRB 250617B: Fermi GBM Observation
  65. GRB 250615A: Swift-BAT refined analysis
  66. GRB 250617B: Fermi GBM Final Localization
  67. GRB 250617B: Ondrejov D50 optical afterglow detection
  68. GRB 250617B: Swift detection of a burst with an optical counterpart
  69. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  70. EP#01709178975: Swift-XRT counterpart detection
  71. Konus-Wind detection of GRB 250615A / EP250615a
  72. GRB 250615A / EP250615a: AstroSat CZTI detection
  73. GRB 250615A: COLIBRÍ optical upper limit
  74. GRB 250615A: DDOTI Optical Upper Limit
  75. GRB 250615A: Swift/UVOT Upper Limits
  76. GRB 250615A: Swift-XRT refined Analysis
  77. GRB 250615A: Enhanced Swift-XRT position
  78. GRB 250615A: Prompt enhanced Swift-XRT position
  79. GRB 250615A: Swift detection of a burst
  80. Swift GRB 250615A: Global MASTER-Net observations report
  81. sb25061207: Mephisto optical upper limits
  82. sb25061218: Swift-XRT observations
  83. sb25061207: EP-FXT follow-up observation and afterglow candidate
  84. sb25061207: Swift-XRT observations
  85. GRB 250610B: Swift-XRT refined Analysis
  86. EP250610a: continuous follow-up observations with EP-FXT
  87. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  88. Swift GRB250612.04: Global MASTER-Net observations report
  89. GRB 250610B: Swift/UVOT Detection
  90. EP250610A: Swift/UVOT Upper limits
  91. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  92. GRB 250610B: Swift-XRT counterpart detection
  93. GRB 250610B: SVOM/VT optical counterpart
  94. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  95. GRB 250605A: Swift-BAT refined analysis
  96. EP250610a: SVOM/VT optical upper limit
  97. EP250610a: REM optical/NIR observations
  98. GRB 250609A: Fermi GBM Observation
  99. EP250610a: Swift-XRT counterpart detection
  100. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst

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