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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 250221A: GRANDMA/TAROT Detection
  2. GRB 250221A: 1.6m Mephisto optical detection
  3. GRB 250221A: AKO Optical Upper Limit
  4. GRB 250221A: Swift/UVOT Detection
  5. EP250220a: Liverpool Telescope upper limits
  6. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  7. GRB 250221A: REM optical/NIR afterglow detection
  8. GRB 250221A: Enhanced Swift-XRT position
  9. EP250220a: 1.6m Mephisto observations
  10. EP250220a: Liverpool Telescope optical upper limits
  11. EP250220a: Optical upper limit with Kinder observations
  12. SVOM trigger sb25022102 is not an astrophysical event
  13. SVOM/sb25022102: SVOM detection of an X-ray transient
  14. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  15. GRB 250221A: Swift detection of a burst with an optical counterpart
  16. EP250220a: Xinglong optical upper limit
  17. GRB 250219A: Swift/UVOT Upper Limits
  18. GRB 250219A: OHP/T193 optical upper limit
  19. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  20. GRB 250219A: 1.6m Mephisto optical upper limits
  21. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  22. GRB 250219A: Swift ToO observations
  23. GRB 250219A: SVOM detection of a burst
  24. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  25. GRB 250217C: Swift-XRT observations
  26. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  27. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  28. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  29. GRB 250217C: SVOM/GRM observation
  30. GRB 250217C: Tiled Swift observations
  31. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  32. SVOM/sb25021804: SVOM detection of a long X-ray transient
  33. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  34. GRANDMA/OPD observations of GRB250215A
  35. GRB 250215A / EP250215a: LCO detection of the afterglow
  36. GRB 250215A: Swift/UVOT Upper Limits
  37. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  38. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  39. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  40. GRB 250215A: SVOM/GRM observation
  41. EP250215a / GRB 250215A: AstroSat CZTI detection
  42. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  43. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  44. EP250207b: Xinglong optical upper limit
  45. GRB 250213A: Swift ToO observations
  46. EP250212a: Xinglong optical upper limit
  47. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  48. GRB 250213A: SVOM detection of a burst
  49. GRB 250205A: VIRT Optical Upper Limit
  50. GRB 250205A: Leavitt Observatory optical upper limit
  51. EP250207B: Chandra localization of the X-ray counterpart
  52. EP250212a: Liverpool Telescope optical upper limits
  53. GRB250101A: Radio upper limits from GMRT observations
  54. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  55. EP250207B: GTC z-band Observations
  56. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  57. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  58. EP250207b: NOT optical counterpart candidate
  59. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  60. GRB 250211A: Swift ToO observations
  61. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  62. GRB 250206A: Fermi GBM Observation
  63. GRB 250205A / EP250205A: radio detection with the VLA
  64. EP250207b: Tentative z-band brightening source
  65. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  66. GRB 250210A: SVOM/GRM observation of a long burst
  67. EP250207b: Liverpool Telescope possible optical counterpart
  68. LIGO/Virgo/KAGRA S250211aa: Identification of a GW compact binary merger candidate
  69. GRB 250207A: Skynet optical afterglow observations
  70. GRB 241128A: VIRT Optical Upper Limit
  71. EP250207b: Gemini GMOS-N z-band observations
  72. EP250207b: a new X-ray transient detected by Einstein Probe
  73. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  74. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  75. LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
  76. Fermi-LAT Gamma-ray Observations of IceCube-250207A
  77. GRB 250207A: 1.3m DFOT Optical observations
  78. LIGO/Virgo/KAGRA S250206dm: WFST follow-up observations
  79. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A BOOTES-5 and 2.2m CAHA optical upper limits
  80. GRB 250129A: GRANDMA Continued Afterglow Detection
  81. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  82. GRB 250205A: 1.3m DFOT optical upper limit
  83. GRB 250206A: Tiled Swift observations
  84. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
  85. GRB 250207B: Swift-XRT observations
  86. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates
  87. GRB 250208A: Fermi GBM Final Real-time Localization
  88. LIGO/Virgo/KAGRA S250208ad: Identification of a GW compact binary merger candidate
  89. EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
  90. GRB 250207A: Enhanced Swift-XRT position
  91. CHIME/FRB source FRB 20250206A detected less than 1 minute after LIGO-Virgo-Kagra (LVK) S250206dm, however the probability of spatial coincidence is order 0.1%
  92. GRB 250129A: ABObservatory SLOAN r’ afterglow detection
  93. GRB 250207A: REM IR afterglow detection
  94. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits
  95. GRB 250207B: Tiled Swift observations
  96. IGO/Virgo/KAGRA S250206dm: Virtual Telescope Project upper limit for the Neutrino IceCube Candidate
  97. GRB 250207A: REM optical afterglow detection
  98. GRB 250207A: Swift/UVOT Detection
  99. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limit for the Neutrino IceCube Candidate
  100. LIGO/Virgo/KAGRA S250206dm: GOTO observations of optical candidates AT 2025azn and AT 2025azm

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