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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"

38258 results found.

  1. EP250226a/GRB 250226A: Kinder optical follow-up observations
  2. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  3. Fermi GRB 250226B: Global MASTER-Net observations report
  4. GRB 250226B: Fermi GBM Final Real-time Localization
  5. GRB 250225B: Fermi GBM Observation
  6. GRB 250221A: ATCA Detections and Upper Limits
  7. GRB 250225B: REM NIR upper limits
  8. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  9. Konus-Wind detection of GRB 250225B
  10. EP250223a: CrAO ZTSH optical observation
  11. GRB 250225B: VLT optical and near-infrared candidate counterpart
  12. GRB 250225B: VLT/FORS2 candidate optical afterglow
  13. GRB 250225B: SVOM/GRM observation of a long burst
  14. GRB 250226A: GECAM-B detection
  15. GRB 250221A: EP-FXT detection of the X-ray afterglow
  16. GRB 250214A: SVOM/GRM observation
  17. EP250226a/GRB 250226A: GSP detects optical counterpart
  18. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  19. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  20. EP250226a / GRB 250226A: TRT optical counterpart observation
  21. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  22. EP250226a: Global MASTER-Net observations report
  23. Swift GRB 250225B: Global MASTER-Net observations report
  24. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  25. Fermi GRB 250226A: Global MASTER-Net observations report
  26. Fermi trigger No 762205158: Global MASTER-Net observations report
  27. GRB 250226A: Fermi GBM Final Real-time Localization
  28. EP250225a: Global MASTER-Net observations report
  29. EP250225a: GSP optical upper limit
  30. Fermi GRB 250225A: Global MASTER-Net observations report
  31. GRB 250225B: Swift detection of a burst
  32. EP250223a: GROWTH-India Telescope optical observations
  33. GRB 250221A: Swift-BAT refined analysis
  34. GRB 250223C: SVOM/GRM observation of a long burst
  35. GRB 250225A: Fermi GBM Final Real-time Localization
  36. GRB 250207a: ATCA Radio Upper Limits
  37. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  38. GRB 250119B: VZLUSAT-2 detection
  39. GRB 250223C: Fermi GBM Final Real-time Localization
  40. GRB 250202B: VZLUSAT-2 detection
  41. GRB 250219A: EP-FXT afterglow detection
  42. GRB 250222A: SVOM/GRM observation of a burst
  43. GRB 250210A: VZLUSAT-2 detection
  44. GRB 250206A: VZLUSAT-2 detection
  45. EP250223a: REM NIR upper limit
  46. EP250223a: TRT optical afterglow observation
  47. EP250223a: 1.6m Mephisto and 50cm array observations
  48. GRB 250221A: TNOT detection of the optical counterpart
  49. 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
  50. EP250223a: OASDG optical observations
  51. EP250223a: LCO detection of the afterglow
  52. GRB 250223B: Fermi GBM Final Localization
  53. EP250223a: Global MASTER-Net observations report
  54. GRB 250221A: VLA radio detection
  55. Fermi GRB 250223A: Global MASTER-Net observations report
  56. Fermi trigger No 762020305: Global MASTER-Net observations report
  57. GRB 250223A: Fermi GBM Final Real-time Localization
  58. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  59. GRB 250221A: continued Mondy optical observations, brightening afterglow
  60. GRB 250221A: Optical counterpart detection by LCO.
  61. GRB 250221A: Mondy optical observations
  62. Konus-Wind detection of GRB 250221A
  63. GRB 250221A: Assy optical observations
  64. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  65. GRB 250221A: VLT/X-shooter redshift z = 0.768
  66. GRB 250221A: GRANDMA/TAROT Detection
  67. Fermi trigger No 761805304: Global MASTER-Net observations report
  68. Fermi Gamma-ray Burst Monitor trigger 761867337/250221909 is not a GRB
  69. GRB 250221A: Swift-XRT refined Analysis
  70. GRB 250221A: NOT optical observations
  71. GRB 250221A: 1.6m Mephisto optical detection
  72. GRB 250221A: AKO Optical Upper Limit
  73. GRB 250221A: Swift/UVOT Detection
  74. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  75. GRB 250221A: REM optical/NIR afterglow detection
  76. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  77. GRB 250221A: Enhanced Swift-XRT position
  78. EP250220a: 1.6m Mephisto observations
  79. SVOM/sb25022102: SVOM detection of an X-ray transient
  80. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  81. GRB 250221A: Swift detection of a burst with an optical counterpart
  82. Swift GRB250221.15: Global MASTER-Net OT detection
  83. Swift GRB250221.15: Global MASTER-Net observations report
  84. Fermi Gamma-ray Burst Monitor trigger 761788229/250220993 is not a GRB
  85. GRB 250220B: Fermi GBM Final Real-time Localization
  86. Fermi Gamma-ray Burst Monitor trigger 761782146/250220923 is not a GRB
  87. GRB 250220A: Fermi GBM Final Real-time Localization
  88. EP250220a: Global MASTER-Net observations report
  89. Konus-Wind detection of GRB 250217C (short)
  90. GRB 250219A: Swift/UVOT Upper Limits
  91. GRB 250219A: OHP/T193 optical upper limit
  92. GRB 250219A: NOT optical observations
  93. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  94. GRB 250219A: 1.6m Mephisto optical upper limits
  95. GRB 250219A: SVOM/VT optical counterpart
  96. GRB 250219A: Swift-XRT observations
  97. GRB 250219A: Swift ToO observations
  98. GRB 250219A: SVOM detection of a burst
  99. Konus-Wind detection of GRB 250215A / EP250215a
  100. GRB 250217C: Swift-XRT observations

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