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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"

24601 results found.

  1. EP250220a: Liverpool Telescope upper limits
  2. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  3. GRB 250221A: REM optical/NIR afterglow detection
  4. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  5. GRB 250221A: Enhanced Swift-XRT position
  6. EP250220a: 1.6m Mephisto observations
  7. EP250220a: Liverpool Telescope optical upper limits
  8. EP250220a: Optical upper limit with Kinder observations
  9. SVOM trigger sb25022102 is not an astrophysical event
  10. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  11. GRB 250221A: Swift detection of a burst with an optical counterpart
  12. Swift GRB250221.15: Global MASTER-Net OT detection
  13. EP250220a: Xinglong optical upper limit
  14. GRB 250219A: Swift/UVOT Upper Limits
  15. GRB 250219A: OHP/T193 optical upper limit
  16. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  17. GRB 250219A: 1.6m Mephisto optical upper limits
  18. GRB 250219A: Swift-XRT observations
  19. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  20. Konus-Wind detection of GRB 250215A / EP250215a
  21. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  22. GRB 250217C: Swift-XRT observations
  23. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  24. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  25. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  26. GRB 250217C: SVOM/GRM observation
  27. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  28. SVOM/sb25021804: SVOM detection of a long X-ray transient
  29. GRB 250213A: Swift-XRT observations
  30. GRB 250216A: AstroSat CZTI detection
  31. GRB 250217C: AstroSat CZTI detection of a short burst
  32. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  33. GRANDMA/OPD observations of GRB250215A
  34. GRB 250215A / EP250215a: LCO detection of the afterglow
  35. GRB 250215A: Swift/UVOT Upper Limits
  36. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  37. GRB 250215A: Fermi GBM Observation
  38. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  39. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  40. GRB 250215A: Swift-XRT refined Analysis
  41. GRB 250215A: SVOM/GRM observation
  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. EP250212a: Xinglong optical upper limit
  46. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  47. EP250212a: Global MASTER-Net observations report
  48. GRB 250205A: VIRT Optical Upper Limit
  49. GRB 250205A: Leavitt Observatory optical upper limit
  50. EP250207B: Chandra localization of the X-ray counterpart
  51. EP250212a: Liverpool Telescope optical upper limits
  52. GRB250101A: Radio upper limits from GMRT observations
  53. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  54. EP250207B: GTC z-band Observations
  55. Fermi GRB 250212A: Global MASTER-Net observations report
  56. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  57. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  58. Fermi trigger No 760945500: Global MASTER-Net observations report
  59. EP250207b: NOT optical counterpart candidate
  60. GRB 250211B: A long GRB detected by INTEGRAL
  61. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  62. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  63. LIGO/Virgo/KAGRA S250211be: Updated Sky localization
  64. GRB 250207A: Fermi GBM Observation
  65. GRB 250206A: Fermi GBM Observation
  66. GRB 250205A / EP250205A: radio detection with the VLA
  67. EP250207b: Tentative z-band brightening source
  68. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  69. Konus-Wind detection of GRB 250206A
  70. GRB 250210A: SVOM/GRM observation of a long burst
  71. EP250207b: Liverpool Telescope possible optical counterpart
  72. LIGO/Virgo/KAGRA S250211be: Identification of a GW compact binary merger candidate
  73. LIGO/Virgo/KAGRA S250211aa: Updated Sky localization and EM Bright Classification
  74. LIGO/Virgo/KAGRA S250211aa: Identification of a GW compact binary merger candidate
  75. GRB 250207A: Skynet optical afterglow observations
  76. GRB 241128A: VIRT Optical Upper Limit
  77. EP250207b: Gemini GMOS-N z-band observations
  78. EP250207A: Upper limits from Fermi-GBM Observations
  79. EP250207b: a new X-ray transient detected by Einstein Probe
  80. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  81. LIGO/Virgo/KAGRA S250206dm: Upper limits from GECAM Observations
  82. IceCube-250207A: Upper limits from a search for additional neutrino events in IceCube
  83. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  84. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  85. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  86. LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
  87. Fermi-LAT Gamma-ray Observations of IceCube-250207A
  88. GRB 250207A: 1.3m DFOT Optical observations
  89. LIGO/Virgo/KAGRA S250206dm: WFST follow-up observations
  90. GRB 250206A: Swift-XRT observations
  91. GRB 250129A: GRANDMA Continued Afterglow Detection
  92. GRB 250207A: Swift-BAT refined analysis
  93. LIGO/Virgo/KAGRA S250206dm: further Pan-STARRS observations and one candidate AT2025bbo
  94. LIGO/Virgo/KAGRA S250207bg: Updated NED Galaxies in the Localization Volume
  95. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  96. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  97. GRB 250205A: 1.3m DFOT optical upper limit
  98. LIGO/Virgo/KAGRA S250118az: Updated Sky localization
  99. LIGO/Virgo/KAGRA S250208ad: Updated Sky localization
  100. GRB 250206A: EIRSAT-1 GMOD Detection

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