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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"

26036 results found.

  1. GRB 250114B: Swift-XRT observations
  2. GRB 250114A: LCO optical counterpart detection.
  3. GRB 250114B: OHP/T193 optical upper limit
  4. GRB 250114A: GRANDMA/TAROT optical afterglow detection
  5. GRB 250114A: Swift-XRT refined Analysis
  6. GRB 250114A: LCOGT optical afterglow i-band detection
  7. GRB 250114B: Swift ToO observations
  8. EP250111a: SAO RAS optical upper limit
  9. GRB 250114A: Enhanced Swift-XRT position
  10. GRB 250114A: VLT/X-shooter spectroscopic redshift z = 4.732
  11. GRB 250114A: REM detection of the optical and NIR counterpart
  12. Swift GRB250114A: Global MASTER-Net OT detection
  13. GRB 250114A: LCO optical observations
  14. GRB 250114A: TRT optical observations
  15. Swift GRB 250114A: Global MASTER-Net observations report
  16. GRB 250114A: Swift detection of a burst with an optical counterpart
  17. GRB 250101A: Terskol Zeiss-2000 optical observations
  18. GRB 250107A: VZLUSAT-2 detection
  19. GRB 250109A / EP250109a: GRBAlpha detection
  20. GRB 250106A: Swift-XRT afterglow detection
  21. EP250111a: KAIT optical observations
  22. GRB 250109A / EP250109a: Mephisto optical upper limits
  23. EP250111a: Swift/XRT detection and fading
  24. EP250108a / AT 2025kg: Swift UVOT detections
  25. EP250109a/GRB 250109A:SVOM/VT optical counterpart
  26. GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
  27. GRB 250109A / EP250109A: Swift/BAT-GUANO localization skymap of a burst
  28. GRB 250109A / EP250109a: Swift detection of the X-ray afterglow
  29. GRB 250108A: Swift/XRT afterglow fading
  30. GRB 250101A: CMO RC-500 optical observations
  31. EP250109a / GRB 250109A: refined EP-WXT analysis and EP-FXT follow-up observation
  32. EP250108a: NOT optical observations
  33. EP250109a: Swift/UVOT non-detection
  34. IPN triangulation of GRB 250107D (short/hard)
  35. IPN triangulation of GRB 250107C
  36. GRB 250108B: Gemini-North likely redshift z = 2.197
  37. GRB 250108B: Swift-BAT refined analysis
  38. GRB 250108B: 1.3m DFOT upper limit
  39. GRB 250108B: REM optical/NIR upper limits
  40. GRB 250101A: Terskol K-800 optical observations
  41. EP250109a: GOTO optical upper limits
  42. EP250109a: Swift/XRT non-detection
  43. GRB 250108A: Swift/UVOT Upper Limits
  44. GRB 250108A: NOT optical upper limit
  45. GRB 250108B: Swift-XRT refined Analysis
  46. Swift GRB 250108B: Global MASTER-Net observations report
  47. GRB 250108B: Gemini-North Candidate Optical Afterglow Detection
  48. GRB 250108A: Swift-XRT afterglow detection
  49. GRB 250108A:SVOM/VT optical candidate
  50. GRB 250108B: Swift/UVOT Upper Limits
  51. GRB 250103A: Swift-XRT afterglow detection
  52. GRB 250108B: Enhanced Swift-XRT position
  53. GRB 250108B: Swift detection of a burst
  54. GRB 250108A: Swift ToO observations
  55. GRB 250107A: Fermi GBM Observation
  56. GRB 241228B: Fermi-LAT detection
  57. GRB 250107A: Swift ToO observations
  58. GRB 250107A: Swift/BAT-GUANO arcminute localization of a burst
  59. GRB 250106A: SVOM/VT 2nd optical deep observation
  60. GRB 250101A: J band upper limit by SYSU 80cm telescope
  61. GRB 250106A: NOT optical observations
  62. GRB 250103B: REM optical/NIR upper limits
  63. GRB 250101A: REM optical/NIR counterpart detection
  64. GRB 250106A: Swift-XRT observations
  65. GRB 250106A: SVOM/VT optical candidate
  66. GRB 250106A: Swift ToO observations
  67. GRB 241229A: SVOM/VT optical upperlimit
  68. GRB 250103B: Swift-XRT refined Analysis
  69. GRB 250103B: LCO/1m optical afterglow candidate detection
  70. GRB 250103B: VLT/X-shooter spectroscopic redshift z = 1.416
  71. GRB 250103A: Swift-XRT observations
  72. GRB 250101A: 1.3m DFOT optical afterglow detection
  73. GRB 241229A: 1.3m DFOT upper limit
  74. GRB 241228A: 1.3m DFOT upper limit
  75. GRB 250103B:SVOM/VT optical counterpart
  76. GRB 250101A: further LCOGT optical afterglow observations
  77. GRB 250103A: NOT optical observations
  78. GRB 250103A: TSHAO optical upper limit
  79. GRB 250103B: LCOGT Optical Upper Limit
  80. Swift GRB 250103B: Global MASTER-Net observations report
  81. GRB 250103A: Swift ToO observations
  82. GRB 250101a: Liverpool Telescope optical follow-up
  83. GRB 250103B: SVOM detection of a long burst
  84. GRB 250103B: Swift detection of a burst
  85. GRB 250101A: NUTTelA-TAO / BSTI Optical Limits
  86. GRB 250103A: SVOM detection of a long burst (duplicate submission)
  87. GRB 250103A: SVOM detection of a long burst
  88. LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO
  89. GRB 250101A: Swift-BAT refined analysis
  90. GRB 250101A: further SAO RAS optical observations
  91. GRB 250101A: LCO optical counterpart detection
  92. GRB 250101A NUTTelA-TAO / BSTI Early Measurements
  93. GRB 250101A: GMG spectroscopic redshift at z ~ 2.481
  94. GRB 250101A: Swift/UVOT Detection
  95. GRB 250101A: 1.6m Mephisto multi-band optical followup
  96. GRB 250101A: Swift-XRT refined Analysis
  97. GRB 250101A: Montarrenti Observatory optical observations and rebrightening
  98. GRB 250101A: LCOGT optical afterglow detection
  99. GRB 250101A: OASDG optical observations
  100. GRB 250101A: SAO RAS observations of optical brightening

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