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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"

44404 results found.

  1. 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
  2. The EP-WXT trigger 01709131882 is likely a flaring star
  3. EP250223a: OASDG optical observations
  4. EP250223a: LCO detection of the afterglow
  5. EP250223a: early optical detection by BOOTES-4
  6. EP250223a: NOT redshift z = 2.756
  7. EP250223a: Swift/XRT localization
  8. EP250223a: NOT optical afterglow candidate
  9. GRB 250223B: Fermi GBM Final Localization
  10. EP250223a: Global MASTER-Net observations report
  11. GRB 250221A: VLA radio detection
  12. Fermi GRB 250223A: Global MASTER-Net observations report
  13. Fermi trigger No 762020305: Global MASTER-Net observations report
  14. GRB 250223A: Fermi GBM Final Real-time Localization
  15. EP250223a: Einstein Probe detection of an X-ray transient
  16. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  17. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  18. GRB 250221A: continued Mondy optical observations, brightening afterglow
  19. GRB 250221A: Optical counterpart detection by LCO.
  20. GRB 250221A: Mondy optical observations
  21. Konus-Wind detection of GRB 250221A
  22. GRB 250221A: Assy optical observations
  23. EP250220a: FTW optical and NIR observations and upper limits
  24. EP250220a: EP-FXT follow-up observations
  25. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  26. GRB 250221A: VLT/X-shooter redshift z = 0.768
  27. GRB 250221A: GRANDMA/TAROT Detection
  28. Fermi trigger No 761805304: Global MASTER-Net observations report
  29. Fermi Gamma-ray Burst Monitor trigger 761867337/250221909 is not a GRB
  30. GRB 250221A: Swift-XRT refined Analysis
  31. GRB 250221A: NOT optical observations
  32. GRB 250221A: 1.6m Mephisto optical detection
  33. LIGO/Virgo/KAGRA S250221gb: Retraction of GW compact binary merger candidate
  34. GRB 250221A: AKO Optical Upper Limit
  35. GRB 250221A: Swift/UVOT Detection
  36. EP250220a: Liverpool Telescope upper limits
  37. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  38. GRB 250221A: REM optical/NIR afterglow detection
  39. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  40. GRB 250221A: Enhanced Swift-XRT position
  41. LIGO/Virgo/KAGRA S250221eb: Retraction of GW compact binary merger candidate
  42. EP250220a: 1.6m Mephisto observations
  43. EP250220a: Liverpool Telescope optical upper limits
  44. EP250220a: Optical upper limit with Kinder observations
  45. SVOM trigger sb25022102 is not an astrophysical event
  46. SVOM/sb25022102: SVOM detection of an X-ray transient
  47. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  48. GRB 250221A: Swift detection of a burst with an optical counterpart
  49. Swift GRB250221.15: Global MASTER-Net OT detection
  50. Swift GRB250221.15: Global MASTER-Net observations report
  51. EP250220a: Xinglong optical upper limit
  52. Fermi Gamma-ray Burst Monitor trigger 761788229/250220993 is not a GRB
  53. GRB 250220B: Fermi GBM Final Real-time Localization
  54. Fermi Gamma-ray Burst Monitor trigger 761782146/250220923 is not a GRB
  55. GRB 250220A: Fermi GBM Final Real-time Localization
  56. EP250220a: Global MASTER-Net observations report
  57. EP250220a: EP-WXT detection of a fast X-ray transient
  58. Konus-Wind detection of GRB 250217C (short)
  59. GRB 250219A: Swift/UVOT Upper Limits
  60. GRB 250219A: OHP/T193 optical upper limit
  61. GRB 250219A: NOT optical observations
  62. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  63. GRB 250219A: 1.6m Mephisto optical upper limits
  64. GRB 250219A: SVOM/VT optical counterpart
  65. GRB 250219A: Swift-XRT observations
  66. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  67. GRB 250219A: Swift ToO observations
  68. GRB 250219A: SVOM detection of a burst
  69. Konus-Wind detection of GRB 250215A / EP250215a
  70. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  71. GRB 250217C: Swift-XRT observations
  72. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  73. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  74. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  75. GRB 250217C: SVOM/GRM observation
  76. GRB 250217C: Tiled Swift observations
  77. GRB 250217C: Fermi GBM Observation
  78. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  79. IPN triangulation of GRB 250217C (short)
  80. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  81. SVOM/sb25021804: SVOM detection of a long X-ray transient
  82. GRB 250213A: Swift-XRT observations
  83. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  84. GRB 250216A: AstroSat CZTI detection
  85. GRB 250217C: AstroSat CZTI detection of a short burst
  86. Fermi GRB 250217C: Global MASTER-Net observations report
  87. GRB 250217C: Fermi GBM Final Real-time Localization
  88. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  89. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  90. Fermi GRB 250217A: Global MASTER-Net observations report
  91. GRANDMA/OPD observations of GRB250215A
  92. GRB 250217B: Fermi GBM Final Real-time Localization
  93. The EP-WXT trigger 01709131775 is likely a flaring star
  94. GRB 250217A: Fermi GBM Final Real-time Localization
  95. Fermi GRB 250216A: Global MASTER-Net observations report
  96. GRB 250215A / EP250215a: LCO detection of the afterglow
  97. GRB 250216A: Fermi GBM Final Real-time Localization
  98. EP250212a: FTW optical and NIR upper limits
  99. GRB 250215A: Swift/UVOT Upper Limits
  100. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow

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