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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"

35324 results found.

  1. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  2. GRB 250419A: SVOM detection of a soft burst
  3. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  4. Konus-Wind detection of GRB 250403A
  5. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  6. SVOM/sb25041603 is not a GRB
  7. Fermi Gamma-ray Burst Monitor trigger 766505186/250416588 (GRB 250416A) is not a GRB
  8. Fermi Gamma-ray Burst Monitor trigger 766511207/250416657 is not a GRB
  9. GRB 250416B: Fermi GBM Final Real-time Localization
  10. GRB 250416A: Fermi GBM Final Real-time Localization
  11. Fermi Gamma-ray Burst Monitor trigger 766474855/250416237 is not a GRB
  12. GRB 250413A: AstroSat CZTI detection
  13. EP250304a: ATCA radio observations
  14. GRB 250412A: AstroSat CZTI detection
  15. GRB 250411A: DDOTI Optical Observations
  16. Fermi GRB 250411A: Global MASTER-Net observations report
  17. GRB 250411A: Fermi GBM Final Real-time Localization
  18. GRB 250407A: Continued KAIT/Nickel optical observations
  19. GRB 250314A: e-MERLIN observations
  20. GRB 250407A: Mondy and AbAO Optical Observations
  21. GRB 250320B: cubesat Avion detection
  22. IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
  23. IPN triangulation of GRB 250407A
  24. GRB 250407A: LCO detection of a fading optical counterpart
  25. EP250407a: Swift-XRT observations
  26. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  27. Konus-Wind detection of GRB 250407A
  28. GRB 250407A: SVOM/GRM observation of a bright long burst
  29. GRB 250407A: EP-WXT afterglow detection
  30. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  31. GRB 250407A: KAIT Optical Afterglow Candidate
  32. GRB 250407A: Fermi GBM Detection
  33. GRB 250407A: Swift-XRT afterglow detection
  34. Fermi GRB 250407A: Global MASTER-Net observations report
  35. GRB 250407A: Swift ToO observations
  36. GRB 250407A: SRG/ART-XC afterglow detection
  37. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  38. Konus-Wind detection of GRB 250406B (short/hard)
  39. IPN triangulation of GRB 250406B (short/hard)
  40. GRB 250407A: BALROG localization (Fermi Trigger 765733706 / GRB 250407659)
  41. GRB 250407A: Fermi GBM Final Real-time Localization
  42. GRB 250406A: AstroSat CZTI detection
  43. Fermi GRB 250406A: Global MASTER-Net observations report
  44. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  45. GRB 250406A: Fermi GBM Final Real-time Localization
  46. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  47. Fermi Gamma-ray Burst Monitor trigger 765619921/250406342 is not a GRB
  48. GRB 250404A / EP250404a: RC500 INASAN-Kislovodsk optical upper limit
  49. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  50. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  51. Konus-Wind detection of GRB 250404A / EP250404a
  52. GRB 250404A / EP250404a: Mondy optical observations
  53. GRB 250404A / EP250404a: GMG spectroscopic redshift at z ~ 2.627
  54. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  55. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  56. GRB 250404A / EP250404a: NOT optical observations
  57. GRB 250331D: Swift-XRT afterglow detection
  58. GRB 250404B: AstroSat CZTI detection of a short burst
  59. GRB 250403A: AstroSat CZTI detection
  60. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  61. EP250404a: REM optical/NIR observations
  62. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  63. EP250404a: LCO optical counterpart detection
  64. Fermi GRB 250404A: Global MASTER-Net observations report
  65. GRB 250403A: Montarrenti Observatory optical detection
  66. GRB 250404A: Fermi GBM Detection
  67. GRB 250403A: KAIT optical observations
  68. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  69. EP250404a: Xinglong-2.16m spectroscopic redshift
  70. GRB 250403A: Fermi GBM observations
  71. GRB 250327B: VIRT Optical Upper Limit
  72. GRB 250331C Swift-BAT refined analysis
  73. GRB 250331B Swift-BAT refined analysis
  74. GRB 250330A Swift-BAT refined analysis
  75. EP250404a: BOOTES-4/JGT optical afterglow detection
  76. EP250404a: Nanshan/HMT optical counterpart detection
  77. EP250404a: Einstein Probe detection of an X-ray transient
  78. GRB 250404A: Fermi GBM Final Real-time Localization
  79. GRB 250402A: Mondy optical observations
  80. GRB 250403A: Swift/UVOT Detection
  81. GRB 250402A: Swift/UVOT Upper Limits
  82. GRB 250403A: SVOM/VT optical observation
  83. GRB 250403A: REM NIR afterglow detection
  84. GRB 250403A: LCO optical counterpart detection
  85. GRB 250403A: JinShan optical observations
  86. GRB 250402A: EP-FXT afterglow detection
  87. GRB 250403A: Optical counterpart detection by LCO.
  88. GRB 250403A: Swift-XRT observations
  89. GRB 250322A: 10 GHz VLA radio upper limits
  90. Fermi GRB 250403A: Global MASTER-Net observations report
  91. GRB 250403A: GOTO optical counterpart follow-up observations
  92. GRB 250402A: NUTTelA-TAO Early Optical Limits
  93. GRB 250403A: GMG Optical Observation
  94. GRB 250403A: 1.6m Mephisto multi-band optical detection
  95. GRB 250402A: Fermi GBM Observation
  96. GRB 250403A: SVOM/C-GFT optical observations
  97. GRB 250403A: GOTO detection of the optical afterglow
  98. GRB 250402A: Swift-XRT observations
  99. GRB 250403A : SVOM detection of a burst
  100. GRB 250403A: Fermi GBM Final Real-time Localization

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