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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"

24310 results found.

  1. GRB 250713A: NOT optical upper limits
  2. GRB 250713A: OHP/T193 upper limit
  3. GRB 250713A: SVOM/C-GFT upper limit
  4. GRB 250714A: Fermi GBM Final Real-time Localization
  5. GRB 250713A: Swift-XRT observations
  6. GRB 250713A: EP-FXT counterpart detection
  7. EP250711a: COLIBRÍ continuous optical observations
  8. GRB 250706A: Swift-BAT refined analysis
  9. GRB 250702F: Swift-BAT refined analysis
  10. GRB 250628A: Swift-BAT refined analysis
  11. GRB 250713A: JinShan optical upper limits
  12. GRB 250713A: SVOM detection of a short burst
  13. EP250711a: Global MASTER-Net observations report
  14. GRB 250711A: DDOTI Optical Upper Limit
  15. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  16. GRB 250711A: SVOM/GRM observation
  17. EP250711a: NOT optical counterpart candidate
  18. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  19. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  20. Fermi GRB 250711A: Global MASTER-Net observations report
  21. GRB 250711A: BALROG localization (Fermi Trigger 773937617 / GRB 250711611)
  22. GRB 250711A: Fermi GBM Final Real-time Localization
  23. GRB 250702B,D,E / EP250702a: ALMA detection
  24. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  25. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  26. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  27. GRB 250709A: Fermi GBM Final Localization
  28. EP/WXT 01709181970: GOTO observations confirm stellar variability
  29. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  30. The EP-WXT trigger 01709181970 is likely a flaring star
  31. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  32. Fermi GRB 250708A: Global MASTER-Net observations report
  33. IceCube-250708A: Global MASTER-Net observations report
  34. GRB 250708A: Fermi GBM Final Real-time Localization
  35. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  36. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  37. GRB 250706B/C: VLT/X-shooter redshift z = 0.942
  38. IceCube-250706A: EP-FXT follow-up observations
  39. GRB 250706B/C: Fermi-LAT detection
  40. IceCube-250706A: Global MASTER-Net observations report
  41. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  42. GRB 250706B: Swift/UVOT Detection
  43. GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
  44. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  45. GRB 250706A: Swift-XRT refined Analysis
  46. GRB 250706B: refined SVOM/MXT data analysis
  47. GRB 250706A: Swift/UVOT Upper Limits
  48. GRB 250706B: REM optical observations
  49. GRB 250706A: REM optical/NIR observations
  50. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  51. IceCube-250416A: DDOTI Optical Upper Limit
  52. IceCube-250706A: COLIBRÍ optical upper limits
  53. Swift GRB 250706A: Global MASTER-Net observations report
  54. GRB 250706A: JinShan optical upper limits
  55. EP250704A: NOWT Detection
  56. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  57. The EP-WXT trigger 01709181580 is likely a flaring star
  58. GRB250706B: Swift-XRT counterpart detection
  59. GRB 250706B: iTelescope optical observations
  60. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  61. GRB 250706B: SVOM/VT optical observation
  62. GRB 250706B: TRT bright optical counterpart detection
  63. GRB 250706A: GROWTH-India Telescope optical upper limit
  64. GRB 250706B: SVOM detection of a long burst
  65. GRB 250706A: Swift detection of a burst
  66. GRB 250704B: Swift-XRT refined Analysis
  67. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  68. GRB 250704B: Swift/UVOT Upper Limits
  69. GRB 250704A: Swift/UVOT Detection
  70. IPN triangulation of GRB 250703A
  71. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  72. EP250704a/GRB 250704B: FTW optical and NIR observations of the counterpart
  73. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  74. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  75. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  76. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  77. EP250704a / GRB 250704B: JinShan optical observations
  78. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  79. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  80. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  81. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  82. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  83. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  84. EP250704a / GRB250704B: Swift-XRT counterpart detection
  85. GRB 250704A: Swift-XRT afterglow detection
  86. EP250704a / GRB 250704B - REM observations
  87. GRB 250702F: GROWTH-India Telescope optical observations
  88. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  89. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  90. EP250702a: WFST optical observations
  91. EP250704a: COLIBRÍ optical counterpart candidate
  92. GRB 250704B: SVOM/GRM observation of a short burst
  93. GRB 250702F: optical photometry from Konkoly
  94. GRB 250704A: REM detection of the optical afterglow
  95. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  96. GRB 250702F: SVOM/VT optical observation
  97. GRB 250704A: SVOM detection of a burst
  98. GRB 250702F: Swift/UVOT Detection
  99. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  100. Fermi GRB 250703A: Global MASTER-Net observations report

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