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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"
  1. EP250223a: OASDG optical observations
  2. EP250223a: LCO detection of the afterglow
  3. EP250223a: early optical detection by BOOTES-4
  4. EP250223a: NOT redshift z = 2.756
  5. EP250223a: Swift/XRT localization
  6. EP250223a: NOT optical afterglow candidate
  7. GRB 250223B: Fermi GBM Final Localization
  8. EP250223a: Global MASTER-Net observations report
  9. GRB 250221A: VLA radio detection
  10. Fermi GRB 250223A: Global MASTER-Net observations report
  11. Fermi trigger No 762020305: Global MASTER-Net observations report
  12. GRB 250223A: Fermi GBM Final Real-time Localization
  13. EP250223a: Einstein Probe detection of an X-ray transient
  14. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  15. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  16. GRB 250221A: continued Mondy optical observations, brightening afterglow
  17. GRB 250221A: Optical counterpart detection by LCO.
  18. GRB 250221A: Mondy optical observations
  19. Konus-Wind detection of GRB 250221A
  20. GRB 250221A: Assy optical observations
  21. EP250220a: FTW optical and NIR observations and upper limits
  22. EP250220a: EP-FXT follow-up observations
  23. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  24. GRB 250221A: VLT/X-shooter redshift z = 0.768
  25. GRB 250221A: GRANDMA/TAROT Detection
  26. Fermi trigger No 761805304: Global MASTER-Net observations report
  27. Fermi Gamma-ray Burst Monitor trigger 761867337/250221909 is not a GRB
  28. GRB 250221A: Swift-XRT refined Analysis
  29. GRB 250221A: NOT optical observations
  30. GRB 250221A: 1.6m Mephisto optical detection
  31. LIGO/Virgo/KAGRA S250221gb: Retraction of GW compact binary merger candidate
  32. GRB 250221A: AKO Optical Upper Limit
  33. GRB 250221A: Swift/UVOT Detection
  34. EP250220a: Liverpool Telescope upper limits
  35. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  36. GRB 250221A: REM optical/NIR afterglow detection
  37. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  38. GRB 250221A: Enhanced Swift-XRT position
  39. LIGO/Virgo/KAGRA S250221eb: Retraction of GW compact binary merger candidate
  40. EP250220a: 1.6m Mephisto observations
  41. EP250220a: Liverpool Telescope optical upper limits
  42. EP250220a: Optical upper limit with Kinder observations
  43. SVOM trigger sb25022102 is not an astrophysical event
  44. SVOM/sb25022102: SVOM detection of an X-ray transient
  45. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  46. GRB 250221A: Swift detection of a burst with an optical counterpart
  47. Swift GRB250221.15: Global MASTER-Net OT detection
  48. Swift GRB250221.15: Global MASTER-Net observations report
  49. EP250220a: Xinglong optical upper limit
  50. Fermi Gamma-ray Burst Monitor trigger 761788229/250220993 is not a GRB
  51. GRB 250220B: Fermi GBM Final Real-time Localization
  52. Fermi Gamma-ray Burst Monitor trigger 761782146/250220923 is not a GRB
  53. GRB 250220A: Fermi GBM Final Real-time Localization
  54. EP250220a: Global MASTER-Net observations report
  55. EP250220a: EP-WXT detection of a fast X-ray transient
  56. Konus-Wind detection of GRB 250217C (short)
  57. GRB 250219A: Swift/UVOT Upper Limits
  58. GRB 250219A: OHP/T193 optical upper limit
  59. GRB 250219A: NOT optical observations
  60. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  61. GRB 250219A: 1.6m Mephisto optical upper limits
  62. GRB 250219A: SVOM/VT optical counterpart
  63. GRB 250219A: Swift-XRT observations
  64. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  65. GRB 250219A: Swift ToO observations
  66. GRB 250219A: SVOM detection of a burst
  67. Konus-Wind detection of GRB 250215A / EP250215a
  68. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  69. GRB 250217C: Swift-XRT observations
  70. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  71. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  72. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  73. GRB 250217C: SVOM/GRM observation
  74. GRB 250217C: Tiled Swift observations
  75. GRB 250217C: Fermi GBM Observation
  76. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  77. IPN triangulation of GRB 250217C (short)
  78. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  79. SVOM/sb25021804: SVOM detection of a long X-ray transient
  80. GRB 250213A: Swift-XRT observations
  81. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  82. GRB 250216A: AstroSat CZTI detection
  83. GRB 250217C: AstroSat CZTI detection of a short burst
  84. Fermi GRB 250217C: Global MASTER-Net observations report
  85. GRB 250217C: Fermi GBM Final Real-time Localization
  86. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  87. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  88. Fermi GRB 250217A: Global MASTER-Net observations report
  89. GRANDMA/OPD observations of GRB250215A
  90. GRB 250217B: Fermi GBM Final Real-time Localization
  91. The EP-WXT trigger 01709131775 is likely a flaring star
  92. GRB 250217A: Fermi GBM Final Real-time Localization
  93. Fermi GRB 250216A: Global MASTER-Net observations report
  94. GRB 250215A / EP250215a: LCO detection of the afterglow
  95. GRB 250216A: Fermi GBM Final Real-time Localization
  96. EP250212a: FTW optical and NIR upper limits
  97. GRB 250215A: Swift/UVOT Upper Limits
  98. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  99. EP250215a / GRB 250215A : GTC redshift z = 4.61
  100. GRB 250215A: Fermi GBM Observation

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