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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"

21466 results found.

  1. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  2. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  3. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  4. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  5. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  6. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  7. EP250304a: Chandra detection
  8. GRB 250225B: Swift-BAT refined analysis
  9. GRB 250311A: Tiled Swift observations
  10. IPN triangulation of GRB 250308A (short)
  11. GRB 250309B: Swift-XRT refined Analysis
  12. GRB 250309B / AT2025dws: SAO RAS optical observations
  13. GRB 250309B / AT2025dws: Swift-UVOT detection
  14. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  15. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  16. GRB 230509B: Tiled Swift observations
  17. GRB 250306A: EIRSAT-1 GMOD detection
  18. Konus-Wind detection of GRB 250306A
  19. GRB 250306A: Swift-BAT refined analysis
  20. GRB 250306A: NuSTAR detection of the prompt emission
  21. GRB 250306A: AstroSat CZTI detection
  22. Swift GRB 250306A: Global MASTER-Net observations report
  23. GRB 250306A: Swift detection of a burst
  24. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  25. IPN triangulation of GRB 250222A
  26. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  27. EP250304a: Swift-XRT detection of a fading X-ray source
  28. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  29. EP250302a: Swift/UVOT detection
  30. EP250302a: NUTTelA-TAO Early Measurments
  31. EP250302a: Xinglong F60B optical observation
  32. EP250302a: Swift-XRT observations of a fading X-ray source
  33. EP250228a: Optical observations with Kinder and Swift/UVOT
  34. GRB 250225B: EIRSAT-1 GMOD Detection
  35. GRB 250225B: VLT/HAWKI near-infrared observations
  36. EP250228a: updates on the EP observations
  37. EP250228a: Swift/XRT localisation
  38. GRB 250225B: INTEGRAL SPI-ACS detection
  39. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  40. GRB 250225B: Fermi GBM Observation
  41. GRB 250221A: ATCA Detections and Upper Limits
  42. GRB 250225B: REM NIR upper limits
  43. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  44. Konus-Wind detection of GRB 250225B
  45. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  46. GRB 250225B: VLT/FORS2 candidate optical afterglow
  47. GRB 250225B: SVOM/GRM observation of a long burst
  48. GRB 250221A: EP-FXT detection of the X-ray afterglow
  49. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  50. Swift GRB 250225B: Global MASTER-Net observations report
  51. GRB 250225B: Swift detection of a burst
  52. GRB 250221A: Swift-BAT refined analysis
  53. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  54. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  55. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  56. GRB 250207a: ATCA Radio Upper Limits
  57. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  58. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  59. GRB 250119B: VZLUSAT-2 detection
  60. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  61. GRB 250219A: EP-FXT afterglow detection
  62. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  63. EP250223a: REM NIR upper limit
  64. EP250223a: TRT optical afterglow observation
  65. EP250223a: refined analysis of the EP-WXT and FXT observations
  66. EP250223a: SVOM/VT optical observation
  67. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  68. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO trigger with ID 762004910: Identification of a GW compact binary merger candidate possibly associated with a sub-threshold Swift/BAT-GUANO trigger
  69. EP250223a: OASDG optical observations
  70. EP250223a: LCO detection of the afterglow
  71. EP250223a: early optical detection by BOOTES-4
  72. EP250223a: NOT redshift z = 2.756
  73. EP250223a: Swift/XRT localization
  74. GRB 250221A: VLA radio detection
  75. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  76. GRB 250221A: continued Mondy optical observations, brightening afterglow
  77. GRB 250221A: Optical counterpart detection by LCO.
  78. GRB 250221A: Mondy optical observations
  79. Konus-Wind detection of GRB 250221A
  80. GRB 250221A: Assy optical observations
  81. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  82. GRB 250221A: GRANDMA/TAROT Detection
  83. GRB 250221A: Swift-XRT refined Analysis
  84. GRB 250221A: NOT optical observations
  85. GRB 250221A: 1.6m Mephisto optical detection
  86. GRB 250221A: AKO Optical Upper Limit
  87. GRB 250221A: Swift/UVOT Detection
  88. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  89. GRB 250221A: REM optical/NIR afterglow detection
  90. GRB 250221A: Enhanced Swift-XRT position
  91. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  92. GRB 250221A: Swift detection of a burst with an optical counterpart
  93. Swift GRB250221.15: Global MASTER-Net OT detection
  94. Swift GRB250221.15: Global MASTER-Net observations report
  95. GRB 250219A: Swift/UVOT Upper Limits
  96. GRB 250219A: OHP/T193 optical upper limit
  97. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  98. GRB 250219A: 1.6m Mephisto optical upper limits
  99. GRB 250219A: SVOM/VT optical counterpart
  100. GRB 250219A: Swift-XRT observations

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