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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"

38169 results found.

  1. GRB 250205A / EP250205A: further radio observations with the VLA
  2. GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
  3. EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
  4. GRB 250225B: INTEGRAL SPI-ACS detection
  5. EP250225a: NOT optical candidate counterpart
  6. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  7. EP250226a / GRB 250226A: SVOM/VT optical observations
  8. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  9. EP250225a: TRT optical upper limits
  10. EP250226a/GRB 250226A: 1.6m Mephisto observations
  11. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  12. EP250226a/GRB 250226A: Kinder optical follow-up observations
  13. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  14. Fermi GRB 250226B: Global MASTER-Net observations report
  15. GRB 250226B: Fermi GBM Final Real-time Localization
  16. GRB 250225B: Fermi GBM Observation
  17. GRB 250221A: ATCA Detections and Upper Limits
  18. GRB 250225B: REM NIR upper limits
  19. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  20. Konus-Wind detection of GRB 250225B
  21. EP250223a: CrAO ZTSH optical observation
  22. GRB 250225B: VLT optical and near-infrared candidate counterpart
  23. GRB 250225B: VLT/FORS2 candidate optical afterglow
  24. GRB 250225B: SVOM/GRM observation of a long burst
  25. GRB 250226A: GECAM-B detection
  26. GRB 250221A: EP-FXT detection of the X-ray afterglow
  27. GRB 250214A: SVOM/GRM observation
  28. EP250226a/GRB 250226A: GSP detects optical counterpart
  29. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  30. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  31. EP250226a / GRB 250226A: TRT optical counterpart observation
  32. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  33. EP250226a: Global MASTER-Net observations report
  34. Swift GRB 250225B: Global MASTER-Net observations report
  35. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  36. Fermi GRB 250226A: Global MASTER-Net observations report
  37. Fermi trigger No 762205158: Global MASTER-Net observations report
  38. GRB 250226A: Fermi GBM Final Real-time Localization
  39. EP250225a: Global MASTER-Net observations report
  40. EP250225a: GSP optical upper limit
  41. Fermi GRB 250225A: Global MASTER-Net observations report
  42. GRB 250225B: Swift detection of a burst
  43. EP250223a: GROWTH-India Telescope optical observations
  44. GRB 250221A: Swift-BAT refined analysis
  45. GRB 250223C: SVOM/GRM observation of a long burst
  46. GRB 250225A: Fermi GBM Final Real-time Localization
  47. GRB 250207a: ATCA Radio Upper Limits
  48. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  49. GRB 250119B: VZLUSAT-2 detection
  50. GRB 250223C: Fermi GBM Final Real-time Localization
  51. GRB 250202B: VZLUSAT-2 detection
  52. GRB 250219A: EP-FXT afterglow detection
  53. GRB 250222A: SVOM/GRM observation of a burst
  54. GRB 250210A: VZLUSAT-2 detection
  55. GRB 250206A: VZLUSAT-2 detection
  56. EP250223a: REM NIR upper limit
  57. EP250223a: TRT optical afterglow observation
  58. EP250223a: 1.6m Mephisto and 50cm array observations
  59. GRB 250221A: TNOT detection of the optical counterpart
  60. 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
  61. EP250223a: OASDG optical observations
  62. EP250223a: LCO detection of the afterglow
  63. GRB 250223B: Fermi GBM Final Localization
  64. EP250223a: Global MASTER-Net observations report
  65. GRB 250221A: VLA radio detection
  66. Fermi GRB 250223A: Global MASTER-Net observations report
  67. Fermi trigger No 762020305: Global MASTER-Net observations report
  68. GRB 250223A: Fermi GBM Final Real-time Localization
  69. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  70. GRB 250221A: continued Mondy optical observations, brightening afterglow
  71. GRB 250221A: Optical counterpart detection by LCO.
  72. GRB 250221A: Mondy optical observations
  73. Konus-Wind detection of GRB 250221A
  74. GRB 250221A: Assy optical observations
  75. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  76. GRB 250221A: VLT/X-shooter redshift z = 0.768
  77. GRB 250221A: GRANDMA/TAROT Detection
  78. Fermi trigger No 761805304: Global MASTER-Net observations report
  79. Fermi Gamma-ray Burst Monitor trigger 761867337/250221909 is not a GRB
  80. GRB 250221A: Swift-XRT refined Analysis
  81. GRB 250221A: NOT optical observations
  82. GRB 250221A: 1.6m Mephisto optical detection
  83. GRB 250221A: AKO Optical Upper Limit
  84. GRB 250221A: Swift/UVOT Detection
  85. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  86. GRB 250221A: REM optical/NIR afterglow detection
  87. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  88. GRB 250221A: Enhanced Swift-XRT position
  89. EP250220a: 1.6m Mephisto observations
  90. SVOM/sb25022102: SVOM detection of an X-ray transient
  91. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  92. GRB 250221A: Swift detection of a burst with an optical counterpart
  93. Swift GRB250221.15: Global MASTER-Net OT detection
  94. Swift GRB250221.15: Global MASTER-Net observations report
  95. Fermi Gamma-ray Burst Monitor trigger 761788229/250220993 is not a GRB
  96. GRB 250220B: Fermi GBM Final Real-time Localization
  97. Fermi Gamma-ray Burst Monitor trigger 761782146/250220923 is not a GRB
  98. GRB 250220A: Fermi GBM Final Real-time Localization
  99. EP250220a: Global MASTER-Net observations report
  100. Konus-Wind detection of GRB 250217C (short)

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