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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"

23572 results found.

  1. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  2. GRB 250507A: refined SVOM/MXT data analysis
  3. GRB 250507A: REM optical/NIR observations
  4. GRB 250506A: Swift-XRT observations
  5. GRB 250507A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  6. EP-WXT trigger 01709175213: a new X-ray outburst of LMXB MAXI J1957+032
  7. GRB 250506A: Mephisto optical upper limits
  8. GRB 250430A: Konus-Wind detection and joint Konus-Wind+Swift-BAT spectral analysis
  9. GRB 250506A: Xinglong 2.16m optical upper limit
  10. GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
  11. GRB 250506A: REM optical/NIR upper limits
  12. GRB 250506A: TRT optical observations
  13. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
  14. GRB 250504A: Swift-BAT refined analysis
  15. GRB 250430A: Swift-BAT refined analysis
  16. GRB 250506A: Fermi GBM Final Real-time Localization
  17. GRB 250504A: Swift-XRT refined Analysis
  18. GRB 250504A: VLT/X-shooter upper limits
  19. GRB 250504A: REM optical/NIR observations
  20. GRB 250502A: REM optical/NIR observations
  21. GRB 250504A: MeerLICHT optical afterglow detection
  22. GRB 250504A: Fermi GBM Observation
  23. Fermi GRB 250504A: Global MASTER-Net observations report
  24. GRB 250504A: Swift detection of a burst
  25. GRB 250502A: KAIT optical observations
  26. GRB 250502A: Montarrenti Observatory optical detection
  27. GRB 250502B: AstroSat CZTI detection
  28. GRB 250502A: LCO optical counterpart detection
  29. GRB 250502A: Redshift from OSIRIS+/GTC z = 2.163
  30. GRB 250407A: VZLUSAT-2 detection
  31. GRB 250502B: DDOTI Optical Observations
  32. GRB 250430A: Swift-XRT refined Analysis
  33. GRB 250502A: Early optical counterpart detection by LCO.
  34. GRB 250430A: Swift/UVOT Detection
  35. GRB 250502A: TRT optical afterglow confirmation
  36. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  37. GRB 250502A: SVOM detection of a burst
  38. GRB 250430A: KAIT optical observations
  39. EP250428b: Pan-STARRS follow-up, upper limit on the optical counterpart, and possible host galaxy.
  40. GRB 250430A / EP250430a: J-band upper limits with WINTER
  41. GRB 250430A: NUTTelA-TAO Early Measurements
  42. GRB 250430A: DDOTI Optical Observations
  43. GRB 250430A: Leavitt Observatory optical upper limit
  44. GRB 250430A : MITSuME Akeno optical upper limits
  45. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  46. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  47. GRB 250430A: Kanata optical upper limit
  48. EP 250427A: Optical counterpart detection by LCO.
  49. GRB 250430A: Swift detection of a burst with optical counterpart
  50. EP250428b: refined analysis of the EP-FXT follow-up observation
  51. EP250428b: SVOM/VT upper limit
  52. EP250428b: SAO RAS optical upper limit
  53. EP250428b: LAST optical upper limit
  54. GRB 250427A: Swift/UVOT Detection
  55. EP250428b: Einstein Probe detection of a fast X-ray transient
  56. EP250427a: Lesedi optical counterpart detection
  57. EP250427A: COLIBRÍ Continuing Optical Observations
  58. GRB 250427A: Swift-XRT refined Analysis
  59. EP250427a / GRB 250427A: LCO optical counterpart detection
  60. EP250427a: REM optical/NIR afterglow detection
  61. GRB 250424A: LCO optical observation
  62. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  63. EP250427A: COLIBRÍ Optical Detection
  64. EP250427a: TRT optical counterpart detection
  65. EP 250427a: BOOTES-7 optical afterglow candidate
  66. GRB 250424A: Swift-BAT refined analysis
  67. GRB 250424A: PRIME near-infrared detection
  68. GRB 250424A: WINTER J-band detection
  69. Konus-Wind detection of GRB 250424A
  70. GRB 250424A: Kilonova-Catcher optical afterglow detection
  71. GRB 250407A: GRBAlpha detection
  72. GRB 250404A / EP250404a: GRBAlpha detection
  73. GRB 250330B: GRBAlpha detection
  74. GRB 250419A: SVOM/ECLAIRs refined analysis
  75. GRB 250424A: Swift-XRT refined Analysis
  76. GRB 250424A: AstroSat CZTI detection of a bright long burst
  77. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  78. GRB 250424A: DDOTI Afterglow Detection
  79. GRB 250424A: REM optical/NIR afterglow detection
  80. GRB 250424A: Swift detection of a burst with an optical counterpart
  81. EP250421a: Nickel optical upper limit
  82. EP250421a: Upper limits from Fermi-GBM Observations
  83. SVOM/sb25042207: BOOTES-2 early optical upper limit
  84. SVOM/sb25042207: GOTO optical upper limits
  85. GRB 250421A: AstroSat CZTI detection
  86. IceCube-250421A: DDOTI Detection of the LAST Candidate
  87. GRB 250419A: Mephisto Multi-band Optical Detection
  88. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  89. EP250421a: REM optical upper limit
  90. EP250421a: Swift/XRT counterpart detection
  91. EP250421A: COLIBRÍ Optical Upper Limit
  92. GRB 250421B: AstroSat CZTI detection of a bright long burst
  93. EP250421a: Mephisto optical counterpart confirmation
  94. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  95. GRB 250419A: LCO optical observation
  96. GRB 250419A: LCO optical afterglow multi-band observations
  97. GRB 250407A: rest-frame energetics from Konus-Wind observation
  98. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  99. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  100. GRB 250419A: Swift-XRT refined Analysis

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