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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"

28079 results found.

  1. GRB 250221A: Optical counterpart detection by LCO.
  2. GRB 250221A: Mondy optical observations
  3. Konus-Wind detection of GRB 250221A
  4. GRB 250221A: Assy optical observations
  5. EP250220a: EP-FXT follow-up observations
  6. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  7. GRB 250221A: VLT/X-shooter redshift z = 0.768
  8. GRB 250221A: GRANDMA/TAROT Detection
  9. GRB 250221A: Swift-XRT refined Analysis
  10. GRB 250221A: NOT optical observations
  11. GRB 250221A: 1.6m Mephisto optical detection
  12. GRB 250221A: AKO Optical Upper Limit
  13. GRB 250221A: Swift/UVOT Detection
  14. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  15. GRB 250221A: REM optical/NIR afterglow detection
  16. GRB 250221A: Enhanced Swift-XRT position
  17. EP250220a: Liverpool Telescope optical upper limits
  18. EP250220a: Optical upper limit with Kinder observations
  19. SVOM trigger sb25022102 is not an astrophysical event
  20. SVOM/sb25022102: SVOM detection of an X-ray transient
  21. GRB 250221A: Swift detection of a burst with an optical counterpart
  22. Swift GRB250221.15: Global MASTER-Net OT detection
  23. EP250220a: Xinglong optical upper limit
  24. GRB 250220B: Fermi GBM Final Real-time Localization
  25. GRB 250220A: Fermi GBM Final Real-time Localization
  26. EP250220a: EP-WXT detection of a fast X-ray transient
  27. Konus-Wind detection of GRB 250217C (short)
  28. GRB 250219A: Swift/UVOT Upper Limits
  29. GRB 250219A: OHP/T193 optical upper limit
  30. GRB 250219A: NOT optical observations
  31. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  32. GRB 250219A: 1.6m Mephisto optical upper limits
  33. GRB 250219A: SVOM/VT optical counterpart
  34. GRB 250219A: Swift-XRT observations
  35. GRB 250219A: Swift ToO observations
  36. GRB 250219A: SVOM detection of a burst
  37. Konus-Wind detection of GRB 250215A / EP250215a
  38. GRB 250217C: Swift-XRT observations
  39. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  40. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  41. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  42. GRB 250217C: Tiled Swift observations
  43. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  44. IPN triangulation of GRB 250217C (short)
  45. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  46. SVOM/sb25021804: SVOM detection of a long X-ray transient
  47. GRB 250213A: Swift-XRT observations
  48. GRB 250216A: AstroSat CZTI detection
  49. GRB 250217C: AstroSat CZTI detection of a short burst
  50. GRB 250217C: Fermi GBM Final Real-time Localization
  51. GRANDMA/OPD observations of GRB250215A
  52. GRB 250217B: Fermi GBM Final Real-time Localization
  53. GRB 250217A: Fermi GBM Final Real-time Localization
  54. GRB 250215A / EP250215a: LCO detection of the afterglow
  55. GRB 250216A: Fermi GBM Final Real-time Localization
  56. GRB 250215A: Swift/UVOT Upper Limits
  57. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  58. EP250215a / GRB 250215A : GTC redshift z = 4.61
  59. GRB 250215A: Fermi GBM Observation
  60. EP250215a / GRB 250215A : NOT optical observations
  61. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  62. GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
  63. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  64. GRB 250215A: Swift-XRT refined Analysis
  65. EP250215a / GRB 250215A: AstroSat CZTI detection
  66. EP250215A/GRB 250215A: INTEGRAL SPI-ACS detection
  67. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  68. GRB 250215A: Fermi GBM Final Real-time Localization
  69. EP250207b: Xinglong optical upper limit
  70. GRB 250213A: Swift ToO observations
  71. GRB 250214A: Fermi GBM Final Real-time Localization
  72. EP250212a: Xinglong optical upper limit
  73. GRB 250213A: SVOM detection of a burst
  74. GRB 250205A: VIRT Optical Upper Limit
  75. GRB 250205A: Leavitt Observatory optical upper limit
  76. GRB 250210A: GRBAlpha detection
  77. EP250207B: Chandra localization of the X-ray counterpart
  78. LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
  79. EP250212a: Liverpool Telescope optical upper limits
  80. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  81. GRB 250211A: Swift ToO observations
  82. GRB 250212A: Fermi GBM Final Real-time Localization
  83. GRB 250205A / EP250205A: radio detection with the VLA
  84. IceCube-250207A: One candidate from the Zwicky Transient Facility
  85. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  86. Konus-Wind detection of GRB 250207A
  87. Konus-Wind detection of GRB 250206A
  88. EP250207b: Liverpool Telescope possible optical counterpart
  89. Gemini-South spectroscopic redshift of EP250207b host galaxy candidate (z=0.082)
  90. GRB 250207A: Skynet optical afterglow observations
  91. LIGO/Virgo/KAGRA S250206dm: Gemini-North spectroscopic observation of AT2025bbo and its host galaxy
  92. GRB 241128A: VIRT Optical Upper Limit
  93. GRB 250210A: INTEGRAL SPI-ACS detection
  94. GRB 250210A: AstroSat CZTI detection
  95. EP250207b: a new X-ray transient detected by Einstein Probe
  96. LIGO/Virgo/KAGRA S250206dm: MASTER detection AT2025bbo
  97. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  98. GRB 250210A: Fermi GBM Final Real-time Localization
  99. LIGO/Virgo/KAGRA S250206dm: Upper limits from GECAM Observations
  100. GRB 250204B: GRBAlpha detection

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