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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"

36010 results found.

  1. GRB 250502A: Swift-XRT afterglow detection
  2. GRB 250502A: NOT optical observations
  3. GRB 250502a: Liverpool Telescope optical follow-up
  4. GRB 250502B: AstroSat CZTI detection
  5. GRB 250502A: AKO Optical Afterglow Detection
  6. GRB 250502A: LCO optical counterpart detection
  7. GRB 250502A: Swift ToO observations
  8. GRB 250502A: Redshift from OSIRIS+/GTC z = 2.163
  9. GRB 250502C: Fermi GBM Final Localization
  10. GRB 250407A: VZLUSAT-2 detection
  11. GRB 250502B: DDOTI Optical Observations
  12. GRB 250430A: Swift-XRT refined Analysis
  13. GRB 250502A: Early optical counterpart detection by LCO.
  14. GRB 250430A: Swift/UVOT Detection
  15. GRB 250502A: SVOM/VT optical bump
  16. GRB 250502A: TRT optical afterglow confirmation
  17. GRB 250430A: Enhanced Swift-XRT position
  18. Fermi GRB 250502B: Global MASTER-Net observations report
  19. GRB 250430A: Optical Observations via Virtual Telescope Project, Italy
  20. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  21. GRB 250502B: Fermi GBM Final Real-time Localization
  22. GRB 250502A: SVOM detection of a burst
  23. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  24. GRB 250430A: SVOM/VT optical observations
  25. GRB 250430A: KAIT optical observations
  26. GRB 250430A / EP250430a: J-band upper limits with WINTER
  27. GRB 250430A: NUTTelA-TAO Early Measurements
  28. EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
  29. GRB 250430A: DDOTI Optical Observations
  30. GRB 250430A: Leavitt Observatory optical upper limit
  31. GRB 250430A: Bassano Bresciano Observatory upper limit
  32. GRB 250430A : MITSuME Akeno optical upper limits
  33. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  34. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  35. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  36. GRB 250430A: AKO Optical Afterglow Detection
  37. GRB 250430A: Kanata optical upper limit
  38. EP 250427A: Optical counterpart detection by LCO.
  39. GRB 250430A: Swift detection of a burst with optical counterpart
  40. EP250427a / GRB 250427A: OHP/T193 continued photometric observations
  41. EP250428b: SAO RAS optical upper limit
  42. GRB 250427A: Swift/UVOT Detection
  43. EP250427a / GRB 250427A: OHP/T193 photometric observations
  44. EP250427a: EP-FXT follow-up observations
  45. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  46. GRB250427A/EP250427a GIT optical afterglow detection:
  47. GRB 250427A: Swift-XRT refined Analysis
  48. EP250427a / GRB 250427A: LCO optical counterpart detection
  49. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  50. EP250427A/GRB250427A: Keck/LRIS redshift
  51. GRB 250424A: LCO optical observation
  52. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  53. GRB 250424A: Swift-BAT refined analysis
  54. GRB 250424A: SVOM/GRM observation of a long burst
  55. GRB 250424A: PRIME near-infrared detection
  56. GRB 250424A: WINTER J-band detection
  57. GRB 250424A: EIRSAT-1 GMOD Detection
  58. GRB 250424A: SVOM/VT optical observation
  59. GRB 250419A: Mondy Optical Observations
  60. GRB 250424A: Swift/UVOT Detection
  61. Konus-Wind detection of GRB 250424A
  62. GRB 250424A: Skynet Optical Observations
  63. GRB 250424A: Kilonova-Catcher optical afterglow detection
  64. GRB 250419a: Continued Liverpool Telescope observations
  65. GRB 250419A: Liverpool Telescope optical upper limit
  66. GRB 250407A: GRBAlpha detection
  67. GRB 250404A / EP250404a: GRBAlpha detection
  68. GRB 250330B: GRBAlpha detection
  69. GRB 250419A: SVOM/ECLAIRs refined analysis
  70. GRB 250424A: Swift-XRT refined Analysis
  71. GRB 250424A: Enhanced Swift-XRT position
  72. GRB 250424A: AstroSat CZTI detection of a bright long burst
  73. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  74. GRB 250424A: BlackGEM optical afterglow detection
  75. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  76. GRB 250424A: likely host galaxy
  77. GRB 250424A: DDOTI Afterglow Detection
  78. GRB 250424A: REM optical/NIR afterglow detection
  79. GRB 250424A: Swift detection of a burst with an optical counterpart
  80. Swift GRB 250424A: Global MASTER-Net observations report
  81. Swift GRB 250424A: Global MASTER-Net OT detection
  82. EP250421a: Nickel optical upper limit
  83. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  84. EP250421a: Upper limits from Fermi-GBM Observations
  85. SVOM/sb25042207: GOTO optical upper limits
  86. GRB 250421A: AstroSat CZTI detection
  87. GRB250419A: VLA radio detection
  88. GRB 250419A: Mephisto Multi-band Optical Detection
  89. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  90. GRB 250419A: Optical Observations via Virtual Telescope Project
  91. GRB 250419A: Mondy Continued Optical Observations
  92. Fermi GRB 250421A: Global MASTER-Net observations report
  93. GRB 250421B: AstroSat CZTI detection of a bright long burst
  94. GRB 250421A: Fermi GBM Final Real-time Localization
  95. GRB 250419A: Liverpool Telescope observations
  96. GRB 250419A: LCO optical observation
  97. GRB 250419A: JinShan optical observations
  98. GRB 250419A: SVOM/VT optical continuous observations
  99. GRB 250419A: SVOM/C-GFT optical observations
  100. GRB 250419A: Swift/UVOT Follow up

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