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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"

42570 results found.

  1. GRB 250502A: Swift-XRT afterglow detection
  2. Fermi trigger No 767975731: Global MASTER-Net observations report
  3. GRB 250502A: NOT optical observations
  4. GRB 250502a: Liverpool Telescope optical follow-up
  5. GRB 250502B: AstroSat CZTI detection
  6. GRB 250502A: AKO Optical Afterglow Detection
  7. GRB 250502A: LCO optical counterpart detection
  8. GRB 250502A: Swift ToO observations
  9. GRB 250502A: Redshift from OSIRIS+/GTC z = 2.163
  10. GRB 250502C: Fermi GBM Final Localization
  11. Fermi-LAT Gamma-ray Observations of IceCube-250429A
  12. GRB 250502B: DDOTI Optical Observations
  13. GRB 250430A: Swift-XRT refined Analysis
  14. GRB 250502A: Early optical counterpart detection by LCO.
  15. GRB 250430A: Swift/UVOT Detection
  16. GRB 250502A: SVOM/VT optical bump
  17. GRB 250502A: TRT optical afterglow confirmation
  18. GRB 250430A: Enhanced Swift-XRT position
  19. Fermi GRB 250502B: Global MASTER-Net observations report
  20. GRB 250430A: Optical Observations via Virtual Telescope Project, Italy
  21. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  22. GRB 250502B: Fermi GBM Final Real-time Localization
  23. GRB 250502A: SVOM detection of a burst
  24. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  25. GRB 250430A: SVOM/VT optical observations
  26. GRB 250430A: KAIT optical observations
  27. EP250428b: Pan-STARRS follow-up, upper limit on the optical counterpart, and possible host galaxy.
  28. GRB 250430A / EP250430a: J-band upper limits with WINTER
  29. GRB 250430A: NUTTelA-TAO Early Measurements
  30. EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
  31. GRB 250430A: DDOTI Optical Observations
  32. GRB 250430A: Leavitt Observatory optical upper limit
  33. GRB 250430A: Bassano Bresciano Observatory upper limit
  34. GRB 250430A : MITSuME Akeno optical upper limits
  35. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  36. SVOM/sb25043004: EP-FXT observations
  37. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  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. GRB 250430A: Swift detection of a burst with optical counterpart
  44. Swift GRB250430.73: Global MASTER-Net observations report
  45. EP250428b: FTW optical and NIR observations
  46. EP250427a/GRB250427A: HCT optical follow-up
  47. EP250427a / GRB 250427A: OHP/T193 continued photometric observations
  48. SVOM/sb25043004: SVOM detection of a X-ray transient
  49. Fermi trigger No 767623859: Global MASTER-Net observations report
  50. EP250428b: refined analysis of the EP-FXT follow-up observation
  51. EP250428b: GROWTH-India telescope optical upper limit
  52. EP250428b: SVOM/VT upper limit
  53. EP250428b: SAO RAS optical upper limit
  54. EP250428b: LAST optical upper limit
  55. IceCube-250429A - IceCube observation of a high-energy neutrino candidate track-like event
  56. GRB 250427A: Swift/UVOT Detection
  57. EP250428b: Global MASTER-Net observations report
  58. EP250428b: Einstein Probe detection of a fast X-ray transient
  59. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  60. EP250427a / GRB 250427A: OHP/T193 photometric observations
  61. EP250427a: EP-FXT follow-up observations
  62. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  63. EP250427a: Lesedi optical counterpart detection
  64. EP250427A: COLIBRÍ Continuing Optical Observations
  65. GRB250427A/EP250427a GIT optical afterglow detection:
  66. EP250427a: LT optical counterpart detection
  67. GRB 250427A: Swift-XRT refined Analysis
  68. EP250427a / GRB 250427A: LCO optical counterpart detection
  69. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  70. EP250427A/GRB250427A: Keck/LRIS redshift
  71. EP250427a: REM optical/NIR afterglow detection
  72. GRB 250424A: LCO optical observation
  73. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  74. EP250427A: COLIBRÍ Optical Detection
  75. EP250427a: TRT optical counterpart detection
  76. EP 250427a: BOOTES-7 optical afterglow candidate
  77. EP250427a: Global MASTER-Net observations report
  78. EP250427a: Einstein Probe detection of a fast X-ray transient
  79. IceCube Alert 250426.74: Global MASTER-Net observations report
  80. GRB 250424A: Swift-BAT refined analysis
  81. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event
  82. GRB 250424A: SVOM/GRM observation of a long burst
  83. GRB 250424A: PRIME near-infrared detection
  84. GRB 250424A: WINTER J-band detection
  85. GRB 250424A: EIRSAT-1 GMOD Detection
  86. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  87. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  88. GRB 250424A: SVOM/VT optical observation
  89. GRB 250419A: Mondy Optical Observations
  90. GRB 250424A: Swift/UVOT Detection
  91. Konus-Wind detection of GRB 250424A
  92. Fermi-LAT gamma-ray observations of IceCube-250421A
  93. GRB 250424A: Skynet Optical Observations
  94. GRB 250424A: Kilonova-Catcher optical afterglow detection
  95. GRB 250419a: Continued Liverpool Telescope observations
  96. GRB 250419A: Liverpool Telescope optical upper limit
  97. GRB 250419A: SVOM/ECLAIRs refined analysis
  98. GRB 250424A: Swift-XRT refined Analysis
  99. GRB 250424A: Enhanced Swift-XRT position
  100. GRB 250424A: AstroSat CZTI detection of a bright long burst

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