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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"

18639 results found.

  1. GRB 250713A: SVOM/C-GFT upper limit
  2. GRB 250713A: Swift-XRT observations
  3. GRB 250706A: Swift-BAT refined analysis
  4. GRB 250702F: Swift-BAT refined analysis
  5. GRB 250628A: Swift-BAT refined analysis
  6. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  7. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  8. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  9. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  10. GRB 250706B/C: Fermi-LAT detection
  11. GRB 250706B: Swift/UVOT Detection
  12. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  13. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  14. GRB 250702F: GRANDMA observations
  15. GRB 250706A: Swift-XRT refined Analysis
  16. GRB 250706A: Swift/UVOT Upper Limits
  17. GRB 250706A: REM optical/NIR observations
  18. Swift GRB 250706A: Global MASTER-Net observations report
  19. GRB 250706A: JinShan optical upper limits
  20. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  21. GRB250706B: Swift-XRT counterpart detection
  22. GRB 250706A: GROWTH-India Telescope optical upper limit
  23. GRB 250706A: Swift detection of a burst
  24. GRB 250704B: Swift-XRT refined Analysis
  25. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  26. GRB 250704B: Swift/UVOT Upper Limits
  27. GRB 250704A: Swift/UVOT Detection
  28. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  29. GRB 250702F: Kilonova-Catcher optical afterglow detection
  30. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  31. GRB 250704A: SVOM/VT optical observation
  32. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  33. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  34. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  35. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  36. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  37. EP250704a / GRB250704B: Swift-XRT counterpart detection
  38. GRB 250704A: Swift-XRT afterglow detection
  39. GRB 250702B / EP2050702a: FTW optical and NIR observations
  40. Konus-Wind detection of GRB 250702F
  41. GRB 250702F: GROWTH-India Telescope optical observations
  42. EP250702a: WFST optical observations
  43. GRB 250702F: SVOM/VT optical observation
  44. GRB 250702F: Swift/UVOT Detection
  45. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  46. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  47. GRB 250702F: Swift-XRT refined Analysis
  48. GRB 250702F: Fermi GBM Observation
  49. GRB 250702F: Leavitt Observatory optical observations
  50. GRB 250702F: AKO Optical Afterglow Detection
  51. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  52. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  53. GRB 250702F: Skynet Optical Observations
  54. GRB 250424A: VIRT Optical Upper Limit
  55. GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
  56. GRB 250702F: TRT Optical Observation
  57. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  58. GRB 250702F: REM optical afterglow detection
  59. GRB 250702F: DDOTI Optical Observation
  60. GRB 250702B,C,D,E / EP 250702: MAXI/GSC detection
  61. GRB 250702F: COLIBRÍ Observations of the Afterglow
  62. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  63. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  64. GRB 250702F: Enhanced Swift-XRT position
  65. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  66. GRB 250702F: NOT observations of the optical afterglow
  67. GRB 250702F: MASTER optical afterglow observation
  68. GRB 250702F: GOTO optical counterpart detection
  69. GRB 250702F: Ondrejov D50 optical afterglow detection
  70. GRB 250702F: Swift detection of a burst with an optical counterpart
  71. Swift GRB 250702F: Global MASTER-Net observations report
  72. GRB 250628B: Swift-XRT observations
  73. GRB 250628B: SVOM/VT optical upper limit
  74. GRB 250628A: REM optical/NIR upper limits
  75. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  76. GRB 250628A: VLT/X-shooter upper limits
  77. GRB 250628A: Swift/UVOT Upper Limits
  78. GRB 250628A: Swift-XRT refined Analysis
  79. Swift GRB 250628A: Global MASTER-Net observations report
  80. GRB 250628A: Enhanced Swift-XRT position
  81. GRB 250628A: Swift detection of a burst
  82. GRB 250625A: Swift-BAT refined analysis
  83. GRB 250625A: Leavitt Observatory afterglow detection
  84. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  85. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  86. GRB 250625A: SVOM/C-GFT upper limit in early phase
  87. GRB 250625A: GECAM-B detection
  88. GRB 250625A: Swift/UVOT Upper Limits
  89. GRB 250625A: ABObservatory afterglow detection
  90. GRB 250625A: COLIBRÍ optical observations
  91. GRB 250625A: Fermi-LAT detection
  92. GRB 250625A: Swift-XRT refined Analysis
  93. GRB 250625A: JinShan optical observations
  94. GRB250625A: Fermi GBM Observation
  95. Swift GRB 250625A: Global MASTER-Net observations report
  96. GRB 250625A: SVOM/VT optical confirmation
  97. GRB 250620B: Fermi GBM Observation
  98. GRB 250625A: Enhanced Swift-XRT position
  99. GRB 250625A: Swift detection of a burst
  100. GRB 250620A: AstroSat CZTI detection

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