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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').
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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"

17213 results found.

  1. GRB 250403A: KAIT optical observations
  2. EP250404a: AKO Optical Afterglow Detection
  3. EP250404a: LAST detection of optical counterpart
  4. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  5. GRB 250327B: VIRT Optical Upper Limit
  6. EP250404a: Mephisto multi-band optical detection
  7. EP250321A: J band upper limit by SYSU 80cm telescope
  8. EP250404a: Nanshan/HMT optical counterpart detection
  9. EP250404a: Einstein Probe detection of an X-ray transient
  10. GRB 250403A: Swift/UVOT Detection
  11. GRB 250402A: Swift/UVOT Upper Limits
  12. EP250402a: Optical upper limit with Kinder observations
  13. GRB 250403A: REM NIR afterglow detection
  14. GRB 250403A: LCO optical counterpart detection
  15. GRB 250403A: JinShan optical observations
  16. GRB 250403A: Optical counterpart detection by LCO.
  17. GRB 250403A: GMG Optical Observation
  18. GRB 250403A: 1.6m Mephisto multi-band optical detection
  19. GRB 250403A: SVOM/C-GFT optical observations
  20. GRB 250403A : SVOM detection of a burst
  21. GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  22. GRB 250402A: REM optical/NIR upper limits
  23. GRB 250402A: LCO optical counterpart detection
  24. EP250402a: Einstein Probe detection of a fast X-ray transient
  25. GRB 250402B: AstroSat CZTI detection of a short burst
  26. GRB 250402A: SVOM/VT optical counterpart
  27. GRB 250402A: SVOM detection of a burst
  28. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  29. GRB 250329B: Swift/UVOT Upper Limit
  30. GRB 250329A: Swift/UVOT Upper Limit
  31. GRB 250327B: Swift/UVOT Detection
  32. GRB 250327A: Swift/UVOT Upper Limits
  33. GRB 250331E: SVOM/GRM observation
  34. GRB 250327B: Kilonova-Catcher Observations
  35. GRB 250331C: Swift/UVOT Upper Limits
  36. GRB 250331B: Swift/UVOT Upper Limits
  37. GRB 250328A: AbAO AS-32 Optical Observations
  38. GRB 250219A: NOT candidate host galaxy detection
  39. GRB 250330B: SVOM/GRM observation of a short burst
  40. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  41. GRB 250331D: Swift ToO observations
  42. GRB 250331C: Enhanced Swift-XRT position
  43. GRB 250331B: Enhanced Swift-XRT position
  44. GRB 250330A: VLT/FORS2 Afterglow Detection
  45. GRB20250327B: 45th Parallel Observatory upper limit
  46. GRB 250328A: Swift/UVOT Detection
  47. GRB 250328A: Swift-XRT refined Analysis
  48. GRB 250330A: Fermi GBM Observation
  49. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  50. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  51. GRB 250331C: Swift detection of a burst
  52. GRB 250331B: Swift detection of a burst
  53. SVOM/sb25033102: SVOM detection of an X-ray transient
  54. LIGO/Virgo/KAGRA S250331o: Identification of a GW compact binary merger candidate
  55. GRB 250330A: Swift/UVOT Upper Limits
  56. GRB 250330A: Swift-XRT afterglow detection
  57. GRB 250328A: 1.6m Mephisto optical observations
  58. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  59. GRB 250330A: VLT/FORS2 Optical Observations
  60. GRB 250329B: Swift-XRT afterglow detection
  61. GRB 250330A: Swift detection of a burst
  62. GRB 250329B: SVOM/C-GFT optical upper limit
  63. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  64. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
  65. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  66. GRB250329A: REM optical afterglow detection
  67. GRB 250329B: SVOM detection of a faint transient
  68. GRB 250329A: Swift-XRT afterglow detection
  69. GRB 250328A: SVOM/VT optical observation
  70. GRB 250329A: Fading optical counterpart detection by LCO.
  71. GRB 250328A: SVOM/C-GFT optical upper limit
  72. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  73. GRB 250329A: SVOM/VT optical counterpart confirmation
  74. GRB 250329A: SVOM detection of a burst
  75. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  76. GRB 250327B: J-band observations with WINTER
  77. GRB 250327B: LCO optical counterpart detection
  78. GRB 250328A: SVOM detection of a burst
  79. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  80. GRB 250327B: CrAO and SAO RAS Optical Observations
  81. GRB 250327b: Liverpool Telescope optical observations
  82. GRB 250322A: GRANDMA/TNOT optical upper limits
  83. GRB 250327A: SVOM/VT upper limits on the XRT position
  84. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  85. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  86. GRB 250327B: Las Cumbres optical counterpart detection
  87. GRB 250327B: 1.6m Mephisto optical observations
  88. GRB 250327B: SVOM/VT optically bright counterpart
  89. GRB 250327B: SAO RAS optical candidate
  90. GRB 250327B: SVOM detection of a burst
  91. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  92. GRB 250327A: J-band observations with WINTER
  93. GRB 250327A: SVOM/VT optical candidate
  94. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  95. GRB 250327A: DDOTI Optical Observations
  96. GRB 250327A: COLIBRÍ optical upper limit
  97. IPN triangulation of GRB 250322B
  98. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  99. EP250321a: Mondy AZT-33IK Continued Optical Observations
  100. Swift follow-up observations of FRB250316A and EP J120944.2+585060

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