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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"

18632 results found.

  1. IPN triangulation of GRB 250222A
  2. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  3. EP250304a: Swift-XRT detection of a fading X-ray source
  4. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  5. EP250302a: Swift/UVOT detection
  6. EP250302a: Swift-XRT observations of a fading X-ray source
  7. EP250228a: Optical observations with Kinder and Swift/UVOT
  8. GRB 250225B: EIRSAT-1 GMOD Detection
  9. GRB 250225B: VLT/HAWKI near-infrared observations
  10. EP250228a: updates on the EP observations
  11. EP250228a: Swift/XRT localisation
  12. GRB 250225B: INTEGRAL SPI-ACS detection
  13. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  14. GRB 250225B: Fermi GBM Observation
  15. GRB 250221A: ATCA Detections and Upper Limits
  16. GRB 250225B: REM NIR upper limits
  17. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  18. Konus-Wind detection of GRB 250225B
  19. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  20. GRB 250225B: VLT/FORS2 candidate optical afterglow
  21. GRB 250225B: SVOM/GRM observation of a long burst
  22. GRB 250221A: EP-FXT detection of the X-ray afterglow
  23. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  24. Swift GRB 250225B: Global MASTER-Net observations report
  25. GRB 250225B: Swift detection of a burst
  26. GRB 250221A: Swift-BAT refined analysis
  27. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  28. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  29. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  30. GRB 250207a: ATCA Radio Upper Limits
  31. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  32. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  33. GRB 250119B: VZLUSAT-2 detection
  34. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  35. GRB 250219A: EP-FXT afterglow detection
  36. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  37. EP250223a: REM NIR upper limit
  38. EP250223a: TRT optical afterglow observation
  39. EP250223a: refined analysis of the EP-WXT and FXT observations
  40. EP250223a: SVOM/VT optical observation
  41. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  42. 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
  43. EP250223a: OASDG optical observations
  44. EP250223a: LCO detection of the afterglow
  45. EP250223a: early optical detection by BOOTES-4
  46. EP250223a: NOT redshift z = 2.756
  47. EP250223a: Swift/XRT localization
  48. GRB 250221A: VLA radio detection
  49. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  50. GRB 250221A: continued Mondy optical observations, brightening afterglow
  51. GRB 250221A: Optical counterpart detection by LCO.
  52. GRB 250221A: Mondy optical observations
  53. Konus-Wind detection of GRB 250221A
  54. GRB 250221A: Assy optical observations
  55. GRB 250221A: GRANDMA/TAROT Detection
  56. GRB 250221A: Swift-XRT refined Analysis
  57. GRB 250221A: NOT optical observations
  58. GRB 250221A: 1.6m Mephisto optical detection
  59. GRB 250221A: AKO Optical Upper Limit
  60. GRB 250221A: Swift/UVOT Detection
  61. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  62. GRB 250221A: REM optical/NIR afterglow detection
  63. GRB 250221A: Enhanced Swift-XRT position
  64. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  65. GRB 250221A: Swift detection of a burst with an optical counterpart
  66. Swift GRB250221.15: Global MASTER-Net OT detection
  67. Swift GRB250221.15: Global MASTER-Net observations report
  68. GRB 250219A: Swift/UVOT Upper Limits
  69. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  70. GRB 250219A: 1.6m Mephisto optical upper limits
  71. GRB 250219A: SVOM/VT optical counterpart
  72. GRB 250219A: Swift-XRT observations
  73. GRB 250219A: Swift ToO observations
  74. GRB 250217C: Swift-XRT observations
  75. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  76. GRB 250217C: Tiled Swift observations
  77. IPN triangulation of GRB 250217C (short)
  78. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  79. SVOM/sb25021804: SVOM detection of a long X-ray transient
  80. GRB 250213A: Swift-XRT observations
  81. GRB 250215A / EP250215a: LCO detection of the afterglow
  82. GRB 250215A: Swift/UVOT Upper Limits
  83. GRB 250215A: Fermi GBM Observation
  84. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  85. GRB 250215A: Swift-XRT refined Analysis
  86. GRB 250213A: Swift ToO observations
  87. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  88. GRB 250211A: Swift ToO observations
  89. GRB 250207A: Fermi GBM Observation
  90. Konus-Wind detection of GRB 250207A
  91. GRB 250207A: Skynet optical afterglow observations
  92. GRB 250207A: 1.3m DFOT Optical observations
  93. GRB 250206A: Swift-XRT observations
  94. GRB 250129A: GRANDMA Continued Afterglow Detection
  95. GRB 250207A: Swift-BAT refined analysis
  96. GRB 250205A: 1.3m DFOT optical upper limit
  97. GRB 250206A: Tiled Swift observations
  98. GRB 250206A: Fermi-LAT detection
  99. GRB 250207B: Swift-XRT observations
  100. EP250207a: EP-WXT detection and XRT follow-up observation

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