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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"

19333 results found.

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

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