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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"

27499 results found.

  1. GRB 250716A: Swift-XRT afterglow detection
  2. GRB 250717B: Fermi GBM Final Real-time Localization
  3. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  4. GRB 250717A: Fermi GBM Final Real-time Localization
  5. GRB 250716A: Swift ToO observations
  6. GRB 250716A: Fermi GBM Final Real-time Localization
  7. GRB 250715A: Fermi GBM Final Real-time Localization
  8. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  9. GRB 250713A: SVOM/VT optical upper limit
  10. GRB 250713A: SVOM/C-GFT upper limit
  11. GRB 250714A: Fermi GBM Final Real-time Localization
  12. GRB 250706B/C: 7DT Follow-up Observations
  13. GRB 250713A: Swift-XRT observations
  14. GRB 250713A: EP-FXT counterpart detection
  15. GRB 250713A: SVOM detection of a long burst
  16. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  17. GRB 250711A: Fermi GBM Final Real-time Localization
  18. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  19. GRB 250704B / EP250704a: 1.3 GHz MeerKAT Detection
  20. GRB 250702B,D,E / EP250702a: ALMA detection
  21. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  22. GRB 250709A: Fermi GBM Final Localization
  23. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  24. GRB 250706B/C: Insight-HXMT detection
  25. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  26. EP250704a/GRB 250704B: 10 GHz VLA detection
  27. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  28. IPN triangulation of GRB 250706C (consistent with the GRB 250706B)
  29. IceCube-250708A - IceCube observation of a high-energy neutrino candidate track-like event
  30. GRB 250704B / EP250704a: VLA radio detection
  31. GRB 250708A: Fermi GBM Final Real-time Localization
  32. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  33. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  34. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  35. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  36. GRB 250702F: radio detection with the VLA
  37. GRB 250706B/C: VLT/X-shooter redshift z = 0.942
  38. GRB 250706B/C: Fermi-LAT detection
  39. GRB 250706B: Swift/UVOT Detection
  40. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  41. GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
  42. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  43. GRB 250702F: GRANDMA observations
  44. GRB 250706A: Swift-XRT refined Analysis
  45. GRB 250706B: refined SVOM/MXT data analysis
  46. GRB 250706A: Swift/UVOT Upper Limits
  47. GRB 250706B: REM optical observations
  48. GRB 250706A: REM optical/NIR observations
  49. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  50. IceCube-250416A: DDOTI Optical Upper Limit
  51. GRB 250706A: JinShan optical upper limits
  52. GRB 250706A: SAO RAS optical observations
  53. EP250704A: NOWT Detection
  54. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  55. GRB250706B: Swift-XRT counterpart detection
  56. GRB 250706B: iTelescope optical observations
  57. IceCube-250706A - IceCube observation of a high-energy neutrino candidate track-like event
  58. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  59. GRB 250706B: SVOM/VT optical observation
  60. GRB 250706B: TRT bright optical counterpart detection
  61. GRB 250706A: GROWTH-India Telescope optical upper limit
  62. GRB 250706B: SVOM detection of a long burst
  63. GRB 250706A: Swift detection of a burst
  64. GRB 250704B: Swift-XRT refined Analysis
  65. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  66. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  67. GRB 250703A: EIRSAT-1 GMOD Detection
  68. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  69. GRB 250704B: Swift/UVOT Upper Limits
  70. GRB 250704A: Swift/UVOT Detection
  71. GRB 250704B: Insight-HXMT detection
  72. Konus-Wind detection of GRB 250703A
  73. IPN triangulation of GRB 250703A
  74. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  75. Konus-Wind detection of short/hard GRB 250704B/ EP250704a
  76. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  77. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  78. GRB 250702F: Kilonova-Catcher optical afterglow detection
  79. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  80. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  81. EP250704a / GRB 250704B: JinShan optical observations
  82. GRB 250704A: SVOM/VT optical observation
  83. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  84. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  85. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  86. EP 250704a: BOOTES-5 optical detection
  87. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  88. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  89. GRB 250702A: Insight-HXMT detection
  90. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  91. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  92. EP250704a / GRB250704B: Swift-XRT counterpart detection
  93. GRB 250704A: Swift-XRT afterglow detection
  94. GRB 250702B / EP2050702a: FTW optical and NIR observations
  95. Konus-Wind detection of GRB 250702F
  96. EP250704a / GRB 250704B - REM observations
  97. GRB 250702F: GROWTH-India Telescope optical observations
  98. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  99. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  100. EP250702a: WFST optical observations

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