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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"

18023 results found.

  1. GRB 250225B: REM NIR upper limits
  2. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  3. EP250223a: CrAO ZTSH optical observation
  4. GRB 250225B: VLT optical and near-infrared candidate counterpart
  5. GRB 250225B: SVOM/GRM observation of a long burst
  6. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  7. EP250226a / GRB 250226A: TRT optical counterpart observation
  8. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  9. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  10. EP250223a: GMG Optical Observation
  11. EP250225a: Einstein Probe detected of a fast X-ray transient
  12. EP250223a: GROWTH-India Telescope optical observations
  13. EP250215A: J band upper limit by SYSU 80cm telescope
  14. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  15. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  16. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  17. EP250223a: Kinder optical follow-up observations
  18. GRB 250222A: SVOM/GRM observation of a burst
  19. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  20. EP250223a: REM NIR upper limit
  21. EP250223a: TRT optical afterglow observation
  22. EP250223a: refined analysis of the EP-WXT and FXT observations
  23. EP250223a: 1.6m Mephisto and 50cm array observations
  24. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  25. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO trigger with ID 762004910: Identification of a GW compact binary merger candidate possibly associated with a sub-threshold Swift/BAT-GUANO trigger
  26. EP250223a: OASDG optical observations
  27. EP250223a: early optical detection by BOOTES-4
  28. EP250223a: NOT redshift z = 2.756
  29. EP250223a: NOT optical afterglow candidate
  30. GRB 250221A: VLA radio detection
  31. EP250223a: Einstein Probe detection of an X-ray transient
  32. GRB 250221A: Optical counterpart detection by LCO.
  33. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  34. GRB 250221A: GRANDMA/TAROT Detection
  35. GRB 250221A: 1.6m Mephisto optical detection
  36. GRB 250221A: AKO Optical Upper Limit
  37. GRB 250221A: Swift/UVOT Detection
  38. EP250220a: Liverpool Telescope upper limits
  39. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  40. GRB 250221A: REM optical/NIR afterglow detection
  41. GRB 250221A: Enhanced Swift-XRT position
  42. EP250220a: 1.6m Mephisto observations
  43. EP250220a: Liverpool Telescope optical upper limits
  44. EP250220a: Optical upper limit with Kinder observations
  45. SVOM trigger sb25022102 is not an astrophysical event
  46. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  47. GRB 250221A: Swift detection of a burst with an optical counterpart
  48. EP250220a: Xinglong optical upper limit
  49. EP250220a: EP-WXT detection of a fast X-ray transient
  50. Konus-Wind detection of GRB 250217C (short)
  51. GRB 250219A: Swift/UVOT Upper Limits
  52. GRB 250219A: OHP/T193 optical upper limit
  53. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  54. GRB 250219A: 1.6m Mephisto optical upper limits
  55. Konus-Wind detection of GRB 250215A / EP250215a
  56. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  57. GRB 250217C: Swift-XRT observations
  58. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  59. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  60. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  61. GRB 250217C: SVOM/GRM observation
  62. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  63. SVOM/sb25021804: SVOM detection of a long X-ray transient
  64. GRB 250213A: Swift-XRT observations
  65. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  66. GRANDMA/OPD observations of GRB250215A
  67. GRB 250215A / EP250215a: LCO detection of the afterglow
  68. GRB 250215A: Swift/UVOT Upper Limits
  69. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  70. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  71. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  72. GRB 250215A: SVOM/GRM observation
  73. EP250215a / GRB 250215A: AstroSat CZTI detection
  74. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  75. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  76. EP250207b: Xinglong optical upper limit
  77. Fermi GRB 250214A: Global MASTER-Net observations report
  78. EP250212a: Xinglong optical upper limit
  79. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  80. GRB 250205A: VIRT Optical Upper Limit
  81. GRB 250205A: Leavitt Observatory optical upper limit
  82. EP250207B: Chandra localization of the X-ray counterpart
  83. EP250207b: VLA radio upper limits
  84. EP250212a: Liverpool Telescope optical upper limits
  85. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  86. GRB250101A: Radio upper limits from GMRT observations
  87. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  88. EP250207B: GTC z-band Observations
  89. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  90. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  91. EP250207b: NOT optical counterpart candidate
  92. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  93. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  94. GRB 250205A / EP250205A: radio detection with the VLA
  95. EP250207b: Tentative z-band brightening source
  96. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  97. Konus-Wind detection of GRB 250206A
  98. GRB 250210A: SVOM/GRM observation of a long burst
  99. EP250207b: Liverpool Telescope possible optical counterpart
  100. LIGO/Virgo/KAGRA S250211be: Identification of a GW compact binary merger candidate

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