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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"

16099 results found.

  1. EP250427a / GRB 250427A: OHP/T193 continued photometric observations
  2. SVOM/sb25043004: SVOM detection of a X-ray transient
  3. EP250428b: GROWTH-India telescope optical upper limit
  4. EP250428b: SAO RAS optical upper limit
  5. EP250428b: LAST optical upper limit
  6. GRB 250427A: Swift/UVOT Detection
  7. EP250427a / GRB 250427A: OHP/T193 photometric observations
  8. EP250427a: EP-FXT follow-up observations
  9. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  10. EP250427a: Lesedi optical counterpart detection
  11. EP250427A: COLIBRÍ Continuing Optical Observations
  12. GRB250427A/EP250427a GIT optical afterglow detection:
  13. EP250427a: LT optical counterpart detection
  14. GRB 250427A: Swift-XRT refined Analysis
  15. EP250427a / GRB 250427A: LCO optical counterpart detection
  16. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  17. EP250427A/GRB250427A: Keck/LRIS redshift
  18. EP250427a: REM optical/NIR afterglow detection
  19. GRB 250424A: LCO optical observation
  20. EP250427A: COLIBRÍ Optical Detection
  21. EP250427a: TRT optical counterpart detection
  22. EP 250427a: BOOTES-7 optical afterglow candidate
  23. GRB 250424A: SVOM/GRM observation of a long burst
  24. GRB 250424A: PRIME near-infrared detection
  25. GRB 250424A: WINTER J-band detection
  26. GRB 250424A: SVOM/VT optical observation
  27. GRB 250419A: Mondy Optical Observations
  28. GRB 250424A: Swift/UVOT Detection
  29. Fermi-LAT gamma-ray observations of IceCube-250421A
  30. GRB 250424A: Skynet Optical Observations
  31. GRB 250424A: Kilonova-Catcher optical afterglow detection
  32. GRB 250419a: Continued Liverpool Telescope observations
  33. GRB 250419A: Liverpool Telescope optical upper limit
  34. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  35. GRB 250424A: BlackGEM optical afterglow detection
  36. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  37. GRB 250424A: likely host galaxy
  38. GRB 250424A: DDOTI Afterglow Detection
  39. GRB 250424A: REM optical/NIR afterglow detection
  40. GRB 250424A: Swift detection of a burst with an optical counterpart
  41. Swift GRB 250424A: Global MASTER-Net OT detection
  42. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  43. EP250421a: Nickel optical upper limit
  44. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  45. SVOM/sb25042207: BOOTES-2 early optical upper limit
  46. SVOM/sb25042207: GOTO optical upper limits
  47. GRB250419A: VLA radio detection
  48. GRB 250419A: Mephisto Multi-band Optical Detection
  49. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  50. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  51. EP250421a: NOT optical observations
  52. GRB 250419A: Optical Observations via Virtual Telescope Project
  53. EP250421a: REM optical upper limit
  54. EP250421a: Swift/XRT counterpart detection
  55. EP250421A: COLIBRÍ Optical Upper Limit
  56. GRB 250419A: Mondy Continued Optical Observations
  57. EP250421a: Mephisto optical counterpart confirmation
  58. EP250421a: JinShan likely optical counterpart
  59. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  60. GRB 250419A: Liverpool Telescope observations
  61. GRB 250419A: LCO optical observation
  62. GRB 250419A: JinShan optical observations
  63. GRB 250419A: SVOM/VT optical continuous observations
  64. GRB 250419A: SVOM/C-GFT optical observations
  65. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  66. GRB 250419A: LCO optical afterglow multi-band observations
  67. GRB 250419A: Mondy and AbAO Optical Observations
  68. GRB 250419A: Liverpool Telescope observations
  69. GRB 250419A: AKO Optical Afterglow Detection
  70. GRB 250419A: MASTER optical afterglow observation
  71. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  72. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  73. GRB 250419A: Swift-XRT refined Analysis
  74. GRB 250419A: GOTO optical counterpart detection
  75. GRB 250419A: KAIT optical afterglow observations
  76. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  77. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  78. GRB 250419A: SVOM detection of a soft burst
  79. EP250416a: Swift/XRT counterpart fading
  80. EP250416a: refined EP-WXT and EP-FXT analysis
  81. EP20250416a: Swift/XRT counterpart detection
  82. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  83. IceCube-250416A: DDOTI Optical Observations
  84. EP250416a: Gemini South-GMOS optical counterpart
  85. EP250225a: SVOM/VT optical brightening
  86. EP250416a: GSP optical upper limit
  87. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  88. IceCube 250414.324: DDOTI Optical Observations
  89. EP250304a: ATCA radio observations
  90. EP250404a: Nanshan 0.43m Telescope optical observatios
  91. GRB 250411A: DDOTI Optical Observations
  92. GRB 250407A: Continued KAIT/Nickel optical observations
  93. GRB 250407A: Mondy and AbAO Optical Observations
  94. EP250227a: Further NOT optical observations
  95. IceCube-250406A: Swift-XRT observations
  96. GRB 250407A: LCO detection of a fading optical counterpart
  97. GRB 250407A: SVOM/GRM observation of a bright long burst
  98. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  99. GRB 250407A: KAIT Optical Afterglow Candidate
  100. IceCube-250406A: No candidates from the Zwicky Transient Facility

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