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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"

45423 results found.

  1. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  2. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  3. GRB 250119B: VZLUSAT-2 detection
  4. GRB 250223C: Fermi GBM Final Real-time Localization
  5. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  6. GRB 250202B: VZLUSAT-2 detection
  7. GRB 250219A: EP-FXT afterglow detection
  8. EP250223a: GOTO optical afterglow detections
  9. GRB 250222A: SVOM/GRM observation of a burst
  10. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  11. GRB 250210A: VZLUSAT-2 detection
  12. GRB 250206A: VZLUSAT-2 detection
  13. EP250223a: REM NIR upper limit
  14. EP250223a: TRT optical afterglow observation
  15. EP250223a: refined analysis of the EP-WXT and FXT observations
  16. EP250223a: 1.6m Mephisto and 50cm array observations
  17. GRB 250221A: TNOT detection of the optical counterpart
  18. EP250223a: SVOM/VT optical observation
  19. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  20. 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
  21. The EP-WXT trigger 01709131882 is likely a flaring star
  22. EP250223a: OASDG optical observations
  23. EP250223a: LCO detection of the afterglow
  24. EP250223a: early optical detection by BOOTES-4
  25. EP250223a: NOT redshift z = 2.756
  26. EP250223a: Swift/XRT localization
  27. EP250223a: NOT optical afterglow candidate
  28. GRB 250223B: Fermi GBM Final Localization
  29. EP250223a: Global MASTER-Net observations report
  30. GRB 250221A: VLA radio detection
  31. Fermi GRB 250223A: Global MASTER-Net observations report
  32. Fermi trigger No 762020305: Global MASTER-Net observations report
  33. GRB 250223A: Fermi GBM Final Real-time Localization
  34. EP250223a: Einstein Probe detection of an X-ray transient
  35. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  36. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  37. GRB 250221A: continued Mondy optical observations, brightening afterglow
  38. GRB 250221A: Optical counterpart detection by LCO.
  39. GRB 250221A: Mondy optical observations
  40. Konus-Wind detection of GRB 250221A
  41. GRB 250221A: Assy optical observations
  42. EP250220a: FTW optical and NIR observations and upper limits
  43. EP250220a: EP-FXT follow-up observations
  44. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  45. GRB 250221A: VLT/X-shooter redshift z = 0.768
  46. GRB 250221A: GRANDMA/TAROT Detection
  47. Fermi trigger No 761805304: Global MASTER-Net observations report
  48. Fermi Gamma-ray Burst Monitor trigger 761867337/250221909 is not a GRB
  49. GRB 250221A: Swift-XRT refined Analysis
  50. GRB 250221A: NOT optical observations
  51. GRB 250221A: 1.6m Mephisto optical detection
  52. LIGO/Virgo/KAGRA S250221gb: Retraction of GW compact binary merger candidate
  53. GRB 250221A: AKO Optical Upper Limit
  54. GRB 250221A: Swift/UVOT Detection
  55. EP250220a: Liverpool Telescope upper limits
  56. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  57. GRB 250221A: REM optical/NIR afterglow detection
  58. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  59. GRB 250221A: Enhanced Swift-XRT position
  60. LIGO/Virgo/KAGRA S250221eb: Retraction of GW compact binary merger candidate
  61. EP250220a: 1.6m Mephisto observations
  62. EP250220a: Liverpool Telescope optical upper limits
  63. EP250220a: Optical upper limit with Kinder observations
  64. SVOM trigger sb25022102 is not an astrophysical event
  65. SVOM/sb25022102: SVOM detection of an X-ray transient
  66. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  67. GRB 250221A: Swift detection of a burst with an optical counterpart
  68. Swift GRB250221.15: Global MASTER-Net OT detection
  69. Swift GRB250221.15: Global MASTER-Net observations report
  70. EP250220a: Xinglong optical upper limit
  71. Fermi Gamma-ray Burst Monitor trigger 761788229/250220993 is not a GRB
  72. GRB 250220B: Fermi GBM Final Real-time Localization
  73. Fermi Gamma-ray Burst Monitor trigger 761782146/250220923 is not a GRB
  74. GRB 250220A: Fermi GBM Final Real-time Localization
  75. EP250220a: Global MASTER-Net observations report
  76. EP250220a: EP-WXT detection of a fast X-ray transient
  77. Konus-Wind detection of GRB 250217C (short)
  78. GRB 250219A: Swift/UVOT Upper Limits
  79. GRB 250219A: OHP/T193 optical upper limit
  80. GRB 250219A: NOT optical observations
  81. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  82. GRB 250219A: 1.6m Mephisto optical upper limits
  83. GRB 250219A: SVOM/VT optical counterpart
  84. GRB 250219A: Swift-XRT observations
  85. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  86. GRB 250219A: Swift ToO observations
  87. GRB 250219A: SVOM detection of a burst
  88. Konus-Wind detection of GRB 250215A / EP250215a
  89. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  90. GRB 250217C: Swift-XRT observations
  91. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  92. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  93. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  94. GRB 250217C: SVOM/GRM observation
  95. GRB 250217C: Tiled Swift observations
  96. GRB 250217C: Fermi GBM Observation
  97. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  98. IPN triangulation of GRB 250217C (short)
  99. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  100. SVOM/sb25021804: SVOM detection of a long X-ray transient

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