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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"

39149 results found.

  1. EP250223a: CrAO ZTSH optical observation
  2. GRB 250225B: VLT optical and near-infrared candidate counterpart
  3. GRB 250225B: VLT/FORS2 candidate optical afterglow
  4. GRB 250225B: SVOM/GRM observation of a long burst
  5. GRB 250226A: GECAM-B detection
  6. GRB 250221A: EP-FXT detection of the X-ray afterglow
  7. GRB 250214A: SVOM/GRM observation
  8. EP250226a/GRB 250226A: GSP detects optical counterpart
  9. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  10. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  11. EP250226a / GRB 250226A: TRT optical counterpart observation
  12. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  13. EP250226a: Global MASTER-Net observations report
  14. Swift GRB 250225B: Global MASTER-Net observations report
  15. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  16. Fermi GRB 250226A: Global MASTER-Net observations report
  17. Fermi trigger No 762205158: Global MASTER-Net observations report
  18. GRB 250226A: Fermi GBM Final Real-time Localization
  19. EP250225a: Global MASTER-Net observations report
  20. EP250225a: GSP optical upper limit
  21. Fermi GRB 250225A: Global MASTER-Net observations report
  22. GRB 250225B: Swift detection of a burst
  23. EP250223a: GROWTH-India Telescope optical observations
  24. GRB 250221A: Swift-BAT refined analysis
  25. GRB 250223C: SVOM/GRM observation of a long burst
  26. GRB 250225A: Fermi GBM Final Real-time Localization
  27. GRB 250207a: ATCA Radio Upper Limits
  28. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  29. GRB 250119B: VZLUSAT-2 detection
  30. GRB 250223C: Fermi GBM Final Real-time Localization
  31. GRB 250202B: VZLUSAT-2 detection
  32. GRB 250219A: EP-FXT afterglow detection
  33. GRB 250222A: SVOM/GRM observation of a burst
  34. GRB 250210A: VZLUSAT-2 detection
  35. GRB 250206A: VZLUSAT-2 detection
  36. EP250223a: REM NIR upper limit
  37. EP250223a: TRT optical afterglow observation
  38. EP250223a: 1.6m Mephisto and 50cm array observations
  39. GRB 250221A: TNOT detection of the optical counterpart
  40. 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
  41. EP250223a: OASDG optical observations
  42. EP250223a: LCO detection of the afterglow
  43. GRB 250223B: Fermi GBM Final Localization
  44. EP250223a: Global MASTER-Net observations report
  45. GRB 250221A: VLA radio detection
  46. Fermi GRB 250223A: Global MASTER-Net observations report
  47. Fermi trigger No 762020305: Global MASTER-Net observations report
  48. GRB 250223A: Fermi GBM Final Real-time Localization
  49. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  50. GRB 250221A: continued Mondy optical observations, brightening afterglow
  51. GRB 250221A: Optical counterpart detection by LCO.
  52. GRB 250221A: Mondy optical observations
  53. Konus-Wind detection of GRB 250221A
  54. GRB 250221A: Assy optical observations
  55. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  56. GRB 250221A: VLT/X-shooter redshift z = 0.768
  57. GRB 250221A: GRANDMA/TAROT Detection
  58. Fermi trigger No 761805304: Global MASTER-Net observations report
  59. Fermi Gamma-ray Burst Monitor trigger 761867337/250221909 is not a GRB
  60. GRB 250221A: Swift-XRT refined Analysis
  61. GRB 250221A: NOT optical observations
  62. GRB 250221A: 1.6m Mephisto optical detection
  63. GRB 250221A: AKO Optical Upper Limit
  64. GRB 250221A: Swift/UVOT Detection
  65. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  66. GRB 250221A: REM optical/NIR afterglow detection
  67. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  68. GRB 250221A: Enhanced Swift-XRT position
  69. EP250220a: 1.6m Mephisto observations
  70. SVOM/sb25022102: SVOM detection of an X-ray transient
  71. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  72. GRB 250221A: Swift detection of a burst with an optical counterpart
  73. Swift GRB250221.15: Global MASTER-Net OT detection
  74. Swift GRB250221.15: Global MASTER-Net observations report
  75. Fermi Gamma-ray Burst Monitor trigger 761788229/250220993 is not a GRB
  76. GRB 250220B: Fermi GBM Final Real-time Localization
  77. Fermi Gamma-ray Burst Monitor trigger 761782146/250220923 is not a GRB
  78. GRB 250220A: Fermi GBM Final Real-time Localization
  79. EP250220a: Global MASTER-Net observations report
  80. Konus-Wind detection of GRB 250217C (short)
  81. GRB 250219A: Swift/UVOT Upper Limits
  82. GRB 250219A: OHP/T193 optical upper limit
  83. GRB 250219A: NOT optical observations
  84. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  85. GRB 250219A: 1.6m Mephisto optical upper limits
  86. GRB 250219A: SVOM/VT optical counterpart
  87. GRB 250219A: Swift-XRT observations
  88. GRB 250219A: Swift ToO observations
  89. GRB 250219A: SVOM detection of a burst
  90. Konus-Wind detection of GRB 250215A / EP250215a
  91. GRB 250217C: Swift-XRT 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. SVOM/sb25021804: SVOM detection of a long X-ray transient
  100. GRB 250213A: Swift-XRT observations

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