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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.

Lucene Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

23209 results found.

  1. EP250428b: refined analysis of the EP-FXT follow-up observation
  2. EP250428b: GROWTH-India telescope optical upper limit
  3. EP250428b: SAO RAS optical upper limit
  4. EP250428b: LAST optical upper limit
  5. GRB 250427A: Swift/UVOT Detection
  6. EP250428b: Einstein Probe detection of a fast X-ray transient
  7. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  8. EP250427a: EP-FXT follow-up observations
  9. EP250427a: Lesedi optical counterpart detection
  10. EP250427A: COLIBRÍ Continuing Optical Observations
  11. GRB250427A/EP250427a GIT optical afterglow detection:
  12. EP250427a: LT optical counterpart detection
  13. GRB 250427A: Swift-XRT refined Analysis
  14. EP250427a / GRB 250427A: LCO optical counterpart detection
  15. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  16. EP250427a: REM optical/NIR afterglow detection
  17. GRB 250424A: LCO optical observation
  18. EP250427A: COLIBRÍ Optical Detection
  19. EP250427a: TRT optical counterpart detection
  20. EP250427a: Einstein Probe detection of a fast X-ray transient
  21. IceCube Alert 250426.74: Global MASTER-Net observations report
  22. GRB 250424A: SVOM/GRM observation of a long burst
  23. GRB 250424A: PRIME near-infrared detection
  24. GRB 250424A: WINTER J-band detection
  25. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  26. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  27. GRB 250419A: Mondy Optical Observations
  28. GRB 250424A: Swift/UVOT Detection
  29. Konus-Wind detection of GRB 250424A
  30. Fermi-LAT gamma-ray observations of IceCube-250421A
  31. GRB 250424A: Skynet Optical Observations
  32. GRB 250424A: Kilonova-Catcher optical afterglow detection
  33. GRB 250419a: Continued Liverpool Telescope observations
  34. GRB 250419A: SVOM/ECLAIRs refined analysis
  35. GRB 250424A: Swift-XRT refined Analysis
  36. GRB 250424A: Enhanced Swift-XRT position
  37. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  38. GRB 250424A: BlackGEM optical afterglow detection
  39. GRB 250424A: DDOTI Afterglow Detection
  40. GRB 250424A: REM optical/NIR afterglow detection
  41. GRB 250424A: Swift detection of a burst with an optical counterpart
  42. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  43. EP250421a: Nickel optical upper limit
  44. SVOM/sb25042207: XRT observations
  45. SVOM/sb25042207: BOOTES-2 early optical upper limit
  46. SVOM/sb25042207: SVOM detection of an X-ray transient
  47. IceCube-250421A: DDOTI Detection of the LAST Candidate
  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: Einstein Probe detection of an X-ray transient
  58. EP250421a: Mephisto optical counterpart confirmation
  59. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  60. EP250421a: JinShan likely optical counterpart
  61. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  62. GRB 250419A: LCO optical observation
  63. GRB 250419A: JinShan optical observations
  64. GRB 250419A: SVOM/C-GFT optical observations
  65. GRB 250419A: Swift/UVOT Follow up
  66. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  67. GRB 250419A: LCO optical afterglow multi-band observations
  68. GRB 250419A: Mondy and AbAO Optical Observations
  69. GRB 250419A: AKO Optical Afterglow Detection
  70. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  71. GRB 250419A: Swift-XRT refined Analysis
  72. GRB 250419A: KAIT optical afterglow observations
  73. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  74. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  75. GRB 250419A: SVOM detection of a soft burst
  76. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  77. EP250416a: Swift/XRT counterpart fading
  78. EP250416a: refined EP-WXT and EP-FXT analysis
  79. Konus-Wind detection of GRB 250403A
  80. EP20250416a: Swift/XRT counterpart detection
  81. IceCube-250416A: DDOTI Optical Observations
  82. EP250416a: Gemini South-GMOS optical counterpart
  83. SVOM/sb25041603 is not a GRB
  84. EP250416a: Einstein Probe detection of an X-ray transient
  85. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  86. SVOM/sb25041603: SVOM detection of an X-ray transient
  87. IceCube 250414.324: DDOTI Optical Observations
  88. EP250404a: Nanshan 0.43m Telescope optical observatios
  89. GRB 250411A: DDOTI Optical Observations
  90. GRB 250314A: e-MERLIN observations
  91. GRB 250407A: Mondy and AbAO Optical Observations
  92. EP250227a: Further NOT optical observations
  93. GRB 250320B: cubesat Avion detection
  94. IceCube-250406A: Swift-XRT observations
  95. GRB 250407A: LCO detection of a fading optical counterpart
  96. Fermi-LAT gamma-ray observations of IceCube-250406A
  97. EP250407a: Swift-XRT observations
  98. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  99. Konus-Wind detection of GRB 250407A
  100. GRB 250407A: SVOM/GRM observation of a bright long burst

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