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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"

32509 results found.

  1. EP250427a: LT optical counterpart detection
  2. GRB 250427A: Swift-XRT refined Analysis
  3. EP250427a / GRB 250427A: LCO optical counterpart detection
  4. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  5. EP250427A/GRB250427A: Keck/LRIS redshift
  6. EP250427a: REM optical/NIR afterglow detection
  7. GRB 250424A: LCO optical observation
  8. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  9. EP250427A: COLIBRÍ Optical Detection
  10. EP250427a: TRT optical counterpart detection
  11. EP250427a: Global MASTER-Net observations report
  12. EP250427a: Einstein Probe detection of a fast X-ray transient
  13. GRB 250424A: Swift-BAT refined analysis
  14. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event (duplicate submission)
  15. GRB 250424A: SVOM/GRM observation of a long burst
  16. GRB 250424A: PRIME near-infrared detection
  17. GRB 250424A: WINTER J-band detection
  18. GRB 250424A: EIRSAT-1 GMOD Detection
  19. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  20. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  21. GRB 250424A: SVOM/VT optical observation
  22. GRB 250419A: Mondy Optical Observations
  23. GRB 250424A: Swift/UVOT Detection
  24. Konus-Wind detection of GRB 250424A
  25. Fermi-LAT gamma-ray observations of IceCube-250421A
  26. GRB 250424A: Skynet Optical Observations
  27. GRB 250424A: Kilonova-Catcher optical afterglow detection
  28. GRB 250419a: Continued Liverpool Telescope observations
  29. GRB 250419A: Liverpool Telescope optical upper limit
  30. GRB 250407A: GRBAlpha detection
  31. GRB 250404A / EP250404a: GRBAlpha detection
  32. GRB 250330B: GRBAlpha detection
  33. GRB 250419A: SVOM/ECLAIRs refined analysis
  34. GRB 250424A: AstroSat CZTI detection of a bright long burst
  35. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  36. GRB 250424A: BlackGEM optical afterglow detection
  37. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  38. GRB 250424A: likely host galaxy
  39. GRB 250424A: DDOTI Afterglow Detection
  40. GRB 250424A: REM optical/NIR afterglow detection
  41. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  42. EP250421a: Nickel optical upper limit
  43. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  44. EP250421a: Upper limits from Fermi-GBM Observations
  45. SVOM/sb25042207: XRT observations
  46. SVOM/sb25042207: BOOTES-2 early optical upper limit
  47. SVOM/sb25042207: GOTO optical upper limits
  48. GRB 250421A: AstroSat CZTI detection
  49. GRB250419A: VLA radio detection
  50. IceCube-250421A: DDOTI Detection of the LAST Candidate
  51. GRB 250419A: Mephisto Multi-band Optical Detection
  52. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  53. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  54. EP250421a: NOT optical observations
  55. GRB 250419A: Optical Observations via Virtual Telescope Project
  56. EP250421a: REM optical upper limit
  57. EP250421a: Swift/XRT counterpart detection
  58. EP250421A: COLIBRÍ Optical Upper Limit
  59. GRB 250419A: Mondy Continued Optical Observations
  60. Fermi GRB 250421A: Global MASTER-Net observations report
  61. EP250421a: Global MASTER-Net observations report
  62. EP250421a: Mephisto optical counterpart confirmation
  63. GRB 250419A: Liverpool Telescope observations
  64. GRB 250419A: LCO optical observation
  65. GRB 250419A: JinShan optical observations
  66. GRB 250419A: SVOM/VT optical continuous observations
  67. GRB 250419A: SVOM/C-GFT optical observations
  68. GRB 250419A: Swift/UVOT Follow up
  69. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  70. GRB 250419A: LCO optical afterglow multi-band observations
  71. GRB 250419A: Mondy and AbAO Optical Observations
  72. GRB 250419A: Liverpool Telescope observations
  73. GRB 250419A: AKO Optical Afterglow Detection
  74. GRB 250419A: MASTER optical afterglow observation
  75. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  76. GRB 250407A: rest-frame energetics from Konus-Wind observation
  77. GRB 250419A: Swift-XRT localisation
  78. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  79. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  80. GRB 250419A: Swift-XRT refined Analysis
  81. GRB 250419A: GOTO optical counterpart detection
  82. GRB 250419A: KAIT optical afterglow observations
  83. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  84. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  85. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  86. EP250416a: Swift/XRT counterpart fading
  87. EP250416a: refined EP-WXT and EP-FXT analysis
  88. Konus-Wind detection of GRB 250403A
  89. EP20250416a: Swift/XRT counterpart detection
  90. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  91. IceCube-250416A: DDOTI Optical Observations
  92. EP250416a: Gemini South-GMOS optical counterpart
  93. EP250225a: SVOM/VT optical brightening
  94. SVOM/sb25041603 is not a GRB
  95. EP250416a: GSP optical upper limit
  96. EP250416a: Global MASTER-Net observations report
  97. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  98. GRB 250413A: AstroSat CZTI detection
  99. EP250304a: ATCA radio observations
  100. EP250404a: Nanshan 0.43m Telescope optical observatios

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