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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"

27561 results found.

  1. EP250302a: Xinglong F60B optical observation
  2. EP250302a: Swift-XRT observations of a fading X-ray source
  3. EP250302a: Einstein Probe detection of an X-ray transient
  4. GRB 250226A: GRANDMA Optical Observations
  5. EP250302a: Montarrenti Observatory optical detection
  6. EP250302a: FTW optical and NIR detection
  7. EP250302a: Nanshan/HMT optical counterpart detection
  8. IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
  9. GRB 250302A: Fermi GBM Final Real-time Localization
  10. GRB 250228A: Fermi GBM Final Localization
  11. GRB 250225B: VLT near-infrared afterglow confirmation
  12. EP250228a: Optical observations with Kinder and Swift/UVOT
  13. Konus-Wind detection of GRB 250226A
  14. GRB 250225B: EIRSAT-1 GMOD Detection
  15. GRB 250225B: VLT/HAWKI near-infrared observations
  16. EP250227a: Optical upper limits with Kinder observations
  17. EP250227a: Einstein Probe detected of a fast X-ray transient
  18. EP250228a: updates on the EP observations
  19. EP250225a: EP-FXT follow-up observation
  20. EP250223a: J band upper limit by SYSU 80cm telescope
  21. EP250228a: Swift/XRT localisation
  22. EP250228a: Einstein Probe detection of an X-ray transient
  23. GRB 250226A / EP250226a: LCO detection of the afterglow
  24. GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
  25. EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
  26. GRB 250225B: INTEGRAL SPI-ACS detection
  27. EP250226a / GRB 250226A: SVOM/VT optical observations
  28. EP250225a: TRT optical upper limits
  29. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  30. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  31. LIGO/Virgo/KAGRA S250227y: Retraction of GW compact binary merger candidate
  32. GRB 250226B: Fermi GBM Final Real-time Localization
  33. GRB 250221A: ATCA Detections and Upper Limits
  34. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  35. Konus-Wind detection of GRB 250225B
  36. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  37. GRB 250225B: VLT optical and near-infrared candidate counterpart
  38. GRB 250225B: VLT/FORS2 candidate optical afterglow
  39. GRB 250226A: GECAM-B detection
  40. GRB 250221A: EP-FXT detection of the X-ray afterglow
  41. EP250226a/GRB 250226A: GSP detects optical counterpart
  42. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  43. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  44. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  45. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  46. GRB 250226A: Fermi GBM Final Real-time Localization
  47. EP250225a: GSP optical upper limit
  48. EP250225a: Einstein Probe detected of a fast X-ray transient
  49. GRB 250225B: Swift detection of a burst
  50. EP250223a: GROWTH-India Telescope optical observations
  51. EP250215A: J band upper limit by SYSU 80cm telescope
  52. GRB 250225A: Fermi GBM Final Real-time Localization
  53. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  54. GRB 250207a: ATCA Radio Upper Limits
  55. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  56. GRB 250119B: VZLUSAT-2 detection
  57. GRB 250223C: Fermi GBM Final Real-time Localization
  58. GRB 250202B: VZLUSAT-2 detection
  59. GRB 250219A: EP-FXT afterglow detection
  60. EP250223a: GOTO optical afterglow detections
  61. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  62. GRB 250210A: VZLUSAT-2 detection
  63. GRB 250206A: VZLUSAT-2 detection
  64. EP250223a: REM NIR upper limit
  65. EP250223a: TRT optical afterglow observation
  66. EP250223a: refined analysis of the EP-WXT and FXT observations
  67. EP250223a: 1.6m Mephisto and 50cm array observations
  68. GRB 250221A: TNOT detection of the optical counterpart
  69. EP250223a: SVOM/VT optical observation
  70. 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
  71. EP250223a: OASDG optical observations
  72. EP250223a: LCO detection of the afterglow
  73. EP250223a: early optical detection by BOOTES-4
  74. EP250223a: NOT redshift z = 2.756
  75. EP250223a: Swift/XRT localization
  76. EP250223a: NOT optical afterglow candidate
  77. GRB 250223B: Fermi GBM Final Localization
  78. GRB 250221A: VLA radio detection
  79. GRB 250223A: Fermi GBM Final Real-time Localization
  80. EP250223a: Einstein Probe detection of an X-ray transient
  81. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  82. GRB 250221A: continued Mondy optical observations, brightening afterglow
  83. GRB 250221A: Optical counterpart detection by LCO.
  84. GRB 250221A: Mondy optical observations
  85. Konus-Wind detection of GRB 250221A
  86. GRB 250221A: Assy optical observations
  87. EP250220a: EP-FXT follow-up observations
  88. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  89. GRB 250221A: VLT/X-shooter redshift z = 0.768
  90. GRB 250221A: GRANDMA/TAROT Detection
  91. GRB 250221A: Swift-XRT refined Analysis
  92. GRB 250221A: NOT optical observations
  93. GRB 250221A: 1.6m Mephisto optical detection
  94. GRB 250221A: AKO Optical Upper Limit
  95. GRB 250221A: Swift/UVOT Detection
  96. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  97. GRB 250221A: REM optical/NIR afterglow detection
  98. GRB 250221A: Enhanced Swift-XRT position
  99. EP250220a: Liverpool Telescope optical upper limits
  100. EP250220a: Optical upper limit with Kinder observations

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