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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"

18631 results found.

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

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