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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"

929 results found.

  1. EP250508a: Einstein Probe detection of an X-ray transient
  2. GRB 250507A: follow-up observation with EP-FXT
  3. EP#01709175213/IGR J19566+0326: Swift-XRT detection
  4. EP-WXT trigger 01709175213: a new X-ray outburst of LMXB MAXI J1957+032
  5. SVOM/sb25050601: EP-FXT observations
  6. SVOM/sb25043004: EP-FXT observations
  7. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  8. EP 250427A: Optical counterpart detection by LCO.
  9. EP250428b: refined analysis of the EP-FXT follow-up observation
  10. EP250428b: SVOM/VT upper limit
  11. GRB 250427A: Swift/UVOT Detection
  12. EP250428b: Einstein Probe detection of a fast X-ray transient
  13. EP250427a: EP-FXT follow-up observations
  14. EP250427a: LT optical counterpart detection
  15. GRB 250427A: Swift-XRT refined Analysis
  16. EP250427a: Einstein Probe detection of a fast X-ray transient
  17. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  18. EP250421a: Einstein Probe detection of an X-ray transient
  19. EP250416a: refined EP-WXT and EP-FXT analysis
  20. EP250416a: Gemini South-GMOS optical counterpart
  21. EP250416a: GSP optical upper limit
  22. EP250416a: Einstein Probe detection of an X-ray transient
  23. EP250304a: ATCA radio observations
  24. EP250404a: Nanshan 0.43m Telescope optical observatios
  25. EP250407a: Swift-XRT observations
  26. GRB 250407A: EP-WXT afterglow detection
  27. EP250407a: EP-WXT detection of a fast X-ray transient
  28. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  29. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  30. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  31. EP250404a: refined analysis of the EP-WXT and EP-FXT observations
  32. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  33. EP250402a: Optical upper limit with PD 1.3m observations
  34. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  35. EP250404a: Seimei/TriCCS optical counterpart detection
  36. EP250404a: LAST detection of optical counterpart
  37. EP250404a: BOOTES-4/JGT optical afterglow detection
  38. EP250404a: Einstein Probe detection of an X-ray transient
  39. GRB 250402A: EP-FXT afterglow detection
  40. EP250402a: EP-FXT follow-up observations
  41. The EP-WXT trigger 01709133862 is a flaring star
  42. EP250402a: Einstein Probe detection of a fast X-ray transient
  43. FRB 20250316A: FTW optical observations
  44. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  45. The EP-WXT trigger 01709133021 (designated as EP250324a) is not a real source
  46. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  47. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  48. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  49. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  50. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  51. EP250321a: KAIT optical observations
  52. EP250321a: WFST optical observations
  53. EP 250321A: Optical counterpart detection by LCO.
  54. EP250321a: Swift-XRT detection of an X-ray source
  55. EP250321a: VLT/X-shooter redshift z = 4.368
  56. EP250321a: BOOTES-5/JGT optical afterglow detection
  57. EP250321a: Einstein Probe detection of an X-ray transient
  58. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  59. The EP-WXT trigger 01709132801 is likely a flaring star
  60. GRB 250314A: EP-FXT afterglow detection
  61. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  62. EP250315a: Einstein Probe detection of an X-ray transient
  63. EP250311a/GRB 250311A: Correction to EP-WXT detection time
  64. The EP-WXT trigger 01709132551 is not a real source
  65. EP250311a/GRB 250311A: EP-FXT follow-up observation
  66. EP250311a/GRB 250311A: EP-WXT detection
  67. The EP-WXT trigger 01709132425 is not a real source
  68. EP250308a: GSP optical upper limit
  69. EP250308a: Einstein Probe detection of an X-ray transient
  70. The EP-WXT trigger 01709132387 is likely a flaring star
  71. The EP-WXT trigger 01709132323 is likely a flaring star
  72. EP 250304A: Optical counterpart detection by LCO
  73. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  74. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  75. EP250304a: Swift-XRT detection of a fading X-ray source
  76. EP250304a: Einstein Probe detection of an X-ray transient
  77. The EP-WXT trigger 01709132212 is not a real source
  78. EP250302a: Swift/UVOT detection
  79. EP250302a: NUTTelA-TAO Early Measurments
  80. EP250302a: Einstein Probe detection of an X-ray transient
  81. EP250302a: SVOM/C-GFT optical observations
  82. EP250302a: Montarrenti Observatory optical detection
  83. EP250302a: Nanshan/HMT optical counterpart detection
  84. The EP-WXT trigger 01709132140 is likely a flaring star
  85. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  86. EP250227a: Einstein Probe detected of a fast X-ray transient
  87. EP250228a: updates on the EP observations
  88. EP250225a: EP-FXT follow-up observation
  89. EP250228a: Swift/XRT localisation
  90. EP250228a: Einstein Probe detection of an X-ray transient
  91. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  92. GRB 250221A: EP-FXT detection of the X-ray afterglow
  93. EP250226a/GRB 250226A: GSP detects optical counterpart
  94. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  95. EP250225a: GSP optical upper limit
  96. EP250225a: Einstein Probe detected of a fast X-ray transient
  97. GRB 250219A: EP-FXT afterglow detection
  98. EP250223a: refined analysis of the EP-WXT and FXT observations
  99. The EP-WXT trigger 01709131882 is likely a flaring star
  100. EP250223a: Swift/XRT localization

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