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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"

26050 results found.

  1. Konus-Wind detection of GRB 250225B
  2. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  3. GRB 250225B: VLT optical and near-infrared candidate counterpart
  4. GRB 250225B: VLT/FORS2 candidate optical afterglow
  5. GRB 250225B: SVOM/GRM observation of a long burst
  6. GRB 250221A: EP-FXT detection of the X-ray afterglow
  7. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  8. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  9. Swift GRB 250225B: Global MASTER-Net observations report
  10. GRB 250225B: Swift detection of a burst
  11. EP250223a: GROWTH-India Telescope optical observations
  12. GRB 250221A: Swift-BAT refined analysis
  13. EP250215A: J band upper limit by SYSU 80cm telescope
  14. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  15. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  16. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  17. GRB 250207a: ATCA Radio Upper Limits
  18. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  19. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  20. GRB 250119B: VZLUSAT-2 detection
  21. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  22. GRB 250219A: EP-FXT afterglow detection
  23. EP250223a: GOTO optical afterglow detections
  24. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  25. EP250223a: REM NIR upper limit
  26. EP250223a: TRT optical afterglow observation
  27. EP250223a: refined analysis of the EP-WXT and FXT observations
  28. EP250223a: 1.6m Mephisto and 50cm array observations
  29. GRB 250221A: TNOT detection of the optical counterpart
  30. EP250223a: SVOM/VT optical observation
  31. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  32. 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
  33. EP250223a: OASDG optical observations
  34. EP250223a: LCO detection of the afterglow
  35. EP250223a: early optical detection by BOOTES-4
  36. EP250223a: NOT redshift z = 2.756
  37. EP250223a: Swift/XRT localization
  38. EP250223a: NOT optical afterglow candidate
  39. GRB 250221A: VLA radio detection
  40. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  41. GRB 250221A: continued Mondy optical observations, brightening afterglow
  42. GRB 250221A: Optical counterpart detection by LCO.
  43. GRB 250221A: Mondy optical observations
  44. Konus-Wind detection of GRB 250221A
  45. GRB 250221A: Assy optical observations
  46. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  47. GRB 250221A: VLT/X-shooter redshift z = 0.768
  48. GRB 250221A: GRANDMA/TAROT Detection
  49. GRB 250221A: Swift-XRT refined Analysis
  50. GRB 250221A: NOT optical observations
  51. GRB 250221A: 1.6m Mephisto optical detection
  52. GRB 250221A: AKO Optical Upper Limit
  53. GRB 250221A: Swift/UVOT Detection
  54. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  55. GRB 250221A: REM optical/NIR afterglow detection
  56. GRB 250221A: Enhanced Swift-XRT position
  57. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  58. GRB 250221A: Swift detection of a burst with an optical counterpart
  59. Swift GRB250221.15: Global MASTER-Net OT detection
  60. Swift GRB250221.15: Global MASTER-Net observations report
  61. GRB 250219A: Swift/UVOT Upper Limits
  62. GRB 250219A: OHP/T193 optical upper limit
  63. GRB 250219A: NOT optical observations
  64. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  65. GRB 250219A: 1.6m Mephisto optical upper limits
  66. GRB 250219A: SVOM/VT optical counterpart
  67. GRB 250219A: Swift-XRT observations
  68. GRB 250219A: Swift ToO observations
  69. GRB 250217C: Swift-XRT observations
  70. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  71. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  72. GRB 250217C: Tiled Swift observations
  73. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  74. IPN triangulation of GRB 250217C (short)
  75. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  76. SVOM/sb25021804: SVOM detection of a long X-ray transient
  77. GRB 250213A: Swift-XRT observations
  78. GRB 250215A / EP250215a: LCO detection of the afterglow
  79. GRB 250215A: Swift/UVOT Upper Limits
  80. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  81. EP250215a / GRB 250215A : GTC redshift z = 4.61
  82. GRB 250215A: Fermi GBM Observation
  83. EP250215a / GRB 250215A : NOT optical observations
  84. GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
  85. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  86. GRB 250215A: Swift-XRT refined Analysis
  87. GRB 250213A: Swift ToO observations
  88. GRB 250205A: VIRT Optical Upper Limit
  89. EP250207B: Chandra localization of the X-ray counterpart
  90. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  91. GRB 250211A: Swift ToO observations
  92. GRB 250207A: Fermi GBM Observation
  93. Konus-Wind detection of GRB 250207A
  94. GRB 250207A: Skynet optical afterglow observations
  95. GRB 241128A: VIRT Optical Upper Limit
  96. GRB 250207A: 1.3m DFOT Optical observations
  97. GRB 250206A: Swift-XRT observations
  98. GRB 250129A: GRANDMA Continued Afterglow Detection
  99. GRB 250207A: Swift-BAT refined analysis
  100. GRB 250205A: 1.3m DFOT optical upper limit

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