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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"

18640 results found.

  1. GRB 250716A: Swift ToO observations
  2. GRB 250713A: SVOM/C-GFT upper limit
  3. GRB 250713A: Swift-XRT observations
  4. GRB 250706A: Swift-BAT refined analysis
  5. GRB 250702F: Swift-BAT refined analysis
  6. GRB 250628A: Swift-BAT refined analysis
  7. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  8. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  9. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  10. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  11. GRB 250706B/C: Fermi-LAT detection
  12. GRB 250706B: Swift/UVOT Detection
  13. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  14. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  15. GRB 250702F: GRANDMA observations
  16. GRB 250706A: Swift-XRT refined Analysis
  17. GRB 250706A: Swift/UVOT Upper Limits
  18. GRB 250706A: REM optical/NIR observations
  19. Swift GRB 250706A: Global MASTER-Net observations report
  20. GRB 250706A: JinShan optical upper limits
  21. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  22. GRB250706B: Swift-XRT counterpart detection
  23. GRB 250706A: GROWTH-India Telescope optical upper limit
  24. GRB 250706A: Swift detection of a burst
  25. GRB 250704B: Swift-XRT refined Analysis
  26. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  27. GRB 250704B: Swift/UVOT Upper Limits
  28. GRB 250704A: Swift/UVOT Detection
  29. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  30. GRB 250702F: Kilonova-Catcher optical afterglow detection
  31. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  32. GRB 250704A: SVOM/VT optical observation
  33. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  34. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  35. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  36. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  37. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  38. EP250704a / GRB250704B: Swift-XRT counterpart detection
  39. GRB 250704A: Swift-XRT afterglow detection
  40. GRB 250702B / EP2050702a: FTW optical and NIR observations
  41. Konus-Wind detection of GRB 250702F
  42. GRB 250702F: GROWTH-India Telescope optical observations
  43. EP250702a: WFST optical observations
  44. GRB 250702F: SVOM/VT optical observation
  45. GRB 250702F: Swift/UVOT Detection
  46. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  47. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  48. GRB 250702F: Swift-XRT refined Analysis
  49. GRB 250702F: Fermi GBM Observation
  50. GRB 250702F: Leavitt Observatory optical observations
  51. GRB 250702F: AKO Optical Afterglow Detection
  52. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  53. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  54. GRB 250702F: Skynet Optical Observations
  55. GRB 250424A: VIRT Optical Upper Limit
  56. GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
  57. GRB 250702F: TRT Optical Observation
  58. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  59. GRB 250702F: REM optical afterglow detection
  60. GRB 250702F: DDOTI Optical Observation
  61. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  62. GRB 250702F: COLIBRÍ Observations of the Afterglow
  63. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  64. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  65. GRB 250702F: Enhanced Swift-XRT position
  66. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  67. GRB 250702F: NOT observations of the optical afterglow
  68. GRB 250702F: MASTER optical afterglow observation
  69. GRB 250702F: GOTO optical counterpart detection
  70. GRB 250702F: Ondrejov D50 optical afterglow detection
  71. GRB 250702F: Swift detection of a burst with an optical counterpart
  72. Swift GRB 250702F: Global MASTER-Net observations report
  73. GRB 250628B: Swift-XRT observations
  74. GRB 250628B: SVOM/VT optical upper limit
  75. GRB 250628A: REM optical/NIR upper limits
  76. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  77. GRB 250628A: VLT/X-shooter upper limits
  78. GRB 250628A: Swift/UVOT Upper Limits
  79. GRB 250628A: Swift-XRT refined Analysis
  80. Swift GRB 250628A: Global MASTER-Net observations report
  81. GRB 250628A: Enhanced Swift-XRT position
  82. GRB 250628A: Swift detection of a burst
  83. GRB 250625A: Swift-BAT refined analysis
  84. GRB 250625A: Leavitt Observatory afterglow detection
  85. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  86. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  87. GRB 250625A: SVOM/C-GFT upper limit in early phase
  88. GRB 250625A: GECAM-B detection
  89. GRB 250625A: Swift/UVOT Upper Limits
  90. GRB 250625A: ABObservatory afterglow detection
  91. GRB 250625A: COLIBRÍ optical observations
  92. GRB 250625A: Fermi-LAT detection
  93. GRB 250625A: Swift-XRT refined Analysis
  94. GRB 250625A: JinShan optical observations
  95. GRB250625A: Fermi GBM Observation
  96. Swift GRB 250625A: Global MASTER-Net observations report
  97. GRB 250625A: SVOM/VT optical confirmation
  98. GRB 250620B: Fermi GBM Observation
  99. GRB 250625A: Enhanced Swift-XRT position
  100. GRB 250625A: Swift detection of a burst

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