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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

46004 results found.

  1. GRB 250221A: continued Mondy optical observations, brightening afterglow
  2. GRB 250221A: Optical counterpart detection by LCO.
  3. GRB 250221A: Mondy optical observations
  4. Konus-Wind detection of GRB 250221A
  5. GRB 250221A: Assy optical observations
  6. EP250220a: FTW optical and NIR observations and upper limits
  7. EP250220a: EP-FXT follow-up observations
  8. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  9. GRB 250221A: VLT/X-shooter redshift z = 0.768
  10. GRB 250221A: GRANDMA/TAROT Detection
  11. Fermi trigger No 761805304: Global MASTER-Net observations report
  12. Fermi Gamma-ray Burst Monitor trigger 761867337/250221909 is not a GRB
  13. GRB 250221A: Swift-XRT refined Analysis
  14. GRB 250221A: NOT optical observations
  15. GRB 250221A: 1.6m Mephisto optical detection
  16. LIGO/Virgo/KAGRA S250221gb: Retraction of GW compact binary merger candidate
  17. GRB 250221A: AKO Optical Upper Limit
  18. GRB 250221A: Swift/UVOT Detection
  19. EP250220a: Liverpool Telescope upper limits
  20. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  21. GRB 250221A: REM optical/NIR afterglow detection
  22. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  23. GRB 250221A: Enhanced Swift-XRT position
  24. LIGO/Virgo/KAGRA S250221eb: Retraction of GW compact binary merger candidate
  25. EP250220a: 1.6m Mephisto observations
  26. EP250220a: Liverpool Telescope optical upper limits
  27. EP250220a: Optical upper limit with Kinder observations
  28. SVOM trigger sb25022102 is not an astrophysical event
  29. SVOM/sb25022102: SVOM detection of an X-ray transient
  30. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  31. GRB 250221A: Swift detection of a burst with an optical counterpart
  32. Swift GRB250221.15: Global MASTER-Net OT detection
  33. Swift GRB250221.15: Global MASTER-Net observations report
  34. EP250220a: Xinglong optical upper limit
  35. Fermi Gamma-ray Burst Monitor trigger 761788229/250220993 is not a GRB
  36. GRB 250220B: Fermi GBM Final Real-time Localization
  37. Fermi Gamma-ray Burst Monitor trigger 761782146/250220923 is not a GRB
  38. GRB 250220A: Fermi GBM Final Real-time Localization
  39. EP250220a: Global MASTER-Net observations report
  40. EP250220a: EP-WXT detection of a fast X-ray transient
  41. Konus-Wind detection of GRB 250217C (short)
  42. GRB 250219A: Swift/UVOT Upper Limits
  43. GRB 250219A: OHP/T193 optical upper limit
  44. GRB 250219A: NOT optical observations
  45. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  46. GRB 250219A: 1.6m Mephisto optical upper limits
  47. GRB 250219A: SVOM/VT optical counterpart
  48. GRB 250219A: Swift-XRT observations
  49. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  50. GRB 250219A: Swift ToO observations
  51. GRB 250219A: SVOM detection of a burst
  52. Konus-Wind detection of GRB 250215A / EP250215a
  53. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  54. GRB 250217C: Swift-XRT observations
  55. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  56. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  57. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  58. GRB 250217C: SVOM/GRM observation
  59. GRB 250217C: Tiled Swift observations
  60. GRB 250217C: Fermi GBM Observation
  61. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  62. IPN triangulation of GRB 250217C (short)
  63. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  64. SVOM/sb25021804: SVOM detection of a long X-ray transient
  65. GRB 250213A: Swift-XRT observations
  66. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  67. GRB 250216A: AstroSat CZTI detection
  68. GRB 250217C: AstroSat CZTI detection of a short burst
  69. Fermi GRB 250217C: Global MASTER-Net observations report
  70. GRB 250217C: Fermi GBM Final Real-time Localization
  71. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  72. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  73. Fermi GRB 250217A: Global MASTER-Net observations report
  74. GRANDMA/OPD observations of GRB250215A
  75. GRB 250217B: Fermi GBM Final Real-time Localization
  76. The EP-WXT trigger 01709131775 is likely a flaring star
  77. GRB 250217A: Fermi GBM Final Real-time Localization
  78. Fermi GRB 250216A: Global MASTER-Net observations report
  79. GRB 250215A / EP250215a: LCO detection of the afterglow
  80. GRB 250216A: Fermi GBM Final Real-time Localization
  81. EP250212a: FTW optical and NIR upper limits
  82. GRB 250215A: Swift/UVOT Upper Limits
  83. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  84. EP250215a / GRB 250215A : GTC redshift z = 4.61
  85. GRB 250215A: Fermi GBM Observation
  86. EP250215a / GRB 250215A : NOT optical observations
  87. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  88. GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
  89. LIGO/Virgo/KAGRA S250206dm: MASTER LC AT2025bbo
  90. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  91. GRB 250215A: Swift-XRT refined Analysis
  92. GRB 250215A: SVOM/GRM observation
  93. EP250215a / GRB 250215A: AstroSat CZTI detection
  94. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  95. EP250215a: Global MASTER-Net observations report
  96. EP250215A/GRB 250215A: INTEGRAL SPI-ACS detection
  97. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  98. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  99. Fermi GRB 250215A: Global MASTER-Net observations report
  100. GRB 250215A: Fermi GBM Final Real-time Localization

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