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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"

21949 results found.

  1. GRB 250430A: Bassano Bresciano Observatory upper limit
  2. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  3. SVOM/sb25043004: EP-FXT observations
  4. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  5. EP 250427A: Optical counterpart detection by LCO.
  6. Swift GRB250430.73: Global MASTER-Net observations report
  7. EP250428b: FTW optical and NIR observations
  8. EP250427a/GRB250427A: HCT optical follow-up
  9. EP250427a / GRB 250427A: OHP/T193 continued photometric observations
  10. Fermi trigger No 767623859: Global MASTER-Net observations report
  11. EP250428b: SVOM/VT upper limit
  12. EP250428b: LAST optical upper limit
  13. EP250428b: Global MASTER-Net observations report
  14. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  15. EP250427a / GRB 250427A: OHP/T193 photometric observations
  16. EP250427a: EP-FXT follow-up observations
  17. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  18. EP250427a: Lesedi optical counterpart detection
  19. EP250427A: COLIBRÍ Continuing Optical Observations
  20. GRB250427A/EP250427a GIT optical afterglow detection:
  21. EP250427a: LT optical counterpart detection
  22. GRB 250427A: Swift-XRT refined Analysis
  23. EP250427a / GRB 250427A: LCO optical counterpart detection
  24. EP250427A/GRB250427A: Keck/LRIS redshift
  25. EP250427a: REM optical/NIR afterglow detection
  26. GRB 250424A: LCO optical observation
  27. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  28. EP250427A: COLIBRÍ Optical Detection
  29. EP250427a: TRT optical counterpart detection
  30. EP 250427a: BOOTES-7 optical afterglow candidate
  31. EP250427a: Global MASTER-Net observations report
  32. IceCube Alert 250426.74: Global MASTER-Net observations report
  33. GRB 250424A: PRIME near-infrared detection
  34. GRB 250424A: WINTER J-band detection
  35. GRB 250424A: EIRSAT-1 GMOD Detection
  36. GRB 250424A: SVOM/VT optical observation
  37. GRB 250419A: Mondy Optical Observations
  38. GRB 250424A: Swift/UVOT Detection
  39. Fermi-LAT gamma-ray observations of IceCube-250421A
  40. GRB 250424A: Skynet Optical Observations
  41. GRB 250424A: Kilonova-Catcher optical afterglow detection
  42. GRB 250419a: Continued Liverpool Telescope observations
  43. GRB 250419A: Liverpool Telescope optical upper limit
  44. GRB 250419A: SVOM/ECLAIRs refined analysis
  45. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  46. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  47. GRB 250424A: likely host galaxy
  48. GRB 250424A: DDOTI Afterglow Detection
  49. GRB 250424A: REM optical/NIR afterglow detection
  50. Swift GRB 250424A: Global MASTER-Net observations report
  51. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  52. EP250421a: Nickel optical upper limit
  53. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  54. EP250421a: Upper limits from Fermi-GBM Observations
  55. SVOM/sb25042207: XRT observations
  56. SVOM/sb25042207: BOOTES-2 early optical upper limit
  57. SVOM/sb25042207: GOTO optical upper limits
  58. SVOM/sb25042207: SVOM detection of an X-ray transient
  59. GRB250419A: VLA radio detection
  60. IceCube-250421A: DDOTI Detection of the LAST Candidate
  61. GRB 250419A: Mephisto Multi-band Optical Detection
  62. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  63. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  64. EP250421a: NOT optical observations
  65. GRB 250419A: Optical Observations via Virtual Telescope Project
  66. EP250421a: REM optical upper limit
  67. EP250421a: Swift/XRT counterpart detection
  68. EP250421A: COLIBRÍ Optical Upper Limit
  69. GRB 250419A: Mondy Continued Optical Observations
  70. Fermi GRB 250421A: Global MASTER-Net observations report
  71. EP250421a: Global MASTER-Net observations report
  72. EP250421a: Mephisto optical counterpart confirmation
  73. IceCube Alert 250421.71: Global MASTER-Net observations report
  74. EP250421a: JinShan likely optical counterpart
  75. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  76. GRB 250419A: Liverpool Telescope observations
  77. GRB 250419A: LCO optical observation
  78. GRB 250419A: JinShan optical observations
  79. GRB 250419A: SVOM/VT optical continuous observations
  80. GRB 250419A: SVOM/C-GFT optical observations
  81. GRB 250419A: Swift/UVOT Follow up
  82. GRB 250419A: LCO optical afterglow multi-band observations
  83. GRB 250419A: Mondy and AbAO Optical Observations
  84. GRB 250419A: Liverpool Telescope observations
  85. GRB 250419A: MASTER optical afterglow observation
  86. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  87. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  88. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  89. GRB 250419A: GOTO optical counterpart detection
  90. GRB 250419A: KAIT optical afterglow observations
  91. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  92. EP250416a: Swift/XRT counterpart fading
  93. EP250416a: refined EP-WXT and EP-FXT analysis
  94. EP20250416a: Swift/XRT counterpart detection
  95. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  96. IceCube-250416A: DDOTI Optical Observations
  97. EP250416a: Gemini South-GMOS optical counterpart
  98. EP250225a: SVOM/VT optical brightening
  99. EP250416a: GSP optical upper limit
  100. EP250416a: Global MASTER-Net observations report

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