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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"

19624 results found.

  1. GRB 250327A: Fermi GBM observation
  2. Swift GRB 250327A: Global MASTER-Net observations report
  3. GRB 250327A: DDOTI Optical Observations
  4. GRB 250327A: COLIBRÍ optical upper limit
  5. GRB 250327A: Swift detection of a burst
  6. Konus-Wind detection of GRB 250322A (short)
  7. IPN triangulation of GRB 250322B
  8. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  9. GRB 250322A: Swift-BAT refined analysis
  10. GRB 250322A: Swift/UVOT Upper Limits
  11. GRB 250321B: Swift-XRT observations
  12. GRB 250322A: Swift-XRT refined Analysis
  13. GRB 250322A: AstroSat CZTI detection of a short burst
  14. GRB250322A: STEP/T80S optical limits
  15. GRB 250322A: VLT optical observations
  16. GRB 250322A: VLT near-infrared observations
  17. GRB 250322A: NOT optical upper limits
  18. GRB 250322A: Enhanced Swift-XRT position
  19. GRB 250322A: MASTER optical observation
  20. GRB 250322A: Swift detection of a short burst
  21. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  22. GRB 250225B: GECAM-A detection
  23. GRB 250312A: GECAM-A detection
  24. GRB 250321B: Swift ToO observations
  25. GRB 250321A: Swift-BAT refined analysis
  26. GRB 250321A: Swift-XRT refined Analysis
  27. GRB 250320B: Fermi-LAT detection
  28. GRB 250321A: Swift/UVOT Upper Limits
  29. EP250321a: LCO optical counterpart detection
  30. EP250321a: Swift-XRT detection of an X-ray source
  31. Swift GRB 250321A: Global MASTER-Net observations report
  32. GRB 250321A: GOTO optical upper limits
  33. GRB 250321A: Swift-XRT localisation
  34. GRB 250321A: Fermi GBM Observation
  35. GRB 250321A: Swift detection of a burst
  36. GRB250312A: Swift/UVOT Upper Limits
  37. GRB 250317B: Swift-XRT observations
  38. GRB 250316A: Swift/UVOT Upper Limits
  39. GRB 250314A: REM optical/NIR upper limits
  40. GRB 250316A: AbAO AS-32 Optical Upper Limit
  41. GRB 250316A: Swift-XRT afterglow detection
  42. GRB 250316A: Fermi GBM Observation
  43. GRB 250316A: Swift-XRT observations
  44. GRB 250316A: Swift ToO observations
  45. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  46. GRB 250314A: EP-FXT afterglow detection
  47. GRB 250314A: Swift/UVOT Upper Limits
  48. GRB 250312B: GRBAlpha detection
  49. GRB 250314A: Swift XRT Detection
  50. GRB 250314A: NOT near-infrared candidate counterpart
  51. GRB 250312B: Fermi GBM Observation
  52. GRB 250313A: Swift-XRT observations
  53. Konus-Wind detection of GRB 250308A
  54. GRB 250313A: Fermi-LAT detection
  55. GRB 250313A: Swift ToO observations
  56. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  57. EP250304a: SVOM/VT optical observation
  58. EP250302a: Chandra X-ray Detection
  59. GRB 250312A: Swift-XRT refined Analysis
  60. GRB 250312A: Enhanced Swift-XRT position
  61. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  62. GRB 250226B: Fermi GBM Observation
  63. Swift GRB 250312A: Global MASTER-Net observations report
  64. GRB 250302A: Fermi GBM Observation
  65. GRB 250312A: Swift detection of a burst
  66. GRB 250223B: Fermi GBM Observation
  67. GRB 250311A: Swift-XRT observations
  68. GRB 250228A: Fermi GBM Observation
  69. GRB 250309B: 1.3m DFOT Optical observations
  70. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  71. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  72. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  73. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  74. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  75. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  76. EP250304a: Chandra detection
  77. GRB 250225B: Swift-BAT refined analysis
  78. GRB 250311A: Tiled Swift observations
  79. IPN triangulation of GRB 250308A (short)
  80. GRB 250309B: Swift-XRT refined Analysis
  81. GRB 250309B / AT2025dws: Swift-UVOT detection
  82. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  83. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  84. GRB 230509B: Tiled Swift observations
  85. GRB 250306A: EIRSAT-1 GMOD detection
  86. Konus-Wind detection of GRB 250306A
  87. GRB 250306A: Swift-BAT refined analysis
  88. GRB 250306A: NuSTAR detection of the prompt emission
  89. GRB 250306A: AstroSat CZTI detection
  90. Swift GRB 250306A: Global MASTER-Net observations report
  91. GRB 250306A: Swift detection of a burst
  92. IPN triangulation of GRB 250222A
  93. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  94. EP250304a: Swift-XRT detection of a fading X-ray source
  95. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  96. EP250302a: Swift/UVOT detection
  97. EP250302a: Swift-XRT observations of a fading X-ray source
  98. EP250228a: Optical observations with Kinder and Swift/UVOT
  99. GRB 250225B: EIRSAT-1 GMOD Detection
  100. GRB 250225B: VLT/HAWKI near-infrared observations

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