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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"

19941 results found.

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

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