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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"

45942 results found.

  1. GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
  2. GRB 250506A: REM optical/NIR upper limits
  3. GRB 250506A: Fermi GBM Observation
  4. GRB 250506A: Swift XRT observations and possible counterpart detection
  5. GRB 250506A: TRT optical observations
  6. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
  7. GRB 250506A: SVOM detection of a burst
  8. GRB 250504A: Swift-BAT refined analysis
  9. GRB 250430A: Swift-BAT refined analysis
  10. GRB 250506A: Fermi GBM Final Real-time Localization
  11. GRB 250504A: Swift-XRT refined Analysis
  12. GRB 250504A: VLT/X-shooter upper limits
  13. Fermi GRB 250505A: Global MASTER-Net observations report
  14. GRB 250504A: SVOM/VT upper limit
  15. GRB 250504A: REM optical/NIR observations
  16. GRB 250502A: REM optical/NIR observations
  17. GRB 250505A: Fermi GBM Final Real-time Localization
  18. GRB 250504A: MeerLICHT optical afterglow detection
  19. GRB 250504A: Fermi GBM Observation
  20. GRB 250504A: Enhanced Swift-XRT position
  21. Fermi GRB 250504A: Global MASTER-Net observations report
  22. GRB 250504A: Swift detection of a burst
  23. GRB 250504A: Fermi GBM Final Real-time Localization
  24. Swift GRB250504.98: Global MASTER-Net observations report
  25. GRB 250502A: Swift/UVOT Follow up
  26. GRB 250502A: Mondy and Tien-Shan Optical Observations
  27. GRB 250502A: KAIT optical observations
  28. GRB 250502A: Montarrenti Observatory optical detection
  29. GRB 250502A: Swift-XRT afterglow detection
  30. Fermi trigger No 767975731: Global MASTER-Net observations report
  31. GRB 250502A: NOT optical observations
  32. GRB 250502a: Liverpool Telescope optical follow-up
  33. GRB 250502B: AstroSat CZTI detection
  34. GRB 250502A: AKO Optical Afterglow Detection
  35. GRB 250502A: LCO optical counterpart detection
  36. GRB 250502A: Swift ToO observations
  37. GRB 250502A: Redshift from OSIRIS+/GTC z = 2.163
  38. GRB 250502C: Fermi GBM Final Localization
  39. GRB 250407A: VZLUSAT-2 detection
  40. Fermi-LAT Gamma-ray Observations of IceCube-250429A
  41. GRB 250502B: DDOTI Optical Observations
  42. GRB 250430A: Swift-XRT refined Analysis
  43. GRB 250502A: Early optical counterpart detection by LCO.
  44. GRB 250430A: Swift/UVOT Detection
  45. GRB 250502A: SVOM/VT optical bump
  46. GRB 250502A: TRT optical afterglow confirmation
  47. GRB 250430A: Enhanced Swift-XRT position
  48. Fermi GRB 250502B: Global MASTER-Net observations report
  49. GRB 250430A: Optical Observations via Virtual Telescope Project, Italy
  50. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  51. GRB 250502B: Fermi GBM Final Real-time Localization
  52. GRB 250502A: SVOM detection of a burst
  53. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  54. GRB 250430A: SVOM/VT optical observations
  55. GRB 250430A: KAIT optical observations
  56. EP250428b: Pan-STARRS follow-up, upper limit on the optical counterpart, and possible host galaxy.
  57. GRB 250430A / EP250430a: J-band upper limits with WINTER
  58. GRB 250430A: NUTTelA-TAO Early Measurements
  59. EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
  60. GRB 250430A: DDOTI Optical Observations
  61. GRB 250430A: Leavitt Observatory optical upper limit
  62. GRB 250430A: Bassano Bresciano Observatory upper limit
  63. GRB 250430A : MITSuME Akeno optical upper limits
  64. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  65. SVOM/sb25043004: EP-FXT observations
  66. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  67. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  68. IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
  69. IceCube-250426A: Upper limits from a search for additional neutrino events in IceCube
  70. GRB 250430A: AKO Optical Afterglow Detection
  71. GRB 250430A: Kanata optical upper limit
  72. EP 250427A: Optical counterpart detection by LCO.
  73. GRB 250430A: Swift detection of a burst with optical counterpart
  74. Swift GRB250430.73: Global MASTER-Net observations report
  75. EP250428b: FTW optical and NIR observations
  76. EP250427a/GRB250427A: HCT optical follow-up
  77. EP250427a / GRB 250427A: OHP/T193 continued photometric observations
  78. SVOM/sb25043004: SVOM detection of a X-ray transient
  79. Fermi trigger No 767623859: Global MASTER-Net observations report
  80. EP250428b: refined analysis of the EP-FXT follow-up observation
  81. EP250428b: GROWTH-India telescope optical upper limit
  82. EP250428b: SVOM/VT upper limit
  83. EP250428b: SAO RAS optical upper limit
  84. EP250428b: LAST optical upper limit
  85. IceCube-250429A - IceCube observation of a high-energy neutrino candidate track-like event
  86. GRB 250427A: Swift/UVOT Detection
  87. EP250428b: Global MASTER-Net observations report
  88. EP250428b: Einstein Probe detection of a fast X-ray transient
  89. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  90. EP250427a / GRB 250427A: OHP/T193 photometric observations
  91. EP250427a: EP-FXT follow-up observations
  92. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  93. EP250427a: Lesedi optical counterpart detection
  94. EP250427A: COLIBRÍ Continuing Optical Observations
  95. GRB250427A/EP250427a GIT optical afterglow detection:
  96. EP250427a: LT optical counterpart detection
  97. GRB 250427A: Swift-XRT refined Analysis
  98. EP250427a / GRB 250427A: LCO optical counterpart detection
  99. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  100. EP250427A/GRB250427A: Keck/LRIS redshift

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