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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.

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subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

20356 results found.

  1. GRB 250706B: REM optical observations
  2. GRB 250706A: REM optical/NIR observations
  3. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  4. IceCube-250416A: DDOTI Optical Upper Limit
  5. IceCube-250706A: COLIBRÍ optical upper limits
  6. GRB 250706A: JinShan optical upper limits
  7. GRB 250706A: SAO RAS optical observations
  8. EP250704A: NOWT Detection
  9. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  10. GRB 250706B: iTelescope optical observations
  11. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  12. GRB 250706B: SVOM/VT optical observation
  13. GRB 250706B: TRT bright optical counterpart detection
  14. GRB 250706A: GROWTH-India Telescope optical upper limit
  15. GRB 250706B: SVOM detection of a long burst
  16. GRB 250706A: Swift detection of a burst
  17. GRB 250704B: Swift-XRT refined Analysis
  18. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  19. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  20. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  21. GRB 250704B: Swift/UVOT Upper Limits
  22. GRB 250704A: Swift/UVOT Detection
  23. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  24. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  25. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  26. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  27. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  28. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  29. GRB 250702F: Kilonova-Catcher optical afterglow detection
  30. GRB 250702F: Monte Agliale Observatory optical observations
  31. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  32. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  33. EP250704a / GRB 250704B: JinShan optical observations
  34. EP250704a / GRB 250704B: SAO RAS optical observations
  35. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  36. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  37. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  38. EP 250704a: BOOTES-5 optical detection
  39. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  40. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  41. GRB 250704A: Swift-XRT afterglow detection
  42. EP250704a / GRB 250704B - REM observations
  43. GRB 250702F: GROWTH-India Telescope optical observations
  44. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  45. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  46. EP250702a: WFST optical observations
  47. EP250704a: COLIBRÍ optical counterpart candidate
  48. EP250704a: Einstein Probe detection of an X-ray transient
  49. GRB 250704A: REM detection of the optical afterglow
  50. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  51. GRB 250704A: SVOM detection of a burst
  52. GRB 250702F: Swift/UVOT Detection
  53. GRB 250702F: Leavitt Observatory optical observations
  54. GRB 250702F: AKO Optical Afterglow Detection
  55. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  56. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  57. GRB 250702F: Skynet Optical Observations
  58. GRB 250424A: VIRT Optical Upper Limit
  59. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  60. GRB 250702F: TRT Optical Observation
  61. GRB 250703A: DDOTI Optical Upper Limit
  62. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  63. GRB 250702F: REM optical afterglow detection
  64. GRB 250702F: DDOTI Optical Observation
  65. GRB 250702F: COLIBRÍ Observations of the Afterglow
  66. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  67. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  68. GRB 250702F: Enhanced Swift-XRT position
  69. GRB 250702F: NOT observations of the optical afterglow
  70. GRB 250702F: Ondrejov D50 optical afterglow detection
  71. GRB 250702F: Swift detection of a burst with an optical counterpart
  72. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  73. LIGO/Virgo/KAGRA S250701bq: Identification of a GW compact binary merger candidate
  74. GRB 250628B: EP-FXT counterpart detection
  75. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  76. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  77. GRB 250628A: REM optical/NIR upper limits
  78. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  79. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  80. GRB 250628A: VLT/X-shooter upper limits
  81. GRB 250628A: Swift/UVOT Upper Limits
  82. GRB 250628A: Enhanced Swift-XRT position
  83. GRB 250628A: Swift detection of a burst
  84. GRB 250625A: Leavitt Observatory afterglow detection
  85. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  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: OHP/T193 optical detection
  91. GRB 250625A: COLIBRÍ optical observations
  92. GRB 250625A: Swift-XRT refined Analysis
  93. GRB 250625A: JinShan optical observations
  94. GRB 250625A: SAO RAS possible optical afterglow
  95. GRB 250625A: Enhanced Swift-XRT position
  96. GRB 250625A: Swift detection of a burst
  97. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  98. GRB 241018A: Maidanak optical observations
  99. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
  100. IPN triangulation of GRB 250620C (long/bright)

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