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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"

19592 results found.

  1. GRB 250321A: GOTO optical upper limits
  2. GRB 250321A: Swift-XRT localisation
  3. GRB 250321A: Fermi GBM Observation
  4. GRB 250321A: Swift detection of a burst
  5. GRB250312A: Swift/UVOT Upper Limits
  6. GRB 250317B: Swift-XRT observations
  7. GRB 250316A: Swift/UVOT Upper Limits
  8. GRB 250314A: REM optical/NIR upper limits
  9. GRB 250316A: AbAO AS-32 Optical Upper Limit
  10. GRB 250316A: Swift-XRT afterglow detection
  11. GRB 250316A: Fermi GBM Observation
  12. GRB 250316A: Swift-XRT observations
  13. GRB 250316A: Swift ToO observations
  14. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  15. GRB 250314A: EP-FXT afterglow detection
  16. GRB 250314A: Swift/UVOT Upper Limits
  17. GRB 250312B: GRBAlpha detection
  18. GRB 250314A: Swift XRT Detection
  19. GRB 250314A: NOT near-infrared candidate counterpart
  20. GRB 250312B: Fermi GBM Observation
  21. GRB 250313A: Swift-XRT observations
  22. Konus-Wind detection of GRB 250308A
  23. GRB 250313A: Fermi-LAT detection
  24. GRB 250313A: Swift ToO observations
  25. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  26. EP250304a: SVOM/VT optical observation
  27. EP250302a: Chandra X-ray Detection
  28. GRB 250312A: Swift-XRT refined Analysis
  29. GRB 250312A: Enhanced Swift-XRT position
  30. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  31. GRB 250226B: Fermi GBM Observation
  32. Swift GRB 250312A: Global MASTER-Net observations report
  33. GRB 250302A: Fermi GBM Observation
  34. GRB 250312A: Swift detection of a burst
  35. GRB 250223B: Fermi GBM Observation
  36. GRB 250311A: Swift-XRT observations
  37. GRB 250228A: Fermi GBM Observation
  38. GRB 250309B: 1.3m DFOT Optical observations
  39. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  40. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  41. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  42. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  43. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  44. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  45. EP250304a: Chandra detection
  46. GRB 250225B: Swift-BAT refined analysis
  47. GRB 250311A: Tiled Swift observations
  48. IPN triangulation of GRB 250308A (short)
  49. GRB 250309B: Swift-XRT refined Analysis
  50. GRB 250309B / AT2025dws: Swift-UVOT detection
  51. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  52. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  53. GRB 230509B: Tiled Swift observations
  54. GRB 250306A: EIRSAT-1 GMOD detection
  55. Konus-Wind detection of GRB 250306A
  56. GRB 250306A: Swift-BAT refined analysis
  57. GRB 250306A: NuSTAR detection of the prompt emission
  58. GRB 250306A: AstroSat CZTI detection
  59. Swift GRB 250306A: Global MASTER-Net observations report
  60. GRB 250306A: Swift detection of a burst
  61. IPN triangulation of GRB 250222A
  62. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  63. EP250304a: Swift-XRT detection of a fading X-ray source
  64. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  65. EP250302a: Swift/UVOT detection
  66. EP250302a: Swift-XRT observations of a fading X-ray source
  67. EP250228a: Optical observations with Kinder and Swift/UVOT
  68. GRB 250225B: EIRSAT-1 GMOD Detection
  69. GRB 250225B: VLT/HAWKI near-infrared observations
  70. EP250228a: updates on the EP observations
  71. EP250228a: Swift/XRT localisation
  72. GRB 250225B: INTEGRAL SPI-ACS detection
  73. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  74. GRB 250225B: Fermi GBM Observation
  75. GRB 250221A: ATCA Detections and Upper Limits
  76. GRB 250225B: REM NIR upper limits
  77. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  78. Konus-Wind detection of GRB 250225B
  79. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  80. GRB 250225B: VLT/FORS2 candidate optical afterglow
  81. GRB 250225B: SVOM/GRM observation of a long burst
  82. GRB 250221A: EP-FXT detection of the X-ray afterglow
  83. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  84. Swift GRB 250225B: Global MASTER-Net observations report
  85. GRB 250225B: Swift detection of a burst
  86. GRB 250221A: Swift-BAT refined analysis
  87. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  88. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  89. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  90. GRB 250207a: ATCA Radio Upper Limits
  91. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  92. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  93. GRB 250119B: VZLUSAT-2 detection
  94. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  95. GRB 250219A: EP-FXT afterglow detection
  96. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  97. EP250223a: REM NIR upper limit
  98. EP250223a: TRT optical afterglow observation
  99. EP250223a: refined analysis of the EP-WXT and FXT observations
  100. EP250223a: SVOM/VT optical observation

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