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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"

21946 results found.

  1. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  2. EP 250427A: Optical counterpart detection by LCO.
  3. Swift GRB250430.73: Global MASTER-Net observations report
  4. EP250428b: FTW optical and NIR observations
  5. EP250427a/GRB250427A: HCT optical follow-up
  6. EP250427a / GRB 250427A: OHP/T193 continued photometric observations
  7. Fermi trigger No 767623859: Global MASTER-Net observations report
  8. EP250428b: SVOM/VT upper limit
  9. EP250428b: LAST optical upper limit
  10. EP250428b: Global MASTER-Net observations report
  11. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  12. EP250427a / GRB 250427A: OHP/T193 photometric observations
  13. EP250427a: EP-FXT follow-up observations
  14. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  15. EP250427a: Lesedi optical counterpart detection
  16. EP250427A: COLIBRÍ Continuing Optical Observations
  17. GRB250427A/EP250427a GIT optical afterglow detection:
  18. EP250427a: LT optical counterpart detection
  19. GRB 250427A: Swift-XRT refined Analysis
  20. EP250427a / GRB 250427A: LCO optical counterpart detection
  21. EP250427A/GRB250427A: Keck/LRIS redshift
  22. EP250427a: REM optical/NIR afterglow detection
  23. GRB 250424A: LCO optical observation
  24. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  25. EP250427A: COLIBRÍ Optical Detection
  26. EP250427a: TRT optical counterpart detection
  27. EP 250427a: BOOTES-7 optical afterglow candidate
  28. EP250427a: Global MASTER-Net observations report
  29. IceCube Alert 250426.74: Global MASTER-Net observations report
  30. GRB 250424A: PRIME near-infrared detection
  31. GRB 250424A: WINTER J-band detection
  32. GRB 250424A: EIRSAT-1 GMOD Detection
  33. GRB 250424A: SVOM/VT optical observation
  34. GRB 250419A: Mondy Optical Observations
  35. GRB 250424A: Swift/UVOT Detection
  36. Fermi-LAT gamma-ray observations of IceCube-250421A
  37. GRB 250424A: Skynet Optical Observations
  38. GRB 250424A: Kilonova-Catcher optical afterglow detection
  39. GRB 250419a: Continued Liverpool Telescope observations
  40. GRB 250419A: Liverpool Telescope optical upper limit
  41. GRB 250419A: SVOM/ECLAIRs refined analysis
  42. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  43. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  44. GRB 250424A: likely host galaxy
  45. GRB 250424A: DDOTI Afterglow Detection
  46. GRB 250424A: REM optical/NIR afterglow detection
  47. Swift GRB 250424A: Global MASTER-Net observations report
  48. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  49. EP250421a: Nickel optical upper limit
  50. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  51. EP250421a: Upper limits from Fermi-GBM Observations
  52. SVOM/sb25042207: XRT observations
  53. SVOM/sb25042207: BOOTES-2 early optical upper limit
  54. SVOM/sb25042207: GOTO optical upper limits
  55. SVOM/sb25042207: SVOM detection of an X-ray transient
  56. GRB250419A: VLA radio detection
  57. IceCube-250421A: DDOTI Detection of the LAST Candidate
  58. GRB 250419A: Mephisto Multi-band Optical Detection
  59. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  60. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  61. EP250421a: NOT optical observations
  62. GRB 250419A: Optical Observations via Virtual Telescope Project
  63. EP250421a: REM optical upper limit
  64. EP250421a: Swift/XRT counterpart detection
  65. EP250421A: COLIBRÍ Optical Upper Limit
  66. GRB 250419A: Mondy Continued Optical Observations
  67. Fermi GRB 250421A: Global MASTER-Net observations report
  68. EP250421a: Global MASTER-Net observations report
  69. EP250421a: Mephisto optical counterpart confirmation
  70. IceCube Alert 250421.71: Global MASTER-Net observations report
  71. EP250421a: JinShan likely optical counterpart
  72. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  73. GRB 250419A: Liverpool Telescope observations
  74. GRB 250419A: LCO optical observation
  75. GRB 250419A: JinShan optical observations
  76. GRB 250419A: SVOM/VT optical continuous observations
  77. GRB 250419A: SVOM/C-GFT optical observations
  78. GRB 250419A: Swift/UVOT Follow up
  79. GRB 250419A: LCO optical afterglow multi-band observations
  80. GRB 250419A: Mondy and AbAO Optical Observations
  81. GRB 250419A: Liverpool Telescope observations
  82. GRB 250419A: MASTER optical afterglow observation
  83. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  84. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  85. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  86. GRB 250419A: GOTO optical counterpart detection
  87. GRB 250419A: KAIT optical afterglow observations
  88. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  89. EP250416a: Swift/XRT counterpart fading
  90. EP250416a: refined EP-WXT and EP-FXT analysis
  91. EP20250416a: Swift/XRT counterpart detection
  92. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  93. IceCube-250416A: DDOTI Optical Observations
  94. EP250416a: Gemini South-GMOS optical counterpart
  95. EP250225a: SVOM/VT optical brightening
  96. EP250416a: GSP optical upper limit
  97. EP250416a: Global MASTER-Net observations report
  98. IceCube-250416A: Global MASTER-Net observations report
  99. IceCube 250414.324: DDOTI Optical Observations
  100. EP250304a: ATCA radio observations

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