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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"

19934 results found.

  1. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  2. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  3. GRB 250702F: Swift-XRT refined Analysis
  4. GRB 250702F: Fermi GBM Observation
  5. GRB 250702F: Leavitt Observatory optical observations
  6. GRB 250702F: AKO Optical Afterglow Detection
  7. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  8. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  9. GRB 250702F: Skynet Optical Observations
  10. GRB 250424A: VIRT Optical Upper Limit
  11. GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
  12. GRB 250702F: TRT Optical Observation
  13. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  14. GRB 250702F: REM optical afterglow detection
  15. GRB 250702F: DDOTI Optical Observation
  16. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  17. GRB 250702F: COLIBRÍ Observations of the Afterglow
  18. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  19. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  20. GRB 250702F: Enhanced Swift-XRT position
  21. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  22. GRB 250702F: NOT observations of the optical afterglow
  23. GRB 250702F: MASTER optical afterglow observation
  24. GRB 250702F: GOTO optical counterpart detection
  25. GRB 250702F: Ondrejov D50 optical afterglow detection
  26. GRB 250702F: Swift detection of a burst with an optical counterpart
  27. Swift GRB 250702F: Global MASTER-Net observations report
  28. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  29. GRB 250628B: Swift-XRT observations
  30. GRB 250628B: SVOM/VT optical upper limit
  31. GRB 250628A: REM optical/NIR upper limits
  32. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  33. GRB 250628A: VLT/X-shooter upper limits
  34. GRB 250628A: Swift/UVOT Upper Limits
  35. GRB 250628A: Swift-XRT refined Analysis
  36. Swift GRB 250628A: Global MASTER-Net observations report
  37. GRB 250628A: Enhanced Swift-XRT position
  38. GRB 250628A: Swift detection of a burst
  39. GRB 250625A: Swift-BAT refined analysis
  40. GRB 250625A: Leavitt Observatory afterglow detection
  41. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  42. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  43. GRB 250625A: SVOM/C-GFT upper limit in early phase
  44. GRB 250625A: GECAM-B detection
  45. GRB 250625A: Swift/UVOT Upper Limits
  46. GRB 250625A: ABObservatory afterglow detection
  47. GRB 250625A: COLIBRÍ optical observations
  48. GRB 250625A: Fermi-LAT detection
  49. GRB 250625A: Swift-XRT refined Analysis
  50. GRB 250625A: JinShan optical observations
  51. GRB250625A: Fermi GBM Observation
  52. Swift GRB 250625A: Global MASTER-Net observations report
  53. GRB 250625A: SVOM/VT optical confirmation
  54. GRB 250620B: Fermi GBM Observation
  55. GRB 250625A: Enhanced Swift-XRT position
  56. GRB 250625A: Swift detection of a burst
  57. GRB 250620A: AstroSat CZTI detection
  58. GRB 241018A: Maidanak optical observations
  59. GRB 250617B: Swift-BAT refined analysis
  60. IPN triangulation of GRB 250620C (long/bright)
  61. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  62. GRB 250620A: SVOM/GRM observation of a short burst
  63. GRB250620A: Fermi GBM Observation
  64. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  65. GRB 250619B: Fermi GBM Observation
  66. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  67. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  68. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  69. GRB 250615A: Kilonova-Catcher optical upper limits
  70. GRB 250617B: Assy AZT-20 Optical Observations
  71. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  72. GRB 250615A/EP250615a: FTW optical and NIR observations
  73. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  74. GRB 250617B: Swift/UVOT Detection
  75. GRB 250617B: Kilonova-Catcher optical afterglow detection
  76. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  77. GRB 250617B: NOT NIR observations of the afterglow
  78. GRB 250617B: Swift-XRT refined Analysis
  79. GRB 250617B: SVOM/VT optical observation
  80. Swift GRB 250617B: Global MASTER-Net observations report
  81. GRB 250617B: GOTO optical upper limit
  82. GRB 250617B: Enhanced Swift-XRT position
  83. GRB 250617B: Fermi GBM Observation
  84. GRB 250615A: Swift-BAT refined analysis
  85. GRB 250617B: Fermi GBM Final Localization
  86. GRB 250617B: Ondrejov D50 optical afterglow detection
  87. GRB 250617B: Swift detection of a burst with an optical counterpart
  88. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  89. EP#01709178975: Swift-XRT counterpart detection
  90. Konus-Wind detection of GRB 250615A / EP250615a
  91. GRB 250615A / EP250615a: AstroSat CZTI detection
  92. GRB 250615A: COLIBRÍ optical upper limit
  93. GRB 250615A: DDOTI Optical Upper Limit
  94. GRB 250615A: Swift/UVOT Upper Limits
  95. GRB 250615A: Swift-XRT refined Analysis
  96. GRB 250615A: Enhanced Swift-XRT position
  97. GRB 250615A: Prompt enhanced Swift-XRT position
  98. GRB 250615A: Swift detection of a burst
  99. Swift GRB 250615A: Global MASTER-Net observations report
  100. sb25061207: Mephisto optical upper limits

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