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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"

35447 results found.

  1. Fermi GRB 250421A: Global MASTER-Net observations report
  2. GRB 250421B: AstroSat CZTI detection of a bright long burst
  3. GRB 250421A: Fermi GBM Final Real-time Localization
  4. GRB 250419A: Liverpool Telescope observations
  5. GRB 250419A: LCO optical observation
  6. GRB 250419A: JinShan optical observations
  7. GRB 250419A: SVOM/VT optical continuous observations
  8. GRB 250419A: SVOM/C-GFT optical observations
  9. GRB 250419A: Swift/UVOT Follow up
  10. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  11. GRB 250419A: LCO optical afterglow multi-band observations
  12. GRB 250419A: Mondy and AbAO Optical Observations
  13. GRB 250419A: Liverpool Telescope observations
  14. GRB 250419A: AKO Optical Afterglow Detection
  15. GRB 250419A: MASTER optical afterglow observation
  16. GRB 250407A: rest-frame energetics from Konus-Wind observation
  17. GRB 250419A: Swift-XRT localisation
  18. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  19. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  20. GRB 250419A: Swift-XRT refined Analysis
  21. GRB 250419A: GOTO optical counterpart detection
  22. GRB 250419A: KAIT optical afterglow observations
  23. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  24. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  25. GRB 250419A: SVOM detection of a soft burst
  26. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  27. Konus-Wind detection of GRB 250403A
  28. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  29. SVOM/sb25041603 is not a GRB
  30. Fermi Gamma-ray Burst Monitor trigger 766505186/250416588 (GRB 250416A) is not a GRB
  31. Fermi Gamma-ray Burst Monitor trigger 766511207/250416657 is not a GRB
  32. GRB 250416B: Fermi GBM Final Real-time Localization
  33. GRB 250416A: Fermi GBM Final Real-time Localization
  34. Fermi Gamma-ray Burst Monitor trigger 766474855/250416237 is not a GRB
  35. GRB 250413A: AstroSat CZTI detection
  36. EP250304a: ATCA radio observations
  37. GRB 250412A: AstroSat CZTI detection
  38. GRB 250411A: DDOTI Optical Observations
  39. Fermi GRB 250411A: Global MASTER-Net observations report
  40. GRB 250411A: Fermi GBM Final Real-time Localization
  41. GRB 250407A: Continued KAIT/Nickel optical observations
  42. GRB 250314A: e-MERLIN observations
  43. GRB 250407A: Mondy and AbAO Optical Observations
  44. GRB 250320B: cubesat Avion detection
  45. IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
  46. IPN triangulation of GRB 250407A
  47. GRB 250407A: LCO detection of a fading optical counterpart
  48. EP250407a: Swift-XRT observations
  49. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  50. Konus-Wind detection of GRB 250407A
  51. GRB 250407A: SVOM/GRM observation of a bright long burst
  52. GRB 250407A: EP-WXT afterglow detection
  53. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  54. GRB 250407A: KAIT Optical Afterglow Candidate
  55. GRB 250407A: Fermi GBM Detection
  56. GRB 250407A: Swift-XRT afterglow detection
  57. Fermi GRB 250407A: Global MASTER-Net observations report
  58. GRB 250407A: Swift ToO observations
  59. GRB 250407A: SRG/ART-XC afterglow detection
  60. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  61. Konus-Wind detection of GRB 250406B (short/hard)
  62. IPN triangulation of GRB 250406B (short/hard)
  63. GRB 250407A: BALROG localization (Fermi Trigger 765733706 / GRB 250407659)
  64. GRB 250407A: Fermi GBM Final Real-time Localization
  65. GRB 250406A: AstroSat CZTI detection
  66. Fermi GRB 250406A: Global MASTER-Net observations report
  67. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  68. GRB 250406A: Fermi GBM Final Real-time Localization
  69. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  70. Fermi Gamma-ray Burst Monitor trigger 765619921/250406342 is not a GRB
  71. GRB 250404A / EP250404a: RC500 INASAN-Kislovodsk optical upper limit
  72. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  73. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  74. Konus-Wind detection of GRB 250404A / EP250404a
  75. GRB 250404A / EP250404a: Mondy optical observations
  76. GRB 250404A / EP250404a: GMG spectroscopic redshift at z ~ 2.627
  77. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  78. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  79. GRB 250404A / EP250404a: NOT optical observations
  80. GRB 250331D: Swift-XRT afterglow detection
  81. GRB 250404B: AstroSat CZTI detection of a short burst
  82. GRB 250403A: AstroSat CZTI detection
  83. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  84. EP250404a: REM optical/NIR observations
  85. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  86. EP250404a: LCO optical counterpart detection
  87. Fermi GRB 250404A: Global MASTER-Net observations report
  88. GRB 250403A: Montarrenti Observatory optical detection
  89. GRB 250404A: Fermi GBM Detection
  90. GRB 250403A: KAIT optical observations
  91. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  92. EP250404a: Xinglong-2.16m spectroscopic redshift
  93. GRB 250403A: Fermi GBM observations
  94. GRB 250327B: VIRT Optical Upper Limit
  95. GRB 250331C Swift-BAT refined analysis
  96. GRB 250331B Swift-BAT refined analysis
  97. GRB 250330A Swift-BAT refined analysis
  98. EP250404a: BOOTES-4/JGT optical afterglow detection
  99. EP250404a: Nanshan/HMT optical counterpart detection
  100. EP250404a: Einstein Probe detection of an X-ray transient

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