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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"

21451 results found.

  1. GRB 250702F: Kilonova-Catcher optical afterglow detection
  2. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  3. GRB 250704A: SVOM/VT optical observation
  4. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  5. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  6. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  7. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  8. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  9. EP250704a / GRB250704B: Swift-XRT counterpart detection
  10. GRB 250704A: Swift-XRT afterglow detection
  11. GRB 250702B / EP2050702a: FTW optical and NIR observations
  12. Konus-Wind detection of GRB 250702F
  13. GRB 250702F: GROWTH-India Telescope optical observations
  14. EP250702a: WFST optical observations
  15. GRB 250702F: SVOM/VT optical observation
  16. GRB 250702F: Swift/UVOT Detection
  17. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  18. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  19. GRB 250702F: Swift-XRT refined Analysis
  20. GRB 250702F: Fermi GBM Observation
  21. GRB 250702F: Leavitt Observatory optical observations
  22. GRB 250702F: AKO Optical Afterglow Detection
  23. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  24. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  25. GRB 250702F: Skynet Optical Observations
  26. GRB 250424A: VIRT Optical Upper Limit
  27. GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
  28. GRB 250702F: TRT Optical Observation
  29. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  30. GRB 250702F: REM optical afterglow detection
  31. GRB 250702F: DDOTI Optical Observation
  32. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  33. GRB 250702F: COLIBRÍ Observations of the Afterglow
  34. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  35. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  36. GRB 250702F: Enhanced Swift-XRT position
  37. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  38. GRB 250702F: NOT observations of the optical afterglow
  39. GRB 250702F: MASTER optical afterglow observation
  40. GRB 250702F: GOTO optical counterpart detection
  41. GRB 250702F: Ondrejov D50 optical afterglow detection
  42. GRB 250702F: Swift detection of a burst with an optical counterpart
  43. Swift GRB 250702F: Global MASTER-Net observations report
  44. GRB 250628B: Swift-XRT observations
  45. GRB 250628B: SVOM/VT optical upper limit
  46. GRB 250628A: REM optical/NIR upper limits
  47. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  48. GRB 250628A: VLT/X-shooter upper limits
  49. GRB 250628A: Swift/UVOT Upper Limits
  50. GRB 250628A: Swift-XRT refined Analysis
  51. Swift GRB 250628A: Global MASTER-Net observations report
  52. GRB 250628A: Enhanced Swift-XRT position
  53. GRB 250628A: Swift detection of a burst
  54. GRB 250625A: Swift-BAT refined analysis
  55. GRB 250625A: Leavitt Observatory afterglow detection
  56. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  57. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  58. GRB 250625A: SVOM/C-GFT upper limit in early phase
  59. GRB 250625A: GECAM-B detection
  60. GRB 250625A: Swift/UVOT Upper Limits
  61. GRB 250625A: ABObservatory afterglow detection
  62. GRB 250625A: COLIBRÍ optical observations
  63. GRB 250625A: Fermi-LAT detection
  64. GRB 250625A: Swift-XRT refined Analysis
  65. GRB 250625A: JinShan optical observations
  66. GRB250625A: Fermi GBM Observation
  67. Swift GRB 250625A: Global MASTER-Net observations report
  68. GRB 250625A: SVOM/VT optical confirmation
  69. GRB 250620B: Fermi GBM Observation
  70. GRB 250625A: SAO RAS possible optical afterglow
  71. GRB 250625A: Enhanced Swift-XRT position
  72. GRB 250625A: Swift detection of a burst
  73. GRB 250620A: AstroSat CZTI detection
  74. GRB 241018A: Maidanak optical observations
  75. GRB 250617B: Swift-BAT refined analysis
  76. IPN triangulation of GRB 250620C (long/bright)
  77. GRB 250620A: SVOM/GRM observation of a short burst
  78. GRB250620A: Fermi GBM Observation
  79. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  80. GRB 250619B: Fermi GBM Observation
  81. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  82. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  83. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  84. GRB 250615A: Kilonova-Catcher optical upper limits
  85. GRB 250617B: Assy AZT-20 Optical Observations
  86. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  87. GRB 250615A/EP250615a: FTW optical and NIR observations
  88. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  89. GRB 250617B: Swift/UVOT Detection
  90. GRB 250617B: Kilonova-Catcher optical afterglow detection
  91. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  92. GRB 250617B: NOT NIR observations of the afterglow
  93. GRB 250617B: Swift-XRT refined Analysis
  94. GRB 250617B: SVOM/VT optical observation
  95. Swift GRB 250617B: Global MASTER-Net observations report
  96. GRB 250617B: GOTO optical upper limit
  97. GRB 250617B: Enhanced Swift-XRT position
  98. GRB 250617B: Fermi GBM Observation
  99. GRB 250615A: Swift-BAT refined analysis
  100. GRB 250617B: Fermi GBM Final Localization

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