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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"

6094 results found.

  1. GRB 250327A: Fermi GBM observation
  2. Konus-Wind detection of GRB 250322A (short)
  3. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  4. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  5. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  6. GRB 250321B: Swift-XRT observations
  7. GRB 250322A: Swift-XRT refined Analysis
  8. GRB 250322A: NOT optical upper limits
  9. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  10. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  11. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  12. GRB 250320B: Fermi GBM Observation
  13. GRB 250321A: Swift-XRT refined Analysis
  14. GRB 250320B: Fermi-LAT detection
  15. EP250321a: Kinder optical follow-up observations
  16. EP250321a: Swift-XRT detection of an X-ray source
  17. EP250321a: TRT optical counterpart detection
  18. GRB 250321A: Swift-XRT localisation
  19. GRB 250321A: Fermi GBM Observation
  20. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  21. GRB 250317B: NOT optical observations suggest an optical plateau phase
  22. GRB 250317B: Swift-XRT observations
  23. GRB 250316A: Swift/UVOT Upper Limits
  24. EP 250317B: Fading optical counterpart detection by LCO
  25. GRB 250316A: Swift-XRT afterglow detection
  26. GRB 250317B: LCO detection of the fading optical afterglow
  27. GRB 250316A: Fermi GBM Observation
  28. GRB 250316A: Swift-XRT observations
  29. GRB 250314A: Swift/UVOT Upper Limits
  30. GRB 250314A: SVOM/VT upper limit
  31. GRB 250313A: Fermi GBM Detection
  32. GRB 250312B: Fermi GBM Observation
  33. GRB 250313A: Swift-XRT observations
  34. GRB 250313A: Fermi-LAT detection
  35. EP250302a: Chandra X-ray Detection
  36. GRB 250312A: Swift-XRT refined Analysis
  37. GRB 250226B: Fermi GBM Observation
  38. GRB 250302A: Fermi GBM Observation
  39. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  40. GRB 250223B: Fermi GBM Observation
  41. GRB 250311A: Swift-XRT observations
  42. GRB 250228A: Fermi GBM Observation
  43. GRB 250309B / AT2025dws: further SAO RAS optical observations
  44. Konus-Wind detection of GRB 250309B
  45. GRB 250309B: Swift-XRT refined Analysis
  46. GRB 250309B / IceCube-250309A: GECAM-B observations
  47. GRB 250309B / AT2025dws: SAO RAS optical observations
  48. GRB 250309B: Fermi GBM Observation
  49. Fermi GRB 250309A: Global MASTER-Net observations report
  50. Fermi-LAT gamma-ray observations of IceCube-250309A
  51. EP250308a: Einstein Probe detection of an X-ray transient
  52. EP250308a: NOT optical upper limit
  53. Fermi trigger No 762963055: Global MASTER-Net observations report
  54. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  55. EP250302a: Optical Observations at CrAO and SAO RAS
  56. EP250302A: 1.3m DFOT optical afterglow detection
  57. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  58. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  59. EP250304a: Swift-XRT detection of a fading X-ray source
  60. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  61. EP250302a: SAO RAS optical observations
  62. EP250302a: Kinder optical follow-up observations
  63. EP250302a: NUTTelA-TAO Early Measurments
  64. EP250302a: Swift-XRT observations of a fading X-ray source
  65. EP250228a: Optical observations with Kinder and Swift/UVOT
  66. Konus-Wind detection of GRB 250226A
  67. EP250227a: TRT optical upper limit
  68. GRB 250225B: VLT/HAWKI near-infrared observations
  69. EP250227a: Optical upper limits with Kinder observations
  70. GRB 250226A: Fermi GBM Observation
  71. EP250225a: EP-FXT follow-up observation
  72. GRB 250226A / EP250226a: LCO detection of the afterglow
  73. EP250225a: TRT optical upper limits
  74. EP250226a/GRB 250226A: 1.6m Mephisto observations
  75. EP250226a/GRB 250226A: Kinder optical follow-up observations
  76. GRB 250221A: EP-FXT detection of the X-ray afterglow
  77. EP250226a / GRB 250226A: TRT optical counterpart observation
  78. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  79. Fermi GRB 250226A: Global MASTER-Net observations report
  80. EP250223a: Kinder optical follow-up observations
  81. EP250223a: 1.6m Mephisto and 50cm array observations
  82. EP250223a: LCO detection of the afterglow
  83. EP250223a: NOT optical afterglow candidate
  84. Konus-Wind detection of GRB 250221A
  85. EP250220a: EP-FXT follow-up observations
  86. GRB 250221A: Swift-XRT refined Analysis
  87. GRB 250221A: 1.6m Mephisto optical detection
  88. EP250220a: 1.6m Mephisto observations
  89. EP250220a: Optical upper limit with Kinder observations
  90. GRB 250219A: Swift/UVOT Upper Limits
  91. GRB 250219A: NOT optical observations
  92. GRB 250219A: Swift-XRT observations
  93. Konus-Wind detection of GRB 250215A / EP250215a
  94. GRB 250217C: Swift-XRT observations
  95. GRB 250217C: Fermi GBM Observation
  96. GRB 250213A: Swift-XRT observations
  97. GRANDMA/OPD observations of GRB250215A
  98. GRB 250215A: Swift/UVOT Upper Limits
  99. GRB 250215A: Fermi GBM Observation
  100. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report

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