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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"

35434 results found.

  1. GRB 250419A: MASTER optical afterglow observation
  2. GRB 250407A: rest-frame energetics from Konus-Wind observation
  3. GRB 250419A: Swift-XRT localisation
  4. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  5. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  6. GRB 250419A: Swift-XRT refined Analysis
  7. GRB 250419A: GOTO optical counterpart detection
  8. GRB 250419A: KAIT optical afterglow observations
  9. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  10. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  11. GRB 250419A: SVOM detection of a soft burst
  12. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  13. Konus-Wind detection of GRB 250403A
  14. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  15. SVOM/sb25041603 is not a GRB
  16. Fermi Gamma-ray Burst Monitor trigger 766505186/250416588 (GRB 250416A) is not a GRB
  17. Fermi Gamma-ray Burst Monitor trigger 766511207/250416657 is not a GRB
  18. GRB 250416B: Fermi GBM Final Real-time Localization
  19. GRB 250416A: Fermi GBM Final Real-time Localization
  20. Fermi Gamma-ray Burst Monitor trigger 766474855/250416237 is not a GRB
  21. GRB 250413A: AstroSat CZTI detection
  22. EP250304a: ATCA radio observations
  23. GRB 250412A: AstroSat CZTI detection
  24. GRB 250411A: DDOTI Optical Observations
  25. Fermi GRB 250411A: Global MASTER-Net observations report
  26. GRB 250411A: Fermi GBM Final Real-time Localization
  27. GRB 250407A: Continued KAIT/Nickel optical observations
  28. GRB 250314A: e-MERLIN observations
  29. GRB 250407A: Mondy and AbAO Optical Observations
  30. GRB 250320B: cubesat Avion detection
  31. IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
  32. IPN triangulation of GRB 250407A
  33. GRB 250407A: LCO detection of a fading optical counterpart
  34. EP250407a: Swift-XRT observations
  35. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  36. Konus-Wind detection of GRB 250407A
  37. GRB 250407A: SVOM/GRM observation of a bright long burst
  38. GRB 250407A: EP-WXT afterglow detection
  39. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  40. GRB 250407A: KAIT Optical Afterglow Candidate
  41. GRB 250407A: Fermi GBM Detection
  42. GRB 250407A: Swift-XRT afterglow detection
  43. Fermi GRB 250407A: Global MASTER-Net observations report
  44. GRB 250407A: Swift ToO observations
  45. GRB 250407A: SRG/ART-XC afterglow detection
  46. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  47. Konus-Wind detection of GRB 250406B (short/hard)
  48. IPN triangulation of GRB 250406B (short/hard)
  49. GRB 250407A: BALROG localization (Fermi Trigger 765733706 / GRB 250407659)
  50. GRB 250407A: Fermi GBM Final Real-time Localization
  51. GRB 250406A: AstroSat CZTI detection
  52. Fermi GRB 250406A: Global MASTER-Net observations report
  53. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  54. GRB 250406A: Fermi GBM Final Real-time Localization
  55. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  56. Fermi Gamma-ray Burst Monitor trigger 765619921/250406342 is not a GRB
  57. GRB 250404A / EP250404a: RC500 INASAN-Kislovodsk optical upper limit
  58. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  59. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  60. Konus-Wind detection of GRB 250404A / EP250404a
  61. GRB 250404A / EP250404a: Mondy optical observations
  62. GRB 250404A / EP250404a: GMG spectroscopic redshift at z ~ 2.627
  63. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  64. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  65. GRB 250404A / EP250404a: NOT optical observations
  66. GRB 250331D: Swift-XRT afterglow detection
  67. GRB 250404B: AstroSat CZTI detection of a short burst
  68. GRB 250403A: AstroSat CZTI detection
  69. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  70. EP250404a: REM optical/NIR observations
  71. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  72. EP250404a: LCO optical counterpart detection
  73. Fermi GRB 250404A: Global MASTER-Net observations report
  74. GRB 250403A: Montarrenti Observatory optical detection
  75. GRB 250404A: Fermi GBM Detection
  76. GRB 250403A: KAIT optical observations
  77. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  78. EP250404a: Xinglong-2.16m spectroscopic redshift
  79. GRB 250403A: Fermi GBM observations
  80. GRB 250327B: VIRT Optical Upper Limit
  81. GRB 250331C Swift-BAT refined analysis
  82. GRB 250331B Swift-BAT refined analysis
  83. GRB 250330A Swift-BAT refined analysis
  84. EP250404a: BOOTES-4/JGT optical afterglow detection
  85. EP250404a: Nanshan/HMT optical counterpart detection
  86. EP250404a: Einstein Probe detection of an X-ray transient
  87. GRB 250404A: Fermi GBM Final Real-time Localization
  88. GRB 250402A: Mondy optical observations
  89. GRB 250403A: Swift/UVOT Detection
  90. GRB 250402A: Swift/UVOT Upper Limits
  91. GRB 250403A: SVOM/VT optical observation
  92. GRB 250403A: REM NIR afterglow detection
  93. GRB 250403A: LCO optical counterpart detection
  94. GRB 250403A: JinShan optical observations
  95. GRB 250402A: EP-FXT afterglow detection
  96. GRB 250403A: Optical counterpart detection by LCO.
  97. GRB 250403A: Swift-XRT observations
  98. GRB 250322A: 10 GHz VLA radio upper limits
  99. Fermi GRB 250403A: Global MASTER-Net observations report
  100. GRB 250403A: GOTO optical counterpart follow-up observations

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