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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"

16190 results found.

  1. GRB 250330A: Swift/UVOT Upper Limits
  2. GRB 250330A: Swift-XRT afterglow detection
  3. GRB 250328A: 1.6m Mephisto optical observations
  4. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  5. GRB 250330A: VLT/FORS2 Optical Observations
  6. GRB 250329B: Swift-XRT afterglow detection
  7. GRB 250330A: Swift detection of a burst
  8. GRB 250329B: SVOM/C-GFT optical upper limit
  9. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
  10. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  11. GRB250329A: REM optical afterglow detection
  12. GRB 250329A: Swift-XRT afterglow detection
  13. GRB 250328A: SVOM/VT optical observation
  14. GRB 250329A: Fading optical counterpart detection by LCO.
  15. GRB 250328A: SVOM/C-GFT optical upper limit
  16. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  17. GRB 250329A: SVOM/VT optical counterpart confirmation
  18. GRB 250329A: SVOM detection of a burst
  19. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  20. GRB 250327B: J-band observations with WINTER
  21. GRB 250327B: LCO optical counterpart detection
  22. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  23. GRB 250327B: CrAO and SAO RAS Optical Observations
  24. GRB 250327b: Liverpool Telescope optical observations
  25. GRB 250322A: GRANDMA/TNOT optical upper limits
  26. GRB 250327A: SVOM/VT upper limits on the XRT position
  27. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  28. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  29. GRB 250327B: Las Cumbres optical counterpart detection
  30. GRB 250327B: 1.6m Mephisto optical observations
  31. GRB 250327B: SVOM/VT optically bright counterpart
  32. GRB 250327B: SAO RAS optical candidate
  33. GRB 250327B: SVOM detection of a burst
  34. GRB 250327A: J-band observations with WINTER
  35. GRB 250327A: SVOM/VT optical candidate
  36. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  37. GRB 250327A: DDOTI Optical Observations
  38. GRB 250327A: COLIBRÍ optical upper limit
  39. IPN triangulation of GRB 250322B
  40. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  41. EP250321a: Mondy AZT-33IK Continued Optical Observations
  42. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  43. GRB 250322A: third epoch of NOT optical observations
  44. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  45. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  46. GRB 250322A: further NOT optical observations
  47. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  48. GRB 250322A: Swift/UVOT Upper Limits
  49. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  50. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  51. GRB 250321B: Swift-XRT observations
  52. EP250321a: TNOT Observation of Optical Counterpart
  53. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  54. GRB 250322B: AstroSat CZTI detection of a bright long burst
  55. GRB 250322A: VLT optical observations
  56. GRB 250322A: VLT near-infrared observations
  57. FRB 250316A: DDOTI Continued Optical Observations
  58. GRB 250322A: NOT optical upper limits
  59. GRB 250322A: Enhanced Swift-XRT position
  60. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  61. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  62. EP250321a: Liverpool Telescope optical follow-up
  63. EP250321a: Mondy AZT-33IK Optical Observations
  64. GRB 250322A: Swift detection of a short burst
  65. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  66. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  67. EP250321A: COLIBRÍ Continuing Optical Observations
  68. EP250321a: WFST optical observations
  69. EP250321a: Xinglong 216 decaying optical observations
  70. GRB 250321A: Swift-XRT refined Analysis
  71. EP 250321A: Optical counterpart detection by LCO.
  72. EP250321a: Kinder optical follow-up observations
  73. GRB 250321A: Swift/UVOT Upper Limits
  74. GRB 250320B: SVOM/GRM observation of a long burst
  75. EP250321a: LCO optical counterpart detection
  76. EP250321A: COLIBRÍ Optical Observations
  77. EP250321a: REM optical/NIR afterglow detection
  78. EP250321a: TRT optical counterpart detection
  79. EP250321a: Einstein Probe detection of an X-ray transient
  80. GRB 250321A: GOTO optical upper limits
  81. GRB 250314A: Keck/NIRC2 J-band upper limit
  82. EP250226a/GRB 250226A: KAIT optical observations
  83. GRB 250321A: Swift detection of a burst
  84. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  85. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  86. LIGO/Virgo/KAGRA S250206dm: LIGHETR followup observations of AT2025azn
  87. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  88. GRB 250314A: ATCA radio upper limits
  89. GRB 250317C: SVOM/GRM observation of a long burst
  90. GRB 250317B: Leavitt Observatory optical upper limit
  91. GRB 250309B/AT2025dws: further ATCA observations
  92. GRB 250317B: Mondy AZT-33IK Optical Observations
  93. GRB 250317C: AstroSat CZTI detection
  94. GRB 250317B: NOT optical observations suggest an optical plateau phase
  95. GRB 250317B: OHP/T193 optical observations
  96. GRB250312A: Swift/UVOT Upper Limits
  97. GRB 250317B: REM optical/NIR observations
  98. GRB 250316A: Swift/UVOT Upper Limits
  99. GRB 250314A: REM optical/NIR upper limits
  100. GRB 250316A: AbAO AS-32 Optical Upper Limit

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