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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"

18694 results found.

  1. GRB 250331B: Enhanced Swift-XRT position
  2. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  3. GRB 250329B: Swift-XRT confirmation of fading
  4. GRB20250327B: 45th Parallel Observatory upper limit
  5. GRB 250328A: Swift/UVOT Detection
  6. GRB 250328A: Swift-XRT refined Analysis
  7. GRB 250330A: Fermi GBM Observation
  8. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  9. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  10. GRB 250331C: Prompt enhanced Swift-XRT position
  11. GRB 250331C: Swift detection of a burst
  12. GRB 250331B: Swift detection of a burst
  13. GRB 250330A: SVOM/VT optical upper limit
  14. GRB 250330A: BOOTES-7 early optical upper limit
  15. GRB 250330A: Swift/UVOT Upper Limits
  16. GRB 250330A: Swift-XRT afterglow detection
  17. GRB 250330A: Fermi GBM Final Localization
  18. GRB 250330A: Prompt Swift-XRT position
  19. GRB 250329B: Swift-XRT afterglow detection
  20. GRB 250330A: Swift detection of a burst
  21. Swift GRB250330.26: Global MASTER-Net observations report
  22. GRB 250329B: SVOM/C-GFT optical upper limit
  23. GRB 250329B: SVOM/VT optical upper limit
  24. GRB 250329A: Swift-XRT afterglow detection
  25. GRB 250328A: SVOM/C-GFT optical upper limit
  26. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  27. GRB 250327B: LCO optical counterpart detection
  28. GRB 250322A: GRANDMA/TNOT optical upper limits
  29. GRB 250327A: SVOM/VT upper limits on the XRT position
  30. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  31. GRB 250327A: Swift-XRT refined Analysis
  32. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  33. GRB 250327A: J-band observations with WINTER
  34. GRB 250327A: SVOM/VT optical candidate
  35. GRB 250327A: Fermi GBM observation
  36. Swift GRB 250327A: Global MASTER-Net observations report
  37. GRB 250327A: DDOTI Optical Observations
  38. GRB 250327A: COLIBRÍ optical upper limit
  39. GRB 250327A: Swift detection of a burst
  40. Konus-Wind detection of GRB 250322A (short)
  41. IPN triangulation of GRB 250322B
  42. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  43. GRB 250322A: Swift-BAT refined analysis
  44. GRB 250322A: Swift/UVOT Upper Limits
  45. GRB 250321B: Swift-XRT observations
  46. GRB 250322A: Swift-XRT refined Analysis
  47. GRB 250322A: AstroSat CZTI detection of a short burst
  48. GRB250322A: STEP/T80S optical limits
  49. GRB 250322A: VLT optical observations
  50. GRB 250322A: VLT near-infrared observations
  51. GRB 250322A: NOT optical upper limits
  52. GRB 250322A: Enhanced Swift-XRT position
  53. GRB 250322A: MASTER optical observation
  54. GRB 250322A: Swift detection of a short burst
  55. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  56. GRB 250225B: GECAM-A detection
  57. GRB 250312A: GECAM-A detection
  58. GRB 250321B: Swift ToO observations
  59. GRB 250321A: Swift-BAT refined analysis
  60. GRB 250321A: Swift-XRT refined Analysis
  61. GRB 250320B: Fermi-LAT detection
  62. GRB 250321A: Swift/UVOT Upper Limits
  63. EP250321a: LCO optical counterpart detection
  64. EP250321a: Swift-XRT detection of an X-ray source
  65. Swift GRB 250321A: Global MASTER-Net observations report
  66. GRB 250321A: GOTO optical upper limits
  67. GRB 250321A: Swift-XRT localisation
  68. GRB 250321A: Fermi GBM Observation
  69. GRB 250321A: Swift detection of a burst
  70. GRB250312A: Swift/UVOT Upper Limits
  71. GRB 250317B: Swift-XRT observations
  72. GRB 250316A: Swift/UVOT Upper Limits
  73. GRB 250314A: REM optical/NIR upper limits
  74. GRB 250316A: AbAO AS-32 Optical Upper Limit
  75. GRB 250316A: Swift-XRT afterglow detection
  76. GRB 250316A: Fermi GBM Observation
  77. GRB 250316A: Swift-XRT observations
  78. GRB 250316A: Swift ToO observations
  79. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  80. GRB 250314A: EP-FXT afterglow detection
  81. GRB 250314A: Swift/UVOT Upper Limits
  82. GRB 250312B: GRBAlpha detection
  83. GRB 250314A: Swift XRT Detection
  84. GRB 250314A: NOT near-infrared candidate counterpart
  85. GRB 250312B: Fermi GBM Observation
  86. GRB 250313A: Swift-XRT observations
  87. Konus-Wind detection of GRB 250308A
  88. GRB 250313A: Fermi-LAT detection
  89. GRB 250313A: Swift ToO observations
  90. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  91. EP250304a: SVOM/VT optical observation
  92. EP250302a: Chandra X-ray Detection
  93. GRB 250312A: Swift-XRT refined Analysis
  94. GRB 250312A: Enhanced Swift-XRT position
  95. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  96. GRB 250226B: Fermi GBM Observation
  97. Swift GRB 250312A: Global MASTER-Net observations report
  98. GRB 250302A: Fermi GBM Observation
  99. GRB 250312A: Swift detection of a burst
  100. GRB 250223B: Fermi GBM Observation

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