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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 250502A: Bassano Bresciano Observatory upper limit
  2. GRB 250430A: Konus-Wind detection and joint Konus-Wind+Swift-BAT spectral analysis
  3. GRB 250506A: Xinglong 2.16m optical upper limit
  4. SVOM/sb25050601: EP-FXT observations
  5. GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
  6. GRB 250506A: REM optical/NIR upper limits
  7. GRB 250506A: Fermi GBM Observation
  8. GRB 250506A: Swift XRT observations and possible counterpart detection
  9. GRB 250506A: TRT optical observations
  10. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
  11. GRB 250504A: Swift-BAT refined analysis
  12. GRB 250430A: Swift-BAT refined analysis
  13. GRB 250504A: VLT/X-shooter upper limits
  14. Fermi GRB 250505A: Global MASTER-Net observations report
  15. GRB 250504A: SVOM/VT upper limit
  16. GRB 250504A: REM optical/NIR observations
  17. GRB 250502A: REM optical/NIR observations
  18. GRB 250504A: MeerLICHT optical afterglow detection
  19. GRB 250504A: Fermi GBM Observation
  20. Fermi GRB 250504A: Global MASTER-Net observations report
  21. GRB 250502A: Swift/UVOT Follow up
  22. GRB 250502A: Mondy and Tien-Shan Optical Observations
  23. GRB 250502A: KAIT optical observations
  24. GRB 250502A: Montarrenti Observatory optical detection
  25. GRB 250502A: Swift-XRT afterglow detection
  26. GRB 250502A: NOT optical observations
  27. GRB 250502a: Liverpool Telescope optical follow-up
  28. GRB 250502B: AstroSat CZTI detection
  29. GRB 250502A: AKO Optical Afterglow Detection
  30. GRB 250502A: LCO optical counterpart detection
  31. GRB 250502A: Swift ToO observations
  32. GRB 250502A: Redshift from OSIRIS+/GTC z = 2.163
  33. GRB 250407A: VZLUSAT-2 detection
  34. Fermi-LAT Gamma-ray Observations of IceCube-250429A
  35. GRB 250502B: DDOTI Optical Observations
  36. GRB 250502A: Early optical counterpart detection by LCO.
  37. GRB 250430A: Swift/UVOT Detection
  38. GRB 250502A: SVOM/VT optical bump
  39. GRB 250502A: TRT optical afterglow confirmation
  40. Fermi GRB 250502B: Global MASTER-Net observations report
  41. GRB 250430A: Optical Observations via Virtual Telescope Project, Italy
  42. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  43. GRB 250430A: SVOM/VT optical observations
  44. GRB 250430A: KAIT optical observations
  45. EP250428b: Pan-STARRS follow-up, upper limit on the optical counterpart, and possible host galaxy.
  46. GRB 250430A / EP250430a: J-band upper limits with WINTER
  47. GRB 250430A: NUTTelA-TAO Early Measurements
  48. EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
  49. GRB 250430A: DDOTI Optical Observations
  50. GRB 250430A: Leavitt Observatory optical upper limit
  51. GRB 250430A: Bassano Bresciano Observatory upper limit
  52. GRB 250430A : MITSuME Akeno optical upper limits
  53. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  54. SVOM/sb25043004: EP-FXT observations
  55. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  56. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  57. IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
  58. IceCube-250426A: Upper limits from a search for additional neutrino events in IceCube
  59. GRB 250430A: AKO Optical Afterglow Detection
  60. GRB 250430A: Kanata optical upper limit
  61. EP 250427A: Optical counterpart detection by LCO.
  62. EP250428b: FTW optical and NIR observations
  63. EP250427a/GRB250427A: HCT optical follow-up
  64. EP250427a / GRB 250427A: OHP/T193 continued photometric observations
  65. EP250428b: refined analysis of the EP-FXT follow-up observation
  66. EP250428b: GROWTH-India telescope optical upper limit
  67. EP250428b: SVOM/VT upper limit
  68. EP250428b: SAO RAS optical upper limit
  69. EP250428b: LAST optical upper limit
  70. GRB 250427A: Swift/UVOT Detection
  71. EP250428b: Global MASTER-Net observations report
  72. EP250428b: Einstein Probe detection of a fast X-ray transient
  73. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  74. EP250427a / GRB 250427A: OHP/T193 photometric observations
  75. EP250427a: EP-FXT follow-up observations
  76. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  77. EP250427a: Lesedi optical counterpart detection
  78. EP250427A: COLIBRÍ Continuing Optical Observations
  79. GRB250427A/EP250427a GIT optical afterglow detection:
  80. EP250427a: LT optical counterpart detection
  81. GRB 250427A: Swift-XRT refined Analysis
  82. EP250427a / GRB 250427A: LCO optical counterpart detection
  83. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  84. EP250427A/GRB250427A: Keck/LRIS redshift
  85. EP250427a: REM optical/NIR afterglow detection
  86. GRB 250424A: LCO optical observation
  87. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  88. EP250427A: COLIBRÍ Optical Detection
  89. EP250427a: TRT optical counterpart detection
  90. EP250427a: Global MASTER-Net observations report
  91. EP250427a: Einstein Probe detection of a fast X-ray transient
  92. GRB 250424A: Swift-BAT refined analysis
  93. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event (duplicate submission)
  94. GRB 250424A: SVOM/GRM observation of a long burst
  95. GRB 250424A: PRIME near-infrared detection
  96. GRB 250424A: WINTER J-band detection
  97. GRB 250424A: EIRSAT-1 GMOD Detection
  98. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  99. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  100. GRB 250424A: SVOM/VT optical observation

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