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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.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

6797 results found.

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

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