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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"

5822 results found.

  1. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  2. GRB 250702A: Fermi GBM Detection
  3. GRB 250702D: Fermi GBM Final Localization Correction
  4. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  5. GRB 250702A: Fermi GBM Final Real-time Localization
  6. Fermi Gamma-ray Burst Monitor trigger 772981768/250630548 is not a GRB
  7. Fermi GRB 250626A: Global MASTER-Net observations report
  8. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  9. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  10. GRB 250625A: ABObservatory afterglow detection
  11. GRB 250521A: VZLUSAT-2 detection
  12. Fermi trigger No 772190032: Global MASTER-Net observations report
  13. GRB 250620C: Fermi GBM Final Real-time Localization
  14. Fermi trigger No 772128434: Global MASTER-Net observations report
  15. GRB 250617B: Nickel telescope optical observations
  16. GRB 250617B: COLIBRÍ optical observations
  17. GRB 250617B: NUTTelA-TAO early time optical observations
  18. GRB 250617A: Fermi GBM Final Real-time Localization
  19. EP#01709178975: Swift-XRT counterpart detection
  20. GRB 250615A: DDOTI Optical Upper Limit
  21. Fermi trigger No 771752663: Global MASTER-Net observations report
  22. IceCube alert 141029_8144692 retraction
  23. EP250610a: Global MASTER-Net observations report
  24. EP250610a: REM optical/NIR observations
  25. GRB 250609A: Fermi GBM Observation
  26. Fermi trigger No 771072240: Global MASTER-Net observations report
  27. The EP-WXT trigger 01709178283 is likely a flaring star
  28. Fermi trigger No 770867684: Global MASTER-Net observations report
  29. Fermi GRB 250601A: Global MASTER-Net observations report
  30. EP#01709177494: SVOM/VT optical observations
  31. GRB 250530C: BOOTES-7 optical upper limit
  32. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  33. Fermi trigger No 770047117: Global MASTER-Net observations report
  34. Fermi trigger No 769611916: Global MASTER-Net observations report
  35. Fermi GRB 250522B: Global MASTER-Net observations report
  36. Fermi GRB 250521D: Global MASTER-Net observations report
  37. GRB 250521D: DDOTI Optical Upper Limit
  38. GRB 250520A: 10 GHz VLA radio source
  39. GRB 250516A: COLIBRÍ optical upper limit
  40. Fermi GRB 250516A: Global MASTER-Net observations report
  41. Fermi GRB 250512A: Global MASTER-Net observations report
  42. GRB 250507B: AstroSat CZTI detection
  43. EP250512a: Global MASTER-Net observations report
  44. GRB 250507B: GRBAlpha detection
  45. EP250511a: COLIBRÍ optical counterpart candidate
  46. EP250511a: BOOTES-5 optical upper limit
  47. Fermi GRB 250510C: Global MASTER-Net observations report
  48. GRB 250509A: Fermi GBM Observation
  49. Fermi GRB 250509A: Global MASTER-Net observations report
  50. Swift GRB 250509A: Global MASTER-Net observations report
  51. GRB 250509A: Swift detection of a burst
  52. Fermi-LAT Gamma-ray Observations of IceCube-250506A
  53. IceCube Alert 250506.59: Global MASTER-Net observations report
  54. GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
  55. GRB 250504A: REM optical/NIR observations
  56. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  57. Fermi trigger No 767623859: Global MASTER-Net observations report
  58. EP250427A: COLIBRÍ Continuing Optical Observations
  59. EP250427A: COLIBRÍ Optical Detection
  60. EP 250427a: BOOTES-7 optical afterglow candidate
  61. EP250427a: Global MASTER-Net observations report
  62. GRB 250424A: SVOM/VT optical observation
  63. Fermi-LAT gamma-ray observations of IceCube-250421A
  64. GRB 250424A: BlackGEM optical afterglow detection
  65. IceCube Alert 250421.71: Global MASTER-Net observations report
  66. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  67. EP250225a: SVOM/VT optical brightening
  68. IceCube 250414.324: DDOTI Optical Observations
  69. Fermi trigger No 766148493: Global MASTER-Net observations report
  70. Fermi trigger No 766173972: Global MASTER-Net observations report
  71. GRB 250411A: Fermi GBM Final Real-time Localization
  72. GRB 250407A: Continued KAIT/Nickel optical observations
  73. GRB 250407A: Mondy and AbAO Optical Observations
  74. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A
  75. IPN triangulation of GRB 250407A
  76. Fermi GRB 250407A: Global MASTER-Net observations report
  77. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  78. Fermi trigger No 765619921: Global MASTER-Net observations report
  79. GRB 250404A / EP250404a: Mondy optical observations
  80. GRB 250404A / EP250404a: NOT optical observations
  81. Fermi GRB 250404A: Global MASTER-Net observations report
  82. EP250404a: Global MASTER-Net observations report
  83. GRB 250402B: AstroSat CZTI detection of a short burst
  84. Fermi GRB 250331E: Global MASTER-Net observations report
  85. LIGO/Virgo/KAGRA S250331o: NED Galaxies in the 3-Initial Localization Volume
  86. GRB 250331C: Swift detection of a burst
  87. GRB 250331A: MAXI/GSC detection
  88. Fermi GRB 250330A: Global MASTER-Net observations report
  89. IceCube Alert 250330.35: Global MASTER-Net observations report
  90. GRB 250329A: SVOM/VT optical counterpart confirmation
  91. GRB 250327B: LCO optical counterpart detection
  92. EP250321a: LCO optical counterpart detection
  93. EP250321a: Einstein Probe detection of an X-ray transient
  94. EP250226a/GRB 250226A: KAIT optical observations
  95. Fermi trigger No 763933627: Global MASTER-Net observations report
  96. Fermi GRB 250316A: Global MASTER-Net observations report
  97. GRB 250314A: Swift XRT Detection
  98. EP250315a: optical counterpart candidate detected by Gemini North
  99. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  100. Fermi GRB 250313A: Global MASTER-Net observations report

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