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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"

24603 results found.

  1. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  2. GRB 250221A: GRANDMA/TAROT Detection
  3. GRB 250221A: Swift-XRT refined Analysis
  4. GRB 250221A: NOT optical observations
  5. GRB 250221A: 1.6m Mephisto optical detection
  6. GRB 250221A: AKO Optical Upper Limit
  7. GRB 250221A: Swift/UVOT Detection
  8. EP250220a: Liverpool Telescope upper limits
  9. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  10. GRB 250221A: REM optical/NIR afterglow detection
  11. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  12. GRB 250221A: Enhanced Swift-XRT position
  13. EP250220a: 1.6m Mephisto observations
  14. EP250220a: Liverpool Telescope optical upper limits
  15. EP250220a: Optical upper limit with Kinder observations
  16. SVOM trigger sb25022102 is not an astrophysical event
  17. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  18. GRB 250221A: Swift detection of a burst with an optical counterpart
  19. Swift GRB250221.15: Global MASTER-Net OT detection
  20. EP250220a: Xinglong optical upper limit
  21. GRB 250219A: Swift/UVOT Upper Limits
  22. GRB 250219A: OHP/T193 optical upper limit
  23. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  24. GRB 250219A: 1.6m Mephisto optical upper limits
  25. GRB 250219A: Swift-XRT observations
  26. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  27. Konus-Wind detection of GRB 250215A / EP250215a
  28. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  29. GRB 250217C: Swift-XRT observations
  30. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  31. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  32. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  33. GRB 250217C: SVOM/GRM observation
  34. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  35. SVOM/sb25021804: SVOM detection of a long X-ray transient
  36. GRB 250213A: Swift-XRT observations
  37. GRB 250216A: AstroSat CZTI detection
  38. GRB 250217C: AstroSat CZTI detection of a short burst
  39. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  40. GRANDMA/OPD observations of GRB250215A
  41. GRB 250215A / EP250215a: LCO detection of the afterglow
  42. GRB 250215A: Swift/UVOT Upper Limits
  43. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  44. GRB 250215A: Fermi GBM Observation
  45. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  46. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  47. GRB 250215A: Swift-XRT refined Analysis
  48. GRB 250215A: SVOM/GRM observation
  49. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  50. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  51. EP250207b: Xinglong optical upper limit
  52. EP250212a: Xinglong optical upper limit
  53. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  54. EP250212a: Global MASTER-Net observations report
  55. GRB 250205A: VIRT Optical Upper Limit
  56. GRB 250205A: Leavitt Observatory optical upper limit
  57. EP250207B: Chandra localization of the X-ray counterpart
  58. EP250212a: Liverpool Telescope optical upper limits
  59. GRB250101A: Radio upper limits from GMRT observations
  60. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  61. EP250207B: GTC z-band Observations
  62. Fermi GRB 250212A: Global MASTER-Net observations report
  63. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  64. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  65. Fermi trigger No 760945500: Global MASTER-Net observations report
  66. EP250207b: NOT optical counterpart candidate
  67. GRB 250211B: A long GRB detected by INTEGRAL
  68. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  69. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  70. LIGO/Virgo/KAGRA S250211be: Updated Sky localization
  71. GRB 250207A: Fermi GBM Observation
  72. GRB 250206A: Fermi GBM Observation
  73. GRB 250205A / EP250205A: radio detection with the VLA
  74. EP250207b: Tentative z-band brightening source
  75. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  76. Konus-Wind detection of GRB 250206A
  77. GRB 250210A: SVOM/GRM observation of a long burst
  78. EP250207b: Liverpool Telescope possible optical counterpart
  79. LIGO/Virgo/KAGRA S250211be: Identification of a GW compact binary merger candidate
  80. LIGO/Virgo/KAGRA S250211aa: Updated Sky localization and EM Bright Classification
  81. LIGO/Virgo/KAGRA S250211aa: Identification of a GW compact binary merger candidate
  82. GRB 250207A: Skynet optical afterglow observations
  83. GRB 241128A: VIRT Optical Upper Limit
  84. EP250207b: Gemini GMOS-N z-band observations
  85. EP250207A: Upper limits from Fermi-GBM Observations
  86. EP250207b: a new X-ray transient detected by Einstein Probe
  87. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  88. LIGO/Virgo/KAGRA S250206dm: Upper limits from GECAM Observations
  89. IceCube-250207A: Upper limits from a search for additional neutrino events in IceCube
  90. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  91. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  92. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  93. LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
  94. Fermi-LAT Gamma-ray Observations of IceCube-250207A
  95. GRB 250207A: 1.3m DFOT Optical observations
  96. LIGO/Virgo/KAGRA S250206dm: WFST follow-up observations
  97. GRB 250206A: Swift-XRT observations
  98. GRB 250129A: GRANDMA Continued Afterglow Detection
  99. GRB 250207A: Swift-BAT refined analysis
  100. LIGO/Virgo/KAGRA S250206dm: further Pan-STARRS observations and one candidate AT2025bbo

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