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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"

26231 results found.

  1. Fermi GRB 250711A: Global MASTER-Net observations report
  2. GRB 250704A: GRANDMA observations
  3. GRB 250711A: BALROG localization (Fermi Trigger 773937617 / GRB 250711611)
  4. GRB 250711A: Fermi GBM Final Real-time Localization
  5. GRB 250704A: SVOM/ECLAIRs refined analysis
  6. GRB 250702B,D,E / EP250702a: ALMA detection
  7. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  8. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  9. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  10. GRB 250709A: Fermi GBM Final Localization
  11. EP/WXT 01709181970: GOTO observations confirm stellar variability
  12. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  13. The EP-WXT trigger 01709181970 is likely a flaring star
  14. Fermi GRB 250708A: Global MASTER-Net observations report
  15. IceCube-250708A: Global MASTER-Net observations report
  16. GRB 250708A: Fermi GBM Final Real-time Localization
  17. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  18. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  19. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  20. GRB 250706B/C: VLT/X-shooter redshift z = 0.942
  21. IceCube-250706A: EP-FXT follow-up observations
  22. GRB 250706B/C: Fermi-LAT detection
  23. IceCube-250706A: Global MASTER-Net observations report
  24. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  25. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  26. GRB 250706B: Swift/UVOT Detection
  27. GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
  28. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  29. GRB 250702F: GRANDMA observations
  30. GRB 250706A: Swift-XRT refined Analysis
  31. GRB 250706B: refined SVOM/MXT data analysis
  32. GRB 250706A: Swift/UVOT Upper Limits
  33. GRB 250706B: REM optical observations
  34. GRB 250706A: REM optical/NIR observations
  35. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  36. IceCube-250416A: DDOTI Optical Upper Limit
  37. IceCube-250706A: COLIBRÍ optical upper limits
  38. Swift GRB 250706A: Global MASTER-Net observations report
  39. GRB 250706A: JinShan optical upper limits
  40. EP250704A: NOWT Detection
  41. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  42. The EP-WXT trigger 01709181580 is likely a flaring star
  43. GRB250706B: Swift-XRT counterpart detection
  44. GRB 250706B: iTelescope optical observations
  45. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  46. GRB 250706B: SVOM/VT optical observation
  47. GRB 250706B: TRT bright optical counterpart detection
  48. GRB 250706A: GROWTH-India Telescope optical upper limit
  49. GRB 250706B: SVOM detection of a long burst
  50. GRB 250706A: Swift detection of a burst
  51. GRB 250704B: Swift-XRT refined Analysis
  52. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  53. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  54. GRB 250704B: Swift/UVOT Upper Limits
  55. GRB 250704A: Swift/UVOT Detection
  56. IPN triangulation of GRB 250703A
  57. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  58. EP250704a/GRB 250704B: FTW optical and NIR observations of the counterpart
  59. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  60. GRB 250702F: Kilonova-Catcher optical afterglow detection
  61. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  62. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  63. EP250704a / GRB 250704B: JinShan optical observations
  64. GRB 250704A: SVOM/VT optical observation
  65. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  66. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  67. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  68. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  69. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  70. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  71. EP250704a / GRB250704B: Swift-XRT counterpart detection
  72. GRB 250704A: Swift-XRT afterglow detection
  73. EP250704a / GRB 250704B - REM observations
  74. GRB 250702F: GROWTH-India Telescope optical observations
  75. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  76. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  77. EP250702a: WFST optical observations
  78. EP250704a: COLIBRÍ optical counterpart candidate
  79. EP250704a: Einstein Probe detection of an X-ray transient
  80. GRB 250704B: SVOM/GRM observation of a short burst
  81. GRB 250702F: optical photometry from Konkoly
  82. GRB 250704A: REM detection of the optical afterglow
  83. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  84. GRB 250702F: SVOM/VT optical observation
  85. GRB 250704A: SVOM detection of a burst
  86. GRB 250702F: Swift/UVOT Detection
  87. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  88. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  89. Fermi GRB 250703A: Global MASTER-Net observations report
  90. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  91. GRB 250702F: Swift-XRT refined Analysis
  92. GRB 250702F: Fermi GBM Observation
  93. GRB 250702F: Leavitt Observatory optical observations
  94. GRB 250702F: AKO Optical Afterglow Detection
  95. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  96. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  97. GRB 250702A: GECAM-B detection
  98. GRB 250702F: Skynet Optical Observations
  99. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  100. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation

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