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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

37993 results found.

  1. GRB 250502C: Fermi GBM Final Localization
  2. GRB 250407A: VZLUSAT-2 detection
  3. GRB 250502B: DDOTI Optical Observations
  4. GRB 250430A: Swift-XRT refined Analysis
  5. GRB 250502A: Early optical counterpart detection by LCO.
  6. GRB 250430A: Swift/UVOT Detection
  7. GRB 250502A: SVOM/VT optical bump
  8. GRB 250502A: TRT optical afterglow confirmation
  9. GRB 250430A: Enhanced Swift-XRT position
  10. Fermi GRB 250502B: Global MASTER-Net observations report
  11. GRB 250430A: Optical Observations via Virtual Telescope Project, Italy
  12. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  13. GRB 250502B: Fermi GBM Final Real-time Localization
  14. GRB 250502A: SVOM detection of a burst
  15. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  16. GRB 250430A: SVOM/VT optical observations
  17. GRB 250430A: KAIT optical observations
  18. GRB 250430A / EP250430a: J-band upper limits with WINTER
  19. GRB 250430A: NUTTelA-TAO Early Measurements
  20. EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
  21. GRB 250430A: DDOTI Optical Observations
  22. GRB 250430A: Leavitt Observatory optical upper limit
  23. GRB 250430A: Bassano Bresciano Observatory upper limit
  24. GRB 250430A : MITSuME Akeno optical upper limits
  25. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  26. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  27. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  28. GRB 250430A: AKO Optical Afterglow Detection
  29. GRB 250430A: Kanata optical upper limit
  30. EP 250427A: Optical counterpart detection by LCO.
  31. GRB 250430A: Swift detection of a burst with optical counterpart
  32. Swift GRB250430.73: Global MASTER-Net observations report
  33. EP250427a / GRB 250427A: OHP/T193 continued photometric observations
  34. EP250428b: SAO RAS optical upper limit
  35. GRB 250427A: Swift/UVOT Detection
  36. EP250427a / GRB 250427A: OHP/T193 photometric observations
  37. EP250427a: EP-FXT follow-up observations
  38. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  39. GRB250427A/EP250427a GIT optical afterglow detection:
  40. GRB 250427A: Swift-XRT refined Analysis
  41. EP250427a / GRB 250427A: LCO optical counterpart detection
  42. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  43. EP250427A/GRB250427A: Keck/LRIS redshift
  44. GRB 250424A: LCO optical observation
  45. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  46. GRB 250424A: Swift-BAT refined analysis
  47. GRB 250424A: SVOM/GRM observation of a long burst
  48. GRB 250424A: PRIME near-infrared detection
  49. GRB 250424A: WINTER J-band detection
  50. GRB 250424A: EIRSAT-1 GMOD Detection
  51. GRB 250424A: SVOM/VT optical observation
  52. GRB 250419A: Mondy Optical Observations
  53. GRB 250424A: Swift/UVOT Detection
  54. Konus-Wind detection of GRB 250424A
  55. GRB 250424A: Skynet Optical Observations
  56. GRB 250424A: Kilonova-Catcher optical afterglow detection
  57. GRB 250419a: Continued Liverpool Telescope observations
  58. GRB 250419A: Liverpool Telescope optical upper limit
  59. GRB 250407A: GRBAlpha detection
  60. GRB 250404A / EP250404a: GRBAlpha detection
  61. GRB 250330B: GRBAlpha detection
  62. GRB 250419A: SVOM/ECLAIRs refined analysis
  63. GRB 250424A: Swift-XRT refined Analysis
  64. GRB 250424A: Enhanced Swift-XRT position
  65. GRB 250424A: AstroSat CZTI detection of a bright long burst
  66. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  67. GRB 250424A: BlackGEM optical afterglow detection
  68. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  69. GRB 250424A: likely host galaxy
  70. GRB 250424A: DDOTI Afterglow Detection
  71. GRB 250424A: REM optical/NIR afterglow detection
  72. GRB 250424A: Swift detection of a burst with an optical counterpart
  73. Swift GRB 250424A: Global MASTER-Net observations report
  74. Swift GRB 250424A: Global MASTER-Net OT detection
  75. EP250421a: Nickel optical upper limit
  76. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  77. EP250421a: Upper limits from Fermi-GBM Observations
  78. SVOM/sb25042207: XRT observations
  79. SVOM/sb25042207: GOTO optical upper limits
  80. GRB 250421A: AstroSat CZTI detection
  81. GRB250419A: VLA radio detection
  82. GRB 250419A: Mephisto Multi-band Optical Detection
  83. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  84. EP250421a: NOT optical observations
  85. GRB 250419A: Optical Observations via Virtual Telescope Project
  86. EP250421a: Swift/XRT counterpart detection
  87. GRB 250419A: Mondy Continued Optical Observations
  88. Fermi GRB 250421A: Global MASTER-Net observations report
  89. GRB 250421B: AstroSat CZTI detection of a bright long burst
  90. GRB 250421A: Fermi GBM Final Real-time Localization
  91. GRB 250419A: Liverpool Telescope observations
  92. GRB 250419A: LCO optical observation
  93. GRB 250419A: JinShan optical observations
  94. GRB 250419A: SVOM/VT optical continuous observations
  95. GRB 250419A: SVOM/C-GFT optical observations
  96. GRB 250419A: Swift/UVOT Follow up
  97. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  98. GRB 250419A: LCO optical afterglow multi-band observations
  99. GRB 250419A: Mondy and AbAO Optical Observations
  100. GRB 250419A: Liverpool Telescope observations

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