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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"

32689 results found.

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

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