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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. 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"

19549 results found.

  1. GRB 250502A: Redshift from OSIRIS+/GTC z = 2.163
  2. GRB 250502B: DDOTI Optical Observations
  3. GRB 250502A: Early optical counterpart detection by LCO.
  4. GRB 250430A: Swift/UVOT Detection
  5. GRB 250502A: TRT optical afterglow confirmation
  6. GRB 250430A: Enhanced Swift-XRT position
  7. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  8. GRB 250502A: SVOM detection of a burst
  9. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  10. GRB 250430A: KAIT optical observations
  11. GRB 250430A / EP250430a: J-band upper limits with WINTER
  12. GRB 250430A: DDOTI Optical Observations
  13. GRB 250430A: Leavitt Observatory optical upper limit
  14. GRB 250430A: Bassano Bresciano Observatory upper limit
  15. GRB 250430A : MITSuME Akeno optical upper limits
  16. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  17. GRB 250430A: AKO Optical Afterglow Detection
  18. GRB 250430A: Kanata optical upper limit
  19. EP 250427A: Optical counterpart detection by LCO.
  20. GRB 250430A: Swift detection of a burst with optical counterpart
  21. EP250427a/GRB250427A: HCT optical follow-up
  22. SVOM/sb25043004: SVOM detection of a X-ray transient
  23. EP250428b: GROWTH-India telescope optical upper limit
  24. EP250428b: SAO RAS optical upper limit
  25. EP250428b: LAST optical upper limit
  26. GRB 250427A: Swift/UVOT Detection
  27. EP250428b: Einstein Probe detection of a fast X-ray transient
  28. EP250427A: COLIBRÍ Continuing Optical Observations
  29. GRB250427A/EP250427a GIT optical afterglow detection:
  30. EP250427a: LT optical counterpart detection
  31. EP250427a / GRB 250427A: LCO optical counterpart detection
  32. EP250427a: REM optical/NIR afterglow detection
  33. GRB 250424A: LCO optical observation
  34. EP250427A: COLIBRÍ Optical Detection
  35. EP250427a: TRT optical counterpart detection
  36. EP250427a: Global MASTER-Net observations report
  37. EP250427a: Einstein Probe detection of a fast X-ray transient
  38. GRB 250424A: SVOM/GRM observation of a long burst
  39. GRB 250424A: PRIME near-infrared detection
  40. GRB 250424A: WINTER J-band detection
  41. GRB 250419A: Mondy Optical Observations
  42. GRB 250424A: Swift/UVOT Detection
  43. Fermi-LAT gamma-ray observations of IceCube-250421A
  44. GRB 250424A: Skynet Optical Observations
  45. GRB 250424A: Kilonova-Catcher optical afterglow detection
  46. GRB 250419A: SVOM/ECLAIRs refined analysis
  47. GRB 250424A: Enhanced Swift-XRT position
  48. GRB 250424A: AstroSat CZTI detection of a bright long burst
  49. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  50. GRB 250424A: BlackGEM optical afterglow detection
  51. GRB 250424A: DDOTI Afterglow Detection
  52. GRB 250424A: REM optical/NIR afterglow detection
  53. GRB 250424A: Swift detection of a burst with an optical counterpart
  54. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  55. EP250421a: Nickel optical upper limit
  56. SVOM/sb25042207: XRT observations
  57. SVOM/sb25042207: SVOM detection of an X-ray transient
  58. IceCube-250421A: DDOTI Detection of the LAST Candidate
  59. GRB 250419A: Mephisto Multi-band Optical Detection
  60. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  61. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  62. EP250421a: NOT optical observations
  63. GRB 250419A: Optical Observations via Virtual Telescope Project
  64. EP250421a: REM optical upper limit
  65. EP250421A: COLIBRÍ Optical Upper Limit
  66. GRB 250419A: Mondy Continued Optical Observations
  67. GRB 250421B: AstroSat CZTI detection of a bright long burst
  68. EP250421a: Einstein Probe detection of an X-ray transient
  69. EP250421a: Mephisto optical counterpart confirmation
  70. EP250421a: JinShan likely optical counterpart
  71. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  72. GRB 250419A: LCO optical observation
  73. GRB 250419A: JinShan optical observations
  74. GRB 250419A: SVOM/C-GFT optical observations
  75. GRB 250419A: Swift/UVOT Follow up
  76. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  77. GRB 250419A: LCO optical afterglow multi-band observations
  78. GRB 250419A: Mondy and AbAO Optical Observations
  79. GRB 250419A: AKO Optical Afterglow Detection
  80. GRB 250419A: KAIT optical afterglow observations
  81. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  82. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  83. GRB 250419A: SVOM detection of a soft burst
  84. EP250416a: refined EP-WXT and EP-FXT analysis
  85. EP20250416a: Swift/XRT counterpart detection
  86. IceCube-250416A: DDOTI Optical Observations
  87. EP250416a: Gemini South-GMOS optical counterpart
  88. SVOM/sb25041603 is not a GRB
  89. EP250416a: GSP optical upper limit
  90. EP250416a: Einstein Probe detection of an X-ray transient
  91. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  92. SVOM/sb25041603: SVOM detection of an X-ray transient
  93. IceCube 250414.324: DDOTI Optical Observations
  94. GRB 250413A: AstroSat CZTI detection
  95. EP250404a: Nanshan 0.43m Telescope optical observatios
  96. GRB 250411A: DDOTI Optical Observations
  97. GRB 250314A: e-MERLIN observations
  98. GRB 250407A: Mondy and AbAO Optical Observations
  99. EP250227a: Further NOT optical observations
  100. GRB 250320B: cubesat Avion detection

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