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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"

12321 results found.

  1. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  2. Fermi trigger No 761805304: Global MASTER-Net observations report
  3. GRB 250221A: 1.6m Mephisto optical detection
  4. GRB 250221A: AKO Optical Upper Limit
  5. GRB 250221A: Swift/UVOT Detection
  6. EP250220a: Liverpool Telescope upper limits
  7. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  8. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  9. EP250220a: 1.6m Mephisto observations
  10. EP250220a: Liverpool Telescope optical upper limits
  11. EP250220a: Optical upper limit with Kinder observations
  12. Swift GRB250221.15: Global MASTER-Net OT detection
  13. Swift GRB250221.15: Global MASTER-Net observations report
  14. EP250220a: Xinglong optical upper limit
  15. EP250220a: Global MASTER-Net observations report
  16. GRB 250219A: Swift/UVOT Upper Limits
  17. GRB 250219A: OHP/T193 optical upper limit
  18. GRB 250219A: 1.6m Mephisto optical upper limits
  19. GRB 250219A: Swift-XRT observations
  20. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  21. GRB 250217C: Swift-XRT observations
  22. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  23. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  24. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  25. GRB 250213A: Swift-XRT observations
  26. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  27. Fermi GRB 250217C: Global MASTER-Net observations report
  28. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  29. Fermi GRB 250217A: Global MASTER-Net observations report
  30. GRANDMA/OPD observations of GRB250215A
  31. Fermi GRB 250216A: Global MASTER-Net observations report
  32. EP250212a: FTW optical and NIR upper limits
  33. GRB 250215A: Swift/UVOT Upper Limits
  34. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  35. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  36. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  37. EP250215a: Global MASTER-Net observations report
  38. Fermi GRB 250215A: Global MASTER-Net observations report
  39. Fermi trigger No 761206993: Global MASTER-Net observations report
  40. EP250207b: Xinglong optical upper limit
  41. Fermi GRB 250214A: Global MASTER-Net observations report
  42. EP250212a: Xinglong optical upper limit
  43. EP250212a: Global MASTER-Net observations report
  44. GRB 250205A: VIRT Optical Upper Limit
  45. GRB 250205A: Leavitt Observatory optical upper limit
  46. EP250207b: VLA radio upper limits
  47. EP250212a: Liverpool Telescope optical upper limits
  48. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  49. GRB250101A: Radio upper limits from GMRT observations
  50. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  51. Fermi GRB 250212A: Global MASTER-Net observations report
  52. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  53. Fermi trigger No 760945500: Global MASTER-Net observations report
  54. Integral GRB250211.89: Global MASTER-Net observations report
  55. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  56. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  57. Konus-Wind detection of GRB 250206A
  58. EP250207b: Global MASTER-Net observations report
  59. GRB 241128A: VIRT Optical Upper Limit
  60. EP250207A: Upper limits from Fermi-GBM Observations
  61. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  62. Fermi GRB 250210A: Global MASTER-Net observations report
  63. LIGO/Virgo/KAGRA S250206dm: Upper limits from GECAM Observations
  64. IceCube-250207A: Upper limits from a search for additional neutrino events in IceCube
  65. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  66. IceCube Alert 250207.09: Global MASTER-Net observations report
  67. LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: MASTER observations and possible mother galaxy
  68. Fermi-LAT Gamma-ray Observations of IceCube-250207A
  69. GRB 250206A: Swift-XRT observations
  70. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A BOOTES-5 and 2.2m CAHA optical upper limits
  71. GRB 250205A: 1.3m DFOT optical upper limit
  72. GRB 250207B: Swift-XRT observations
  73. 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%
  74. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits
  75. Konus-Wind detection of GRB 250204B
  76. IGO/Virgo/KAGRA S250206dm: Virtual Telescope Project upper limit for the Neutrino IceCube Candidate
  77. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limit for the Neutrino IceCube Candidate
  78. LIGO/Virgo/KAGRA S250206dm: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  79. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the AT 2025azn Optical Candidate
  80. GRB 250129A: Continued AbAO and Mondy optical observations
  81. LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
  82. GRB 250207B: MAXI/GSC detection
  83. LIGO/Virgo/KAGRA S250206dm: Upper limits from Fermi-GBM Observations
  84. Fermi-LAT Gamma-ray Observations of IceCube-250203A
  85. LIGO/Virgo/KAGRA S250206dm: Coverage and upper limits from MAXI/GSC observations
  86. GRB 250205A: REM NIR upper limit
  87. GRB 250205A: Swift/UVOT Upper Limits
  88. GRB 250205A: GOTO optical upper limits
  89. EP 250108A: Upper limits from Fermi-GBM Observations
  90. GRB 250129A: 7DT Detection and Medium-band SED of Afterglow
  91. Swift GRB250129A: MASTER 4 days observations report
  92. LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations
  93. EP250108A / SN 2025kg: Upper limits from a neutrino search with IceCube
  94. GRB 250127A: EP-FXT second observation epoch and confirmation of the x-ray afterglow fading
  95. GRB 250128B: SAO RAS Zeiss-1000 and CrAO ZTSh optical upper limits
  96. GRB 250128B: VLA radio upper limit
  97. Ep250125A: 1.3m DFOT optical upper limit
  98. GRB 250128B: TNG optical upper limit
  99. GRB 250127A: CrAO and Terskol optical upper limits
  100. GRB 250128B: NOT optical upper limit

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