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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"

28079 results found.

  1. GRB 250306A: Swift detection of a burst
  2. LIGO/Virgo/KAGRA S250306ej: Retraction of GW compact binary merger candidate
  3. GRB 250305A: Fermi GBM Final Real-time Localization
  4. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  5. EP 250304A: Optical counterpart detection by LCO
  6. EP250302A: 1.3m DFOT optical afterglow detection
  7. Konus-Wind detection of GRB 250222A
  8. EP250304a: REM NIR upper limits
  9. IPN triangulation of GRB 250222A
  10. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  11. EP250304a: Swift-XRT detection of a fading X-ray source
  12. EP250304a: TRT optical counterpart detection
  13. EP250304a: Einstein Probe detection of an X-ray transient
  14. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  15. EP250225a: the candidate optical counterpart is an AGN
  16. EP250302a: Swift/UVOT detection
  17. EP250302a: NUTTelA-TAO Early Measurments
  18. EP250302a: REM NIR upper limits
  19. EP250302a: Xinglong F60B optical observation
  20. EP250302a: Swift-XRT observations of a fading X-ray source
  21. EP250302a: Einstein Probe detection of an X-ray transient
  22. GRB 250226A: GRANDMA Optical Observations
  23. EP250302a: Montarrenti Observatory optical detection
  24. EP250302a: FTW optical and NIR detection
  25. EP250302a: Nanshan/HMT optical counterpart detection
  26. IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
  27. GRB 250302A: Fermi GBM Final Real-time Localization
  28. GRB 250228A: Fermi GBM Final Localization
  29. GRB 250225B: VLT near-infrared afterglow confirmation
  30. EP250228a: Optical observations with Kinder and Swift/UVOT
  31. Konus-Wind detection of GRB 250226A
  32. GRB 250225B: EIRSAT-1 GMOD Detection
  33. GRB 250225B: VLT/HAWKI near-infrared observations
  34. EP250227a: Optical upper limits with Kinder observations
  35. EP250227a: Einstein Probe detected of a fast X-ray transient
  36. EP250228a: updates on the EP observations
  37. EP250225a: EP-FXT follow-up observation
  38. EP250223a: J band upper limit by SYSU 80cm telescope
  39. EP250228a: Swift/XRT localisation
  40. EP250228a: Einstein Probe detection of an X-ray transient
  41. GRB 250226A / EP250226a: LCO detection of the afterglow
  42. GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
  43. EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
  44. GRB 250225B: INTEGRAL SPI-ACS detection
  45. EP250226a / GRB 250226A: SVOM/VT optical observations
  46. EP250225a: TRT optical upper limits
  47. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  48. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  49. LIGO/Virgo/KAGRA S250227y: Retraction of GW compact binary merger candidate
  50. GRB 250226B: Fermi GBM Final Real-time Localization
  51. GRB 250221A: ATCA Detections and Upper Limits
  52. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  53. Konus-Wind detection of GRB 250225B
  54. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  55. GRB 250225B: VLT optical and near-infrared candidate counterpart
  56. GRB 250225B: VLT/FORS2 candidate optical afterglow
  57. GRB 250226A: GECAM-B detection
  58. GRB 250221A: EP-FXT detection of the X-ray afterglow
  59. EP250226a/GRB 250226A: GSP detects optical counterpart
  60. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  61. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  62. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  63. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  64. GRB 250226A: Fermi GBM Final Real-time Localization
  65. EP250225a: GSP optical upper limit
  66. EP250225a: Einstein Probe detected of a fast X-ray transient
  67. GRB 250225B: Swift detection of a burst
  68. EP250223a: GROWTH-India Telescope optical observations
  69. EP250215A: J band upper limit by SYSU 80cm telescope
  70. GRB 250225A: Fermi GBM Final Real-time Localization
  71. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  72. GRB 250207a: ATCA Radio Upper Limits
  73. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  74. GRB 250119B: VZLUSAT-2 detection
  75. GRB 250223C: Fermi GBM Final Real-time Localization
  76. GRB 250202B: VZLUSAT-2 detection
  77. GRB 250219A: EP-FXT afterglow detection
  78. EP250223a: GOTO optical afterglow detections
  79. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  80. GRB 250210A: VZLUSAT-2 detection
  81. GRB 250206A: VZLUSAT-2 detection
  82. EP250223a: REM NIR upper limit
  83. EP250223a: TRT optical afterglow observation
  84. EP250223a: refined analysis of the EP-WXT and FXT observations
  85. EP250223a: 1.6m Mephisto and 50cm array observations
  86. GRB 250221A: TNOT detection of the optical counterpart
  87. EP250223a: SVOM/VT optical observation
  88. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO trigger with ID 762004910: Identification of a GW compact binary merger candidate possibly associated with a sub-threshold Swift/BAT-GUANO trigger
  89. EP250223a: OASDG optical observations
  90. EP250223a: LCO detection of the afterglow
  91. EP250223a: early optical detection by BOOTES-4
  92. EP250223a: NOT redshift z = 2.756
  93. EP250223a: Swift/XRT localization
  94. EP250223a: NOT optical afterglow candidate
  95. GRB 250223B: Fermi GBM Final Localization
  96. GRB 250221A: VLA radio detection
  97. GRB 250223A: Fermi GBM Final Real-time Localization
  98. EP250223a: Einstein Probe detection of an X-ray transient
  99. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  100. GRB 250221A: continued Mondy optical observations, brightening afterglow

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