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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"

27549 results found.

  1. GRB 250725A: PRIME near-infrared observations
  2. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  3. GRB: Clarification on Gamma-Ray Burst Naming Convention
  4. GRB 250728A: Swift-XRT observations
  5. EP-WXT trigger 01709195487: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  6. GRB 250728A: COLIBRÍ optical upper limit
  7. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT detection of a new source, AT 2025smm
  8. GRB 250728A: Swift ToO observations
  9. GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
  10. GRB 250727A: AST3-2 Upper limit
  11. GRB 250727A: EP-FXT counterpart detection
  12. GRB250727A: SVOM/VT optical upper limit
  13. GRB 250727A: Swift-XRT observations
  14. GRB 250727A: SVOM detection of a burst
  15. Swift detection of the Soft Gamma Repeater PSR J1647-4552
  16. GRB 250725A: Swift-XRT refined Analysis
  17. GRB 250725A: Fermi GBM Observation
  18. Konus-Wind detection of GRB 250725A
  19. GRB 250725A: Swift/UVOT Upper Limits
  20. GRB 250725A: Fermi-LAT detection
  21. GRB 250725A: VLT/FORS2 spectroscopic redshift z = 5.26
  22. GRB 250725A: BOOTES-7 early optical detection
  23. GRB 250725A: SVOM/VT optical candidate
  24. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  25. GRB 250725A: Enhanced Swift-XRT position
  26. GRB 250725A: Swift detection of a burst
  27. Swift GRB 250725A: Global MASTER-Net OT detection
  28. GRB 250725A: Fermi GBM Final Real-time Localization
  29. EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
  30. EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz
  31. SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
  32. GRB 250723B: Fermi GBM Final Real-time Localization
  33. GRB 250723A: Fermi GBM Final Real-time Localization
  34. SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
  35. GRB 250721A: Swift-XRT observations
  36. GRB 250722A: Fermi GBM Final Real-time Localization
  37. GRB 250721A: Tiled Swift observations
  38. GRB 250721A: MAXI/GSC detection
  39. GRB 250721A: Fermi GBM Final Localization
  40. GRB 250720B: Fermi GBM Final Localization Correction
  41. GRB 250720A: Fermi GBM Final Localization
  42. GRB 250717B: COLIBRÍ optical upper limit
  43. GRB 250717B: Swift-XRT observations
  44. GRB 250718B: Fermi GBM Final Localization Correction
  45. GRB 250718B: Fermi GBM Final Real-time Localization
  46. Swift Trigger 1334535: a possible GRB 250718A
  47. GRB 250717B: Swift ToO observations
  48. GRB 270713A: Kitab and AbAO Optical Observations
  49. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  50. Konus-Wind detection of GRB 250716A
  51. GRB 250716A: Swift-XRT afterglow detection
  52. GRB 250717B: Fermi GBM Final Real-time Localization
  53. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  54. GRB 250717A: Fermi GBM Final Real-time Localization
  55. GRB 250716A: Swift ToO observations
  56. GRB 250716A: Fermi GBM Final Real-time Localization
  57. GRB 250715A: Fermi GBM Final Real-time Localization
  58. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  59. GRB 250713A: SVOM/VT optical upper limit
  60. GRB 250713A: SVOM/C-GFT upper limit
  61. GRB 250714A: Fermi GBM Final Real-time Localization
  62. GRB 250706B/C: 7DT Follow-up Observations
  63. GRB 250713A: Swift-XRT observations
  64. GRB 250713A: EP-FXT counterpart detection
  65. GRB 250713A: SVOM detection of a long burst
  66. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  67. GRB 250711A: Fermi GBM Final Real-time Localization
  68. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  69. GRB 250704B / EP250704a: 1.3 GHz MeerKAT Detection
  70. GRB 250702B,D,E / EP250702a: ALMA detection
  71. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  72. GRB 250709A: Fermi GBM Final Localization
  73. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  74. GRB 250706B/C: Insight-HXMT detection
  75. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  76. EP250704a/GRB 250704B: 10 GHz VLA detection
  77. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  78. IPN triangulation of GRB 250706C (consistent with the GRB 250706B)
  79. IceCube-250708A - IceCube observation of a high-energy neutrino candidate track-like event
  80. GRB 250704B / EP250704a: VLA radio detection
  81. GRB 250708A: Fermi GBM Final Real-time Localization
  82. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  83. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  84. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  85. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  86. GRB 250702F: radio detection with the VLA
  87. GRB 250706B/C: VLT/X-shooter redshift z = 0.942
  88. GRB 250706B/C: Fermi-LAT detection
  89. GRB 250706B: Swift/UVOT Detection
  90. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  91. GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
  92. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  93. GRB 250702F: GRANDMA observations
  94. GRB 250706A: Swift-XRT refined Analysis
  95. GRB 250706B: refined SVOM/MXT data analysis
  96. GRB 250706A: Swift/UVOT Upper Limits
  97. GRB 250706B: REM optical observations
  98. GRB 250706A: REM optical/NIR observations
  99. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  100. IceCube-250416A: DDOTI Optical Upper Limit

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