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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"

32688 results found.

  1. GRB 250430A: Konus-Wind detection and joint Konus-Wind+Swift-BAT spectral analysis
  2. GRB 250506A: Xinglong 2.16m optical upper limit
  3. SVOM/sb25050601: EP-FXT observations
  4. GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
  5. GRB 250506A: REM optical/NIR upper limits
  6. GRB 250506A: Fermi GBM Observation
  7. GRB 250506A: Swift XRT observations and possible counterpart detection
  8. GRB 250506A: TRT optical observations
  9. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
  10. GRB 250504A: Swift-BAT refined analysis
  11. GRB 250430A: Swift-BAT 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 250504A: MeerLICHT optical afterglow detection
  18. GRB 250504A: Fermi GBM Observation
  19. Fermi GRB 250504A: Global MASTER-Net observations report
  20. GRB 250502A: Swift/UVOT Follow up
  21. GRB 250502A: Mondy and Tien-Shan Optical Observations
  22. GRB 250502A: KAIT optical observations
  23. GRB 250502A: Montarrenti Observatory optical detection
  24. GRB 250502A: Swift-XRT afterglow detection
  25. GRB 250502A: NOT optical observations
  26. GRB 250502a: Liverpool Telescope optical follow-up
  27. GRB 250502B: AstroSat CZTI detection
  28. GRB 250502A: AKO Optical Afterglow Detection
  29. GRB 250502A: LCO optical counterpart detection
  30. GRB 250502A: Swift ToO observations
  31. GRB 250502A: Redshift from OSIRIS+/GTC z = 2.163
  32. GRB 250407A: VZLUSAT-2 detection
  33. Fermi-LAT Gamma-ray Observations of IceCube-250429A
  34. GRB 250502B: DDOTI Optical Observations
  35. GRB 250502A: Early optical counterpart detection by LCO.
  36. GRB 250430A: Swift/UVOT Detection
  37. GRB 250502A: SVOM/VT optical bump
  38. GRB 250502A: TRT optical afterglow confirmation
  39. Fermi GRB 250502B: Global MASTER-Net observations report
  40. GRB 250430A: Optical Observations via Virtual Telescope Project, Italy
  41. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  42. GRB 250430A: SVOM/VT optical observations
  43. GRB 250430A: KAIT optical observations
  44. EP250428b: Pan-STARRS follow-up, upper limit on the optical counterpart, and possible host galaxy.
  45. GRB 250430A / EP250430a: J-band upper limits with WINTER
  46. GRB 250430A: NUTTelA-TAO Early Measurements
  47. EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
  48. GRB 250430A: DDOTI Optical Observations
  49. GRB 250430A: Leavitt Observatory optical upper limit
  50. GRB 250430A: Bassano Bresciano Observatory upper limit
  51. GRB 250430A : MITSuME Akeno optical upper limits
  52. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  53. SVOM/sb25043004: EP-FXT observations
  54. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  55. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  56. IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
  57. IceCube-250426A: Upper limits from a search for additional neutrino events in IceCube
  58. GRB 250430A: AKO Optical Afterglow Detection
  59. GRB 250430A: Kanata optical upper limit
  60. EP 250427A: Optical counterpart detection by LCO.
  61. EP250428b: FTW optical and NIR observations
  62. EP250427a/GRB250427A: HCT optical follow-up
  63. EP250427a / GRB 250427A: OHP/T193 continued photometric observations
  64. EP250428b: refined analysis of the EP-FXT follow-up observation
  65. EP250428b: GROWTH-India telescope optical upper limit
  66. EP250428b: SVOM/VT upper limit
  67. EP250428b: SAO RAS optical upper limit
  68. EP250428b: LAST optical upper limit
  69. GRB 250427A: Swift/UVOT Detection
  70. EP250428b: Global MASTER-Net observations report
  71. EP250428b: Einstein Probe detection of a fast X-ray transient
  72. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  73. EP250427a / GRB 250427A: OHP/T193 photometric observations
  74. EP250427a: EP-FXT follow-up observations
  75. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  76. EP250427a: Lesedi optical counterpart detection
  77. EP250427A: COLIBRÍ Continuing Optical Observations
  78. GRB250427A/EP250427a GIT optical afterglow detection:
  79. EP250427a: LT optical counterpart detection
  80. GRB 250427A: Swift-XRT refined Analysis
  81. EP250427a / GRB 250427A: LCO optical counterpart detection
  82. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  83. EP250427A/GRB250427A: Keck/LRIS redshift
  84. EP250427a: REM optical/NIR afterglow detection
  85. GRB 250424A: LCO optical observation
  86. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  87. EP250427A: COLIBRÍ Optical Detection
  88. EP250427a: TRT optical counterpart detection
  89. EP250427a: Global MASTER-Net observations report
  90. EP250427a: Einstein Probe detection of a fast X-ray transient
  91. GRB 250424A: Swift-BAT refined analysis
  92. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event (duplicate submission)
  93. GRB 250424A: SVOM/GRM observation of a long burst
  94. GRB 250424A: PRIME near-infrared detection
  95. GRB 250424A: WINTER J-band detection
  96. GRB 250424A: EIRSAT-1 GMOD Detection
  97. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  98. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  99. GRB 250424A: SVOM/VT optical observation
  100. GRB 250419A: Mondy Optical Observations

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