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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"

1095 results found.

  1. EP250404a: Seimei/TriCCS optical counterpart detection
  2. EP250404a: LAST detection of optical counterpart
  3. EP250404a: BOOTES-4/JGT optical afterglow detection
  4. EP250404a: Einstein Probe detection of an X-ray transient
  5. GRB 250402A: EP-FXT afterglow detection
  6. EP250402a: EP-FXT follow-up observations
  7. The EP-WXT trigger 01709133862 is a flaring star
  8. EP250402a: Einstein Probe detection of a fast X-ray transient
  9. FRB 20250316A: FTW optical observations
  10. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  11. The EP-WXT trigger 01709133021 (designated as EP250324a) is not a real source
  12. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  13. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  14. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  15. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  16. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  17. EP250321a: KAIT optical observations
  18. EP250321a: WFST optical observations
  19. EP 250321A: Optical counterpart detection by LCO.
  20. EP250321a: Swift-XRT detection of an X-ray source
  21. EP250321a: VLT/X-shooter redshift z = 4.368
  22. EP250321a: BOOTES-5/JGT optical afterglow detection
  23. EP250321a: Einstein Probe detection of an X-ray transient
  24. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  25. The EP-WXT trigger 01709132801 is likely a flaring star
  26. GRB 250314A: EP-FXT afterglow detection
  27. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  28. EP250315a: Einstein Probe detection of an X-ray transient
  29. EP250311a/GRB 250311A: Correction to EP-WXT detection time
  30. The EP-WXT trigger 01709132551 is not a real source
  31. EP250311a/GRB 250311A: EP-FXT follow-up observation
  32. EP250311a/GRB 250311A: EP-WXT detection
  33. The EP-WXT trigger 01709132425 is not a real source
  34. EP250308a: GSP optical upper limit
  35. EP250308a: Einstein Probe detection of an X-ray transient
  36. The EP-WXT trigger 01709132387 is likely a flaring star
  37. The EP-WXT trigger 01709132323 is likely a flaring star
  38. EP 250304A: Optical counterpart detection by LCO
  39. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  40. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  41. EP250304a: Swift-XRT detection of a fading X-ray source
  42. EP250304a: Einstein Probe detection of an X-ray transient
  43. The EP-WXT trigger 01709132212 is not a real source
  44. EP250302a: Swift/UVOT detection
  45. EP250302a: NUTTelA-TAO Early Measurments
  46. EP250302a: Einstein Probe detection of an X-ray transient
  47. EP250302a: SVOM/C-GFT optical observations
  48. EP250302a: Montarrenti Observatory optical detection
  49. EP250302a: Nanshan/HMT optical counterpart detection
  50. The EP-WXT trigger 01709132140 is likely a flaring star
  51. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  52. EP250227a: Einstein Probe detected of a fast X-ray transient
  53. EP250228a: updates on the EP observations
  54. EP250225a: EP-FXT follow-up observation
  55. EP250228a: Swift/XRT localisation
  56. EP250228a: Einstein Probe detection of an X-ray transient
  57. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  58. GRB 250221A: EP-FXT detection of the X-ray afterglow
  59. EP250226a/GRB 250226A: GSP detects optical counterpart
  60. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  61. EP250225a: GSP optical upper limit
  62. EP250225a: Einstein Probe detected of a fast X-ray transient
  63. GRB 250219A: EP-FXT afterglow detection
  64. EP250223a: refined analysis of the EP-WXT and FXT observations
  65. The EP-WXT trigger 01709131882 is likely a flaring star
  66. EP250223a: Swift/XRT localization
  67. EP250223a: Einstein Probe detection of an X-ray transient
  68. EP250220a: EP-FXT follow-up observations
  69. EP250220a: EP-WXT detection of a fast X-ray transient
  70. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  71. The EP-WXT trigger 01709131775 is likely a flaring star
  72. GRB 250215A / EP250215a: LCO detection of the afterglow
  73. GRB 250215A: Swift/UVOT Upper Limits
  74. GRB 250215A: Swift-XRT refined Analysis
  75. EP250215A/GRB 250215A: INTEGRAL SPI-ACS detection
  76. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  77. EP250207b: VLA radio upper limits
  78. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  79. EP250207b: Liverpool Telescope possible optical counterpart
  80. EP250207b: Gemini GMOS-N z-band observations
  81. EP250207b: a new X-ray transient detected by Einstein Probe
  82. EP250207a: EP-WXT detection and XRT follow-up observation
  83. The EP-WXT trigger 01709131347 is likely a flaring star
  84. The EP-WXT trigger 01709131332 is likely a flaring star
  85. The EP-WXT trigger 01709131290 is likely a flaring star
  86. GRB 250205A: REM NIR upper limit
  87. EP250205a/GRB 250205A: correction to the source localization
  88. EP250205a/GRB 250205A: Einstein Probe observation
  89. The EP-WXT trigger 01709131196 is likely a flaring star
  90. The EP-WXT trigger 01709131153 is not a real source
  91. EP250108A / SN 2025kg: Upper limits from a neutrino search with IceCube
  92. GRB 250127A: EP-FXT second observation epoch and confirmation of the x-ray afterglow fading
  93. The EP-WXT trigger 01709131085 is likely a flaring star
  94. GRB 250127A: Swift-XRT observations
  95. GRB 250127A: EP-FXT afterglow detection
  96. EP250108a / SN 2025kg: Refined Analysis of EP-WXT Detection
  97. EP250125a: REM optical counterpart detection
  98. EP250125a: Swift/XRT detection of a fading counterpart
  99. EP250125a: a new X-ray transient detected by Einstein Probe
  100. The EP-WXT trigger 01709130758 is a false trigger

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