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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"

28076 results found.

  1. EP250508a: follow-up observation with EP-FXT
  2. EP250508a: KAIT optical upper limit
  3. GRB 250507A: KAIT optical upper limit
  4. GRB 250506A: GECAM detection
  5. GRB 250506A: Swift-XRT afterglow detection
  6. GRB 250506A: SVOM/VT optical upper limit
  7. EP250508a: Einstein Probe detection of an X-ray transient
  8. GRB 250507A: Swift-XRT refined Analysis
  9. GRB 250506A: Swift/UVOT Upper Limits
  10. GRB 250427B : SVOM detection of a burst through offline search
  11. GRB 250430A / EP250430a: AstroSat CZTI detection
  12. EP#01709175213/IGR J19566+0326: Swift-XRT detection
  13. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  14. GRB 250506A: Swift-XRT observations
  15. EP-WXT trigger 01709175213: a new X-ray outburst of LMXB MAXI J1957+032
  16. GRB 250507A: SVOM detection of a long burst
  17. GRB 250504A: EIRSAT-1 GMOD Detection
  18. GRB 250506A: Swift ToO observations
  19. IceCube-250506A - IceCube observation of a high-energy neutrino candidate track-like event
  20. GRB 250430A: Konus-Wind detection and joint Konus-Wind+Swift-BAT spectral analysis
  21. GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
  22. GRB 250506A: Swift XRT observations and possible counterpart detection
  23. GRB 250506A: TRT optical observations
  24. GRB 250506A: SVOM detection of a burst
  25. GRB 250506A: Fermi GBM Final Real-time Localization
  26. GRB 250504A: Swift-XRT refined Analysis
  27. GRB 250504A: VLT/X-shooter upper limits
  28. GRB 250504A: SVOM/VT upper limit
  29. GRB 250504A: REM optical/NIR observations
  30. GRB 250502A: REM optical/NIR observations
  31. GRB 250505A: Fermi GBM Final Real-time Localization
  32. GRB 250504A: MeerLICHT optical afterglow detection
  33. GRB 250504A: Enhanced Swift-XRT position
  34. GRB 250504A: Swift detection of a burst
  35. GRB 250504A: Fermi GBM Final Real-time Localization
  36. GRB 250502A: Mondy and Tien-Shan Optical Observations
  37. GRB 250502A: KAIT optical observations
  38. GRB 250502A: Montarrenti Observatory optical detection
  39. GRB 250502A: Swift-XRT afterglow detection
  40. GRB 250502a: Liverpool Telescope optical follow-up
  41. GRB 250502B: AstroSat CZTI detection
  42. GRB 250502A: AKO Optical Afterglow Detection
  43. GRB 250502A: LCO optical counterpart detection
  44. GRB 250502A: Swift ToO observations
  45. GRB 250502A: Redshift from OSIRIS+/GTC z = 2.163
  46. GRB 250502C: Fermi GBM Final Localization
  47. GRB 250407A: VZLUSAT-2 detection
  48. GRB 250430A: Swift-XRT refined Analysis
  49. GRB 250502A: Early optical counterpart detection by LCO.
  50. GRB 250430A: Swift/UVOT Detection
  51. GRB 250502A: TRT optical afterglow confirmation
  52. GRB 250430A: Enhanced Swift-XRT position
  53. GRB 250430A: Optical Observations via Virtual Telescope Project, Italy
  54. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  55. GRB 250502B: Fermi GBM Final Real-time Localization
  56. GRB 250502A: SVOM detection of a burst
  57. GRB 250430A: SVOM/VT optical observations
  58. GRB 250430A: KAIT optical observations
  59. EP250428b: Pan-STARRS follow-up, upper limit on the optical counterpart, and possible host galaxy.
  60. GRB 250430A: NUTTelA-TAO Early Measurements
  61. EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
  62. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  63. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  64. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  65. GRB 250430A: AKO Optical Afterglow Detection
  66. EP 250427A: Optical counterpart detection by LCO.
  67. GRB 250430A: Swift detection of a burst with optical counterpart
  68. EP250427a / GRB 250427A: OHP/T193 continued photometric observations
  69. SVOM/sb25043004: SVOM detection of a X-ray transient
  70. EP250428b: refined analysis of the EP-FXT follow-up observation
  71. IceCube-250429A - IceCube observation of a high-energy neutrino candidate track-like event
  72. GRB 250427A: Swift/UVOT Detection
  73. EP250428b: Einstein Probe detection of a fast X-ray transient
  74. EP250427a / GRB 250427A: OHP/T193 photometric observations
  75. EP250427a: EP-FXT follow-up observations
  76. EP250427a: Lesedi optical counterpart detection
  77. GRB250427A/EP250427a GIT optical afterglow detection:
  78. EP250427a: LT optical counterpart detection
  79. GRB 250427A: Swift-XRT refined Analysis
  80. EP250427a / GRB 250427A: LCO optical counterpart detection
  81. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  82. EP250427A/GRB250427A: Keck/LRIS redshift
  83. EP250427a: REM optical/NIR afterglow detection
  84. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  85. EP250427A: COLIBRÍ Optical Detection
  86. EP250427a: TRT optical counterpart detection
  87. EP 250427a: BOOTES-7 optical afterglow candidate
  88. EP250427a: Einstein Probe detection of a fast X-ray transient
  89. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event
  90. GRB 250424A: PRIME near-infrared detection
  91. GRB 250424A: WINTER J-band detection
  92. GRB 250424A: EIRSAT-1 GMOD Detection
  93. GRB 250424A: Swift/UVOT Detection
  94. Konus-Wind detection of GRB 250424A
  95. GRB 250424A: Skynet Optical Observations
  96. GRB 250424A: Kilonova-Catcher optical afterglow detection
  97. GRB 250419a: Continued Liverpool Telescope observations
  98. GRB 250419A: Liverpool Telescope optical upper limit
  99. GRB 250407A: GRBAlpha detection
  100. GRB 250404A / EP250404a: GRBAlpha detection

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