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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"

23211 results found.

  1. EP250427a/GRB250427A: HCT optical follow-up
  2. SVOM/sb25043004: SVOM detection of a X-ray transient
  3. EP250428b: refined analysis of the EP-FXT follow-up observation
  4. EP250428b: GROWTH-India telescope optical upper limit
  5. EP250428b: SAO RAS optical upper limit
  6. EP250428b: LAST optical upper limit
  7. GRB 250427A: Swift/UVOT Detection
  8. EP250428b: Einstein Probe detection of a fast X-ray transient
  9. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  10. EP250427a: EP-FXT follow-up observations
  11. EP250427a: Lesedi optical counterpart detection
  12. EP250427A: COLIBRÍ Continuing Optical Observations
  13. GRB250427A/EP250427a GIT optical afterglow detection:
  14. EP250427a: LT optical counterpart detection
  15. GRB 250427A: Swift-XRT refined Analysis
  16. EP250427a / GRB 250427A: LCO optical counterpart detection
  17. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  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. EP250427a: Einstein Probe detection of a fast X-ray transient
  23. IceCube Alert 250426.74: Global MASTER-Net observations report
  24. GRB 250424A: SVOM/GRM observation of a long burst
  25. GRB 250424A: PRIME near-infrared detection
  26. GRB 250424A: WINTER J-band detection
  27. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  28. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  29. GRB 250419A: Mondy Optical Observations
  30. GRB 250424A: Swift/UVOT Detection
  31. Konus-Wind detection of GRB 250424A
  32. Fermi-LAT gamma-ray observations of IceCube-250421A
  33. GRB 250424A: Skynet Optical Observations
  34. GRB 250424A: Kilonova-Catcher optical afterglow detection
  35. GRB 250419a: Continued Liverpool Telescope observations
  36. GRB 250419A: SVOM/ECLAIRs refined analysis
  37. GRB 250424A: Swift-XRT refined Analysis
  38. GRB 250424A: Enhanced Swift-XRT position
  39. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  40. GRB 250424A: BlackGEM optical afterglow detection
  41. GRB 250424A: DDOTI Afterglow Detection
  42. GRB 250424A: REM optical/NIR afterglow detection
  43. GRB 250424A: Swift detection of a burst with an optical counterpart
  44. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  45. EP250421a: Nickel optical upper limit
  46. SVOM/sb25042207: XRT observations
  47. SVOM/sb25042207: BOOTES-2 early optical upper limit
  48. SVOM/sb25042207: SVOM detection of an X-ray transient
  49. IceCube-250421A: DDOTI Detection of the LAST Candidate
  50. GRB 250419A: Mephisto Multi-band Optical Detection
  51. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  52. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  53. EP250421a: NOT optical observations
  54. GRB 250419A: Optical Observations via Virtual Telescope Project
  55. EP250421a: REM optical upper limit
  56. EP250421a: Swift/XRT counterpart detection
  57. EP250421A: COLIBRÍ Optical Upper Limit
  58. GRB 250419A: Mondy Continued Optical Observations
  59. EP250421a: Einstein Probe detection of an X-ray transient
  60. EP250421a: Mephisto optical counterpart confirmation
  61. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  62. EP250421a: JinShan likely optical counterpart
  63. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  64. GRB 250419A: LCO optical observation
  65. GRB 250419A: JinShan optical observations
  66. GRB 250419A: SVOM/C-GFT optical observations
  67. GRB 250419A: Swift/UVOT Follow up
  68. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  69. GRB 250419A: LCO optical afterglow multi-band observations
  70. GRB 250419A: Mondy and AbAO Optical Observations
  71. GRB 250419A: AKO Optical Afterglow Detection
  72. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  73. GRB 250419A: Swift-XRT refined Analysis
  74. GRB 250419A: KAIT optical afterglow observations
  75. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  76. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  77. GRB 250419A: SVOM detection of a soft burst
  78. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  79. EP250416a: Swift/XRT counterpart fading
  80. EP250416a: refined EP-WXT and EP-FXT analysis
  81. Konus-Wind detection of GRB 250403A
  82. EP20250416a: Swift/XRT counterpart detection
  83. IceCube-250416A: DDOTI Optical Observations
  84. EP250416a: Gemini South-GMOS optical counterpart
  85. SVOM/sb25041603 is not a GRB
  86. EP250416a: Einstein Probe detection of an X-ray transient
  87. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  88. SVOM/sb25041603: SVOM detection of an X-ray transient
  89. IceCube 250414.324: DDOTI Optical Observations
  90. EP250404a: Nanshan 0.43m Telescope optical observatios
  91. GRB 250411A: DDOTI Optical Observations
  92. GRB 250314A: e-MERLIN observations
  93. GRB 250407A: Mondy and AbAO Optical Observations
  94. EP250227a: Further NOT optical observations
  95. GRB 250320B: cubesat Avion detection
  96. IceCube-250406A: Swift-XRT observations
  97. GRB 250407A: LCO detection of a fading optical counterpart
  98. Fermi-LAT gamma-ray observations of IceCube-250406A
  99. EP250407a: Swift-XRT observations
  100. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube

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