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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"

12332 results found.

  1. GRB 250207a: ATCA Radio Upper Limits
  2. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  3. EP250223a: REM NIR upper limit
  4. EP250223a: 1.6m Mephisto and 50cm array observations
  5. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  6. EP250223a: Global MASTER-Net observations report
  7. Fermi GRB 250223A: Global MASTER-Net observations report
  8. Fermi trigger No 762020305: Global MASTER-Net observations report
  9. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  10. EP250220a: FTW optical and NIR observations and upper limits
  11. EP250220a: EP-FXT follow-up observations
  12. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  13. Fermi trigger No 761805304: Global MASTER-Net observations report
  14. GRB 250221A: 1.6m Mephisto optical detection
  15. GRB 250221A: AKO Optical Upper Limit
  16. GRB 250221A: Swift/UVOT Detection
  17. EP250220a: Liverpool Telescope upper limits
  18. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  19. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  20. EP250220a: 1.6m Mephisto observations
  21. EP250220a: Liverpool Telescope optical upper limits
  22. EP250220a: Optical upper limit with Kinder observations
  23. Swift GRB250221.15: Global MASTER-Net OT detection
  24. Swift GRB250221.15: Global MASTER-Net observations report
  25. EP250220a: Xinglong optical upper limit
  26. EP250220a: Global MASTER-Net observations report
  27. GRB 250219A: Swift/UVOT Upper Limits
  28. GRB 250219A: OHP/T193 optical upper limit
  29. GRB 250219A: 1.6m Mephisto optical upper limits
  30. GRB 250219A: Swift-XRT observations
  31. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  32. GRB 250217C: Swift-XRT observations
  33. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  34. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  35. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  36. GRB 250213A: Swift-XRT observations
  37. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  38. Fermi GRB 250217C: Global MASTER-Net observations report
  39. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  40. Fermi GRB 250217A: Global MASTER-Net observations report
  41. GRANDMA/OPD observations of GRB250215A
  42. Fermi GRB 250216A: Global MASTER-Net observations report
  43. EP250212a: FTW optical and NIR upper limits
  44. GRB 250215A: Swift/UVOT Upper Limits
  45. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  46. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  47. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  48. EP250215a: Global MASTER-Net observations report
  49. Fermi GRB 250215A: Global MASTER-Net observations report
  50. Fermi trigger No 761206993: Global MASTER-Net observations report
  51. EP250207b: Xinglong optical upper limit
  52. Fermi GRB 250214A: Global MASTER-Net observations report
  53. EP250212a: Xinglong optical upper limit
  54. EP250212a: Global MASTER-Net observations report
  55. GRB 250205A: VIRT Optical Upper Limit
  56. GRB 250205A: Leavitt Observatory optical upper limit
  57. EP250207b: VLA radio upper limits
  58. EP250212a: Liverpool Telescope optical upper limits
  59. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  60. GRB250101A: Radio upper limits from GMRT observations
  61. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  62. Fermi GRB 250212A: Global MASTER-Net observations report
  63. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  64. Fermi trigger No 760945500: Global MASTER-Net observations report
  65. Integral GRB250211.89: Global MASTER-Net observations report
  66. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  67. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  68. Konus-Wind detection of GRB 250206A
  69. EP250207b: Global MASTER-Net observations report
  70. GRB 241128A: VIRT Optical Upper Limit
  71. EP250207A: Upper limits from Fermi-GBM Observations
  72. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  73. Fermi GRB 250210A: Global MASTER-Net observations report
  74. LIGO/Virgo/KAGRA S250206dm: Upper limits from GECAM Observations
  75. IceCube-250207A: Upper limits from a search for additional neutrino events in IceCube
  76. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  77. IceCube Alert 250207.09: Global MASTER-Net observations report
  78. LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: MASTER observations and possible mother galaxy
  79. Fermi-LAT Gamma-ray Observations of IceCube-250207A
  80. GRB 250206A: Swift-XRT observations
  81. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A BOOTES-5 and 2.2m CAHA optical upper limits
  82. GRB 250205A: 1.3m DFOT optical upper limit
  83. GRB 250207B: Swift-XRT observations
  84. 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%
  85. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits
  86. Konus-Wind detection of GRB 250204B
  87. IGO/Virgo/KAGRA S250206dm: Virtual Telescope Project upper limit for the Neutrino IceCube Candidate
  88. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limit for the Neutrino IceCube Candidate
  89. LIGO/Virgo/KAGRA S250206dm: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  90. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the AT 2025azn Optical Candidate
  91. GRB 250129A: Continued AbAO and Mondy optical observations
  92. LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
  93. GRB 250207B: MAXI/GSC detection
  94. LIGO/Virgo/KAGRA S250206dm: Upper limits from Fermi-GBM Observations
  95. Fermi-LAT Gamma-ray Observations of IceCube-250203A
  96. LIGO/Virgo/KAGRA S250206dm: Coverage and upper limits from MAXI/GSC observations
  97. GRB 250205A: REM NIR upper limit
  98. GRB 250205A: Swift/UVOT Upper Limits
  99. GRB 250205A: GOTO optical upper limits
  100. EP 250108A: Upper limits from Fermi-GBM Observations

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