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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.

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

32408 results found.

  1. GRB 250424A: AstroSat CZTI detection of a bright long burst
  2. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  3. GRB 250424A: BlackGEM optical afterglow detection
  4. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  5. GRB 250424A: likely host galaxy
  6. GRB 250424A: DDOTI Afterglow Detection
  7. GRB 250424A: REM optical/NIR afterglow detection
  8. GRB 250424A: Swift detection of a burst with an optical counterpart
  9. Swift GRB 250424A: Global MASTER-Net observations report
  10. Swift GRB 250424A: Global MASTER-Net OT detection
  11. EP250421a: Nickel optical upper limit
  12. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  13. EP250421a: Upper limits from Fermi-GBM Observations
  14. SVOM/sb25042207: GOTO optical upper limits
  15. GRB 250421A: AstroSat CZTI detection
  16. GRB250419A: VLA radio detection
  17. GRB 250419A: Mephisto Multi-band Optical Detection
  18. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  19. GRB 250419A: Optical Observations via Virtual Telescope Project
  20. GRB 250419A: Mondy Continued Optical Observations
  21. Fermi GRB 250421A: Global MASTER-Net observations report
  22. GRB 250421B: AstroSat CZTI detection of a bright long burst
  23. GRB 250421A: Fermi GBM Final Real-time Localization
  24. GRB 250419A: Liverpool Telescope observations
  25. GRB 250419A: LCO optical observation
  26. GRB 250419A: JinShan optical observations
  27. GRB 250419A: SVOM/VT optical continuous observations
  28. GRB 250419A: SVOM/C-GFT optical observations
  29. GRB 250419A: Swift/UVOT Follow up
  30. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  31. GRB 250419A: LCO optical afterglow multi-band observations
  32. GRB 250419A: Mondy and AbAO Optical Observations
  33. GRB 250419A: Liverpool Telescope observations
  34. GRB 250419A: AKO Optical Afterglow Detection
  35. GRB 250419A: MASTER optical afterglow observation
  36. GRB 250407A: rest-frame energetics from Konus-Wind observation
  37. GRB 250419A: Swift-XRT localisation
  38. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  39. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  40. GRB 250419A: Swift-XRT refined Analysis
  41. GRB 250419A: GOTO optical counterpart detection
  42. GRB 250419A: KAIT optical afterglow observations
  43. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  44. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  45. GRB 250419A: SVOM detection of a soft burst
  46. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  47. Konus-Wind detection of GRB 250403A
  48. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  49. SVOM/sb25041603 is not a GRB
  50. Fermi Gamma-ray Burst Monitor trigger 766505186/250416588 (GRB 250416A) is not a GRB
  51. Fermi Gamma-ray Burst Monitor trigger 766511207/250416657 is not a GRB
  52. GRB 250416B: Fermi GBM Final Real-time Localization
  53. GRB 250416A: Fermi GBM Final Real-time Localization
  54. Fermi Gamma-ray Burst Monitor trigger 766474855/250416237 is not a GRB
  55. GRB 250413A: AstroSat CZTI detection
  56. EP250304a: ATCA radio observations
  57. GRB 250412A: AstroSat CZTI detection
  58. GRB 250411A: DDOTI Optical Observations
  59. Fermi GRB 250411A: Global MASTER-Net observations report
  60. GRB 250411A: Fermi GBM Final Real-time Localization
  61. GRB 250407A: Continued KAIT/Nickel optical observations
  62. GRB 250314A: e-MERLIN observations
  63. GRB 250407A: Mondy and AbAO Optical Observations
  64. GRB 250320B: cubesat Avion detection
  65. IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
  66. IPN triangulation of GRB 250407A
  67. GRB 250407A: LCO detection of a fading optical counterpart
  68. EP250407a: Swift-XRT observations
  69. Konus-Wind detection of GRB 250407A
  70. GRB 250407A: SVOM/GRM observation of a bright long burst
  71. GRB 250407A: EP-WXT afterglow detection
  72. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  73. GRB 250407A: KAIT Optical Afterglow Candidate
  74. GRB 250407A: Fermi GBM Detection
  75. GRB 250407A: Swift-XRT afterglow detection
  76. Fermi GRB 250407A: Global MASTER-Net observations report
  77. GRB 250407A: Swift ToO observations
  78. GRB 250407A: SRG/ART-XC afterglow detection
  79. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  80. Konus-Wind detection of GRB 250406B (short/hard)
  81. IPN triangulation of GRB 250406B (short/hard)
  82. GRB 250407A: BALROG localization (Fermi Trigger 765733706 / GRB 250407659)
  83. GRB 250407A: Fermi GBM Final Real-time Localization
  84. GRB 250406A: AstroSat CZTI detection
  85. Fermi GRB 250406A: Global MASTER-Net observations report
  86. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  87. GRB 250406A: Fermi GBM Final Real-time Localization
  88. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  89. Fermi Gamma-ray Burst Monitor trigger 765619921/250406342 is not a GRB
  90. GRB 250404A / EP250404a: RC500 INASAN-Kislovodsk optical upper limit
  91. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  92. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  93. Konus-Wind detection of GRB 250404A / EP250404a
  94. GRB 250404A / EP250404a: Mondy optical observations
  95. GRB 250404A / EP250404a: GMG spectroscopic redshift at z ~ 2.627
  96. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  97. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  98. GRB 250404A / EP250404a: NOT optical observations
  99. GRB 250331D: Swift-XRT afterglow detection
  100. GRB 250404B: AstroSat CZTI detection of a short burst

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