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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"

18634 results found.

  1. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  2. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  3. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  4. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  5. GRB 250706B/C: Fermi-LAT detection
  6. GRB 250706B: Swift/UVOT Detection
  7. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  8. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  9. GRB 250702F: GRANDMA observations
  10. GRB 250706A: Swift-XRT refined Analysis
  11. GRB 250706A: Swift/UVOT Upper Limits
  12. GRB 250706A: REM optical/NIR observations
  13. Swift GRB 250706A: Global MASTER-Net observations report
  14. GRB 250706A: JinShan optical upper limits
  15. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  16. GRB250706B: Swift-XRT counterpart detection
  17. GRB 250706A: GROWTH-India Telescope optical upper limit
  18. GRB 250706A: Swift detection of a burst
  19. GRB 250704B: Swift-XRT refined Analysis
  20. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  21. GRB 250704B: Swift/UVOT Upper Limits
  22. GRB 250704A: Swift/UVOT Detection
  23. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  24. GRB 250702F: Kilonova-Catcher optical afterglow detection
  25. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  26. GRB 250704A: SVOM/VT optical observation
  27. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  28. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  29. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  30. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  31. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  32. EP250704a / GRB250704B: Swift-XRT counterpart detection
  33. GRB 250704A: Swift-XRT afterglow detection
  34. GRB 250702B / EP2050702a: FTW optical and NIR observations
  35. Konus-Wind detection of GRB 250702F
  36. GRB 250702F: GROWTH-India Telescope optical observations
  37. EP250702a: WFST optical observations
  38. GRB 250702F: SVOM/VT optical observation
  39. GRB 250702F: Swift/UVOT Detection
  40. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  41. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  42. GRB 250702F: Swift-XRT refined Analysis
  43. GRB 250702F: Fermi GBM Observation
  44. GRB 250702F: Leavitt Observatory optical observations
  45. GRB 250702F: AKO Optical Afterglow Detection
  46. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  47. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  48. GRB 250702F: Skynet Optical Observations
  49. GRB 250424A: VIRT Optical Upper Limit
  50. GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
  51. GRB 250702F: TRT Optical Observation
  52. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  53. GRB 250702F: REM optical afterglow detection
  54. GRB 250702F: DDOTI Optical Observation
  55. GRB 250702B,C,D,E / EP 250702: MAXI/GSC detection
  56. GRB 250702F: COLIBRÍ Observations of the Afterglow
  57. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  58. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  59. GRB 250702F: Enhanced Swift-XRT position
  60. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  61. GRB 250702F: NOT observations of the optical afterglow
  62. GRB 250702F: MASTER optical afterglow observation
  63. GRB 250702F: GOTO optical counterpart detection
  64. GRB 250702F: Ondrejov D50 optical afterglow detection
  65. GRB 250702F: Swift detection of a burst with an optical counterpart
  66. Swift GRB 250702F: Global MASTER-Net observations report
  67. GRB 250628B: Swift-XRT observations
  68. GRB 250628B: SVOM/VT optical upper limit
  69. GRB 250628A: REM optical/NIR upper limits
  70. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  71. GRB 250628A: VLT/X-shooter upper limits
  72. GRB 250628A: Swift/UVOT Upper Limits
  73. GRB 250628A: Swift-XRT refined Analysis
  74. Swift GRB 250628A: Global MASTER-Net observations report
  75. GRB 250628A: Enhanced Swift-XRT position
  76. GRB 250628A: Swift detection of a burst
  77. GRB 250625A: Swift-BAT refined analysis
  78. GRB 250625A: Leavitt Observatory afterglow detection
  79. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  80. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  81. GRB 250625A: SVOM/C-GFT upper limit in early phase
  82. GRB 250625A: GECAM-B detection
  83. GRB 250625A: Swift/UVOT Upper Limits
  84. GRB 250625A: ABObservatory afterglow detection
  85. GRB 250625A: COLIBRÍ optical observations
  86. GRB 250625A: Fermi-LAT detection
  87. GRB 250625A: Swift-XRT refined Analysis
  88. GRB 250625A: JinShan optical observations
  89. GRB250625A: Fermi GBM Observation
  90. Swift GRB 250625A: Global MASTER-Net observations report
  91. GRB 250625A: SVOM/VT optical confirmation
  92. GRB 250620B: Fermi GBM Observation
  93. GRB 250625A: Enhanced Swift-XRT position
  94. GRB 250625A: Swift detection of a burst
  95. GRB 250620A: AstroSat CZTI detection
  96. GRB 241018A: Maidanak optical observations
  97. GRB 250617B: Swift-BAT refined analysis
  98. IPN triangulation of GRB 250620С (long/bright)
  99. GRB 250620A: SVOM/GRM observation of a short burst
  100. GRB250620A: Fermi GBM Observation

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