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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"

44399 results found.

  1. GRB 250419A: Liverpool Telescope optical upper limit
  2. GRB 250407A: GRBAlpha detection
  3. GRB 250404A / EP250404a: GRBAlpha detection
  4. GRB 250330B: GRBAlpha detection
  5. GRB 250419A: SVOM/ECLAIRs refined analysis
  6. GRB 250424A: Swift-XRT refined Analysis
  7. GRB 250424A: Enhanced Swift-XRT position
  8. GRB 250424A: AstroSat CZTI detection of a bright long burst
  9. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  10. GRB 250424A: BlackGEM optical afterglow detection
  11. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  12. GRB 250424A: likely host galaxy
  13. GRB 250424A: DDOTI Afterglow Detection
  14. GRB 250424A: REM optical/NIR afterglow detection
  15. GRB 250424A: Swift detection of a burst with an optical counterpart
  16. Swift GRB 250424A: Global MASTER-Net observations report
  17. Swift GRB 250424A: Global MASTER-Net OT detection
  18. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  19. EP250421a: Nickel optical upper limit
  20. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  21. EP250421a: Upper limits from Fermi-GBM Observations
  22. SVOM/sb25042207: XRT observations
  23. SVOM/sb25042207: BOOTES-2 early optical upper limit
  24. SVOM/sb25042207: GOTO optical upper limits
  25. GRB 250421A: AstroSat CZTI detection
  26. SVOM/sb25042207: SVOM detection of an X-ray transient
  27. GRB250419A: VLA radio detection
  28. IceCube-250421A: DDOTI Detection of the LAST Candidate
  29. GRB 250419A: Mephisto Multi-band Optical Detection
  30. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  31. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  32. EP250421a: NOT optical observations
  33. GRB 250419A: Optical Observations via Virtual Telescope Project
  34. EP250421a: REM optical upper limit
  35. EP250421a: Swift/XRT counterpart detection
  36. EP250421A: COLIBRÍ Optical Upper Limit
  37. GRB 250419A: Mondy Continued Optical Observations
  38. Fermi GRB 250421A: Global MASTER-Net observations report
  39. EP250421a: Global MASTER-Net observations report
  40. GRB 250421B: AstroSat CZTI detection of a bright long burst
  41. EP250421a: Einstein Probe detection of an X-ray transient
  42. EP250421a: Mephisto optical counterpart confirmation
  43. IceCube Alert 250421.71: Global MASTER-Net observations report
  44. IceCube-250421A - IceCube observation of a high-energy neutrino candidate track-like event
  45. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  46. EP250421a: JinShan likely optical counterpart
  47. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  48. GRB 250421A: Fermi GBM Final Real-time Localization
  49. GRB 250419A: Liverpool Telescope observations
  50. GRB 250419A: LCO optical observation
  51. GRB 250419A: JinShan optical observations
  52. GRB 250419A: SVOM/VT optical continuous observations
  53. GRB 250419A: SVOM/C-GFT optical observations
  54. GRB 250419A: Swift/UVOT Follow up
  55. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  56. GRB 250419A: LCO optical afterglow multi-band observations
  57. GRB 250419A: Mondy and AbAO Optical Observations
  58. GRB 250419A: Liverpool Telescope observations
  59. GRB 250419A: AKO Optical Afterglow Detection
  60. GRB 250419A: MASTER optical afterglow observation
  61. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  62. GRB 250407A: rest-frame energetics from Konus-Wind observation
  63. GRB 250419A: Swift-XRT localisation
  64. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  65. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  66. GRB 250419A: Swift-XRT refined Analysis
  67. GRB 250419A: GOTO optical counterpart detection
  68. GRB 250419A: KAIT optical afterglow observations
  69. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  70. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  71. GRB 250419A: SVOM detection of a soft burst
  72. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  73. EP250416a: Swift/XRT counterpart fading
  74. EP250416a: refined EP-WXT and EP-FXT analysis
  75. Konus-Wind detection of GRB 250403A
  76. EP20250416a: Swift/XRT counterpart detection
  77. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  78. IceCube-250416A: DDOTI Optical Observations
  79. EP250416a: Gemini South-GMOS optical counterpart
  80. EP250225a: SVOM/VT optical brightening
  81. SVOM/sb25041603 is not a GRB
  82. EP250416a: GSP optical upper limit
  83. EP250416a: Global MASTER-Net observations report
  84. Fermi Gamma-ray Burst Monitor trigger 766505186/250416588 (GRB 250416A) is not a GRB
  85. EP250416a: Einstein Probe detection of an X-ray transient
  86. IceCube-250416A - IceCube observation of a high-energy neutrino candidate track-like event
  87. IceCube-250416A: Global MASTER-Net observations report
  88. Fermi Gamma-ray Burst Monitor trigger 766511207/250416657 is not a GRB
  89. GRB 250416B: Fermi GBM Final Real-time Localization
  90. GRB 250416A: Fermi GBM Final Real-time Localization
  91. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  92. SVOM/sb25041603: SVOM detection of an X-ray transient
  93. Fermi Gamma-ray Burst Monitor trigger 766474855/250416237 is not a GRB
  94. IceCube 250414.324: DDOTI Optical Observations
  95. GRB 250413A: AstroSat CZTI detection
  96. EP250304a: ATCA radio observations
  97. GRB 250412A: AstroSat CZTI detection
  98. EP250404a: Nanshan 0.43m Telescope optical observatios
  99. Fermi trigger No 766148493: Global MASTER-Net observations report
  100. Fermi trigger No 766173972: Global MASTER-Net observations report

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