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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"

6400 results found.

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

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