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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"

32569 results found.

  1. Fermi GRB 250504A: Global MASTER-Net observations report
  2. GRB 250502A: Swift/UVOT Follow up
  3. GRB 250502A: Mondy and Tien-Shan Optical Observations
  4. GRB 250502A: KAIT optical observations
  5. GRB 250502A: Montarrenti Observatory optical detection
  6. GRB 250502A: Swift-XRT afterglow detection
  7. GRB 250502A: NOT optical observations
  8. GRB 250502a: Liverpool Telescope optical follow-up
  9. GRB 250502B: AstroSat CZTI detection
  10. GRB 250502A: AKO Optical Afterglow Detection
  11. GRB 250502A: LCO optical counterpart detection
  12. GRB 250502A: Swift ToO observations
  13. GRB 250502A: Redshift from OSIRIS+/GTC z = 2.163
  14. GRB 250407A: VZLUSAT-2 detection
  15. Fermi-LAT Gamma-ray Observations of IceCube-250429A
  16. GRB 250502B: DDOTI Optical Observations
  17. GRB 250502A: Early optical counterpart detection by LCO.
  18. GRB 250430A: Swift/UVOT Detection
  19. GRB 250502A: SVOM/VT optical bump
  20. GRB 250502A: TRT optical afterglow confirmation
  21. Fermi GRB 250502B: Global MASTER-Net observations report
  22. GRB 250430A: Optical Observations via Virtual Telescope Project, Italy
  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. EP250428b: Pan-STARRS follow-up, upper limit on the optical counterpart, and possible host galaxy.
  27. GRB 250430A / EP250430a: J-band upper limits with WINTER
  28. GRB 250430A: NUTTelA-TAO Early Measurements
  29. EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
  30. GRB 250430A: DDOTI Optical Observations
  31. GRB 250430A: Leavitt Observatory optical upper limit
  32. GRB 250430A: Bassano Bresciano Observatory upper limit
  33. GRB 250430A : MITSuME Akeno optical upper limits
  34. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  35. SVOM/sb25043004: EP-FXT observations
  36. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  37. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  38. IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
  39. IceCube-250426A: Upper limits from a search for additional neutrino events in IceCube
  40. GRB 250430A: AKO Optical Afterglow Detection
  41. GRB 250430A: Kanata optical upper limit
  42. EP 250427A: Optical counterpart detection by LCO.
  43. EP250428b: FTW optical and NIR observations
  44. EP250427a/GRB250427A: HCT optical follow-up
  45. EP250427a / GRB 250427A: OHP/T193 continued photometric observations
  46. EP250428b: refined analysis of the EP-FXT follow-up observation
  47. EP250428b: GROWTH-India telescope optical upper limit
  48. EP250428b: SVOM/VT upper limit
  49. EP250428b: SAO RAS optical upper limit
  50. EP250428b: LAST optical upper limit
  51. GRB 250427A: Swift/UVOT Detection
  52. EP250428b: Global MASTER-Net observations report
  53. EP250428b: Einstein Probe detection of a fast X-ray transient
  54. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  55. EP250427a / GRB 250427A: OHP/T193 photometric observations
  56. EP250427a: EP-FXT follow-up observations
  57. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  58. EP250427a: Lesedi optical counterpart detection
  59. EP250427A: COLIBRÍ Continuing Optical Observations
  60. GRB250427A/EP250427a GIT optical afterglow detection:
  61. EP250427a: LT optical counterpart detection
  62. GRB 250427A: Swift-XRT refined Analysis
  63. EP250427a / GRB 250427A: LCO optical counterpart detection
  64. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  65. EP250427A/GRB250427A: Keck/LRIS redshift
  66. EP250427a: REM optical/NIR afterglow detection
  67. GRB 250424A: LCO optical observation
  68. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  69. EP250427A: COLIBRÍ Optical Detection
  70. EP250427a: TRT optical counterpart detection
  71. EP250427a: Global MASTER-Net observations report
  72. EP250427a: Einstein Probe detection of a fast X-ray transient
  73. GRB 250424A: Swift-BAT refined analysis
  74. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event (duplicate submission)
  75. GRB 250424A: SVOM/GRM observation of a long burst
  76. GRB 250424A: PRIME near-infrared detection
  77. GRB 250424A: WINTER J-band detection
  78. GRB 250424A: EIRSAT-1 GMOD Detection
  79. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  80. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  81. GRB 250424A: SVOM/VT optical observation
  82. GRB 250419A: Mondy Optical Observations
  83. GRB 250424A: Swift/UVOT Detection
  84. Konus-Wind detection of GRB 250424A
  85. Fermi-LAT gamma-ray observations of IceCube-250421A
  86. GRB 250424A: Skynet Optical Observations
  87. GRB 250424A: Kilonova-Catcher optical afterglow detection
  88. GRB 250419a: Continued Liverpool Telescope observations
  89. GRB 250419A: Liverpool Telescope optical upper limit
  90. GRB 250407A: GRBAlpha detection
  91. GRB 250404A / EP250404a: GRBAlpha detection
  92. GRB 250330B: GRBAlpha detection
  93. GRB 250419A: SVOM/ECLAIRs refined analysis
  94. GRB 250424A: AstroSat CZTI detection of a bright long burst
  95. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  96. GRB 250424A: BlackGEM optical afterglow detection
  97. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  98. GRB 250424A: likely host galaxy
  99. GRB 250424A: DDOTI Afterglow Detection
  100. GRB 250424A: REM optical/NIR afterglow detection

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