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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"

19610 results found.

  1. GRB 250322A: NOT optical upper limits
  2. GRB 250322A: Enhanced Swift-XRT position
  3. GRB 250322A: MASTER optical observation
  4. GRB 250322A: Swift detection of a short burst
  5. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  6. GRB 250225B: GECAM-A detection
  7. GRB 250312A: GECAM-A detection
  8. GRB 250321B: Swift ToO observations
  9. GRB 250321A: Swift-BAT refined analysis
  10. GRB 250321A: Swift-XRT refined Analysis
  11. GRB 250320B: Fermi-LAT detection
  12. GRB 250321A: Swift/UVOT Upper Limits
  13. EP250321a: LCO optical counterpart detection
  14. EP250321a: Swift-XRT detection of an X-ray source
  15. Swift GRB 250321A: Global MASTER-Net observations report
  16. GRB 250321A: GOTO optical upper limits
  17. GRB 250321A: Swift-XRT localisation
  18. GRB 250321A: Fermi GBM Observation
  19. GRB 250321A: Swift detection of a burst
  20. GRB250312A: Swift/UVOT Upper Limits
  21. GRB 250317B: Swift-XRT observations
  22. GRB 250316A: Swift/UVOT Upper Limits
  23. GRB 250314A: REM optical/NIR upper limits
  24. GRB 250316A: AbAO AS-32 Optical Upper Limit
  25. GRB 250316A: Swift-XRT afterglow detection
  26. GRB 250316A: Fermi GBM Observation
  27. GRB 250316A: Swift-XRT observations
  28. GRB 250316A: Swift ToO observations
  29. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  30. GRB 250314A: EP-FXT afterglow detection
  31. GRB 250314A: Swift/UVOT Upper Limits
  32. GRB 250312B: GRBAlpha detection
  33. GRB 250314A: Swift XRT Detection
  34. GRB 250314A: NOT near-infrared candidate counterpart
  35. GRB 250312B: Fermi GBM Observation
  36. GRB 250313A: Swift-XRT observations
  37. Konus-Wind detection of GRB 250308A
  38. GRB 250313A: Fermi-LAT detection
  39. GRB 250313A: Swift ToO observations
  40. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  41. EP250304a: SVOM/VT optical observation
  42. EP250302a: Chandra X-ray Detection
  43. GRB 250312A: Swift-XRT refined Analysis
  44. GRB 250312A: Enhanced Swift-XRT position
  45. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  46. GRB 250226B: Fermi GBM Observation
  47. Swift GRB 250312A: Global MASTER-Net observations report
  48. GRB 250302A: Fermi GBM Observation
  49. GRB 250312A: Swift detection of a burst
  50. GRB 250223B: Fermi GBM Observation
  51. GRB 250311A: Swift-XRT observations
  52. GRB 250228A: Fermi GBM Observation
  53. GRB 250309B: 1.3m DFOT Optical observations
  54. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  55. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  56. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  57. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  58. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  59. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  60. EP250304a: Chandra detection
  61. GRB 250225B: Swift-BAT refined analysis
  62. GRB 250311A: Tiled Swift observations
  63. IPN triangulation of GRB 250308A (short)
  64. GRB 250309B: Swift-XRT refined Analysis
  65. GRB 250309B / AT2025dws: Swift-UVOT detection
  66. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  67. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  68. GRB 230509B: Tiled Swift observations
  69. GRB 250306A: EIRSAT-1 GMOD detection
  70. Konus-Wind detection of GRB 250306A
  71. GRB 250306A: Swift-BAT refined analysis
  72. GRB 250306A: NuSTAR detection of the prompt emission
  73. GRB 250306A: AstroSat CZTI detection
  74. Swift GRB 250306A: Global MASTER-Net observations report
  75. GRB 250306A: Swift detection of a burst
  76. IPN triangulation of GRB 250222A
  77. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  78. EP250304a: Swift-XRT detection of a fading X-ray source
  79. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  80. EP250302a: Swift/UVOT detection
  81. EP250302a: Swift-XRT observations of a fading X-ray source
  82. EP250228a: Optical observations with Kinder and Swift/UVOT
  83. GRB 250225B: EIRSAT-1 GMOD Detection
  84. GRB 250225B: VLT/HAWKI near-infrared observations
  85. EP250228a: updates on the EP observations
  86. EP250228a: Swift/XRT localisation
  87. GRB 250225B: INTEGRAL SPI-ACS detection
  88. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  89. GRB 250225B: Fermi GBM Observation
  90. GRB 250221A: ATCA Detections and Upper Limits
  91. GRB 250225B: REM NIR upper limits
  92. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  93. Konus-Wind detection of GRB 250225B
  94. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  95. GRB 250225B: VLT/FORS2 candidate optical afterglow
  96. GRB 250225B: SVOM/GRM observation of a long burst
  97. GRB 250221A: EP-FXT detection of the X-ray afterglow
  98. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  99. Swift GRB 250225B: Global MASTER-Net observations report
  100. GRB 250225B: Swift detection of a burst

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