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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"
  1. GRB 250221A: Assy optical observations
  2. EP250220a: FTW optical and NIR observations and upper limits
  3. EP250220a: EP-FXT follow-up observations
  4. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  5. GRB 250221A: VLT/X-shooter redshift z = 0.768
  6. GRB 250221A: GRANDMA/TAROT Detection
  7. Fermi trigger No 761805304: Global MASTER-Net observations report
  8. Fermi Gamma-ray Burst Monitor trigger 761867337/250221909 is not a GRB
  9. GRB 250221A: Swift-XRT refined Analysis
  10. GRB 250221A: NOT optical observations
  11. GRB 250221A: 1.6m Mephisto optical detection
  12. LIGO/Virgo/KAGRA S250221gb: Retraction of GW compact binary merger candidate
  13. GRB 250221A: AKO Optical Upper Limit
  14. GRB 250221A: Swift/UVOT Detection
  15. EP250220a: Liverpool Telescope upper limits
  16. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  17. GRB 250221A: REM optical/NIR afterglow detection
  18. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  19. GRB 250221A: Enhanced Swift-XRT position
  20. LIGO/Virgo/KAGRA S250221eb: Retraction of GW compact binary merger candidate
  21. EP250220a: 1.6m Mephisto observations
  22. EP250220a: Liverpool Telescope optical upper limits
  23. EP250220a: Optical upper limit with Kinder observations
  24. SVOM trigger sb25022102 is not an astrophysical event
  25. SVOM/sb25022102: SVOM detection of an X-ray transient
  26. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  27. GRB 250221A: Swift detection of a burst with an optical counterpart
  28. Swift GRB250221.15: Global MASTER-Net OT detection
  29. Swift GRB250221.15: Global MASTER-Net observations report
  30. EP250220a: Xinglong optical upper limit
  31. Fermi Gamma-ray Burst Monitor trigger 761788229/250220993 is not a GRB
  32. GRB 250220B: Fermi GBM Final Real-time Localization
  33. Fermi Gamma-ray Burst Monitor trigger 761782146/250220923 is not a GRB
  34. GRB 250220A: Fermi GBM Final Real-time Localization
  35. EP250220a: Global MASTER-Net observations report
  36. EP250220a: EP-WXT detection of a fast X-ray transient
  37. Konus-Wind detection of GRB 250217C (short)
  38. GRB 250219A: Swift/UVOT Upper Limits
  39. GRB 250219A: OHP/T193 optical upper limit
  40. GRB 250219A: NOT optical observations
  41. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  42. GRB 250219A: 1.6m Mephisto optical upper limits
  43. GRB 250219A: SVOM/VT optical counterpart
  44. GRB 250219A: Swift-XRT observations
  45. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  46. GRB 250219A: Swift ToO observations
  47. GRB 250219A: SVOM detection of a burst
  48. Konus-Wind detection of GRB 250215A / EP250215a
  49. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  50. GRB 250217C: Swift-XRT observations
  51. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  52. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  53. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  54. GRB 250217C: SVOM/GRM observation
  55. GRB 250217C: Tiled Swift observations
  56. GRB 250217C: Fermi GBM Observation
  57. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  58. IPN triangulation of GRB 250217C (short)
  59. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  60. SVOM/sb25021804: SVOM detection of a long X-ray transient
  61. GRB 250213A: Swift-XRT observations
  62. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  63. GRB 250216A: AstroSat CZTI detection
  64. GRB 250217C: AstroSat CZTI detection of a short burst
  65. Fermi GRB 250217C: Global MASTER-Net observations report
  66. GRB 250217C: Fermi GBM Final Real-time Localization
  67. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  68. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  69. Fermi GRB 250217A: Global MASTER-Net observations report
  70. GRANDMA/OPD observations of GRB250215A
  71. GRB 250217B: Fermi GBM Final Real-time Localization
  72. The EP-WXT trigger 01709131775 is likely a flaring star
  73. GRB 250217A: Fermi GBM Final Real-time Localization
  74. Fermi GRB 250216A: Global MASTER-Net observations report
  75. GRB 250215A / EP250215a: LCO detection of the afterglow
  76. GRB 250216A: Fermi GBM Final Real-time Localization
  77. EP250212a: FTW optical and NIR upper limits
  78. GRB 250215A: Swift/UVOT Upper Limits
  79. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  80. EP250215a / GRB 250215A : GTC redshift z = 4.61
  81. GRB 250215A: Fermi GBM Observation
  82. EP250215a / GRB 250215A : NOT optical observations
  83. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  84. GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
  85. LIGO/Virgo/KAGRA S250206dm: MASTER LC AT2025bbo
  86. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  87. GRB 250215A: Swift-XRT refined Analysis
  88. GRB 250215A: SVOM/GRM observation
  89. EP250215a / GRB 250215A: AstroSat CZTI detection
  90. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  91. EP250215a: Global MASTER-Net observations report
  92. EP250215A/GRB 250215A: INTEGRAL SPI-ACS detection
  93. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  94. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  95. Fermi GRB 250215A: Global MASTER-Net observations report
  96. GRB 250215A: Fermi GBM Final Real-time Localization
  97. Fermi trigger No 761206993: Global MASTER-Net observations report
  98. GRB 250213A：SVOM/VT optical candidate
  99. Fermi Gamma-ray Burst Monitor trigger 761206993/250214266 is not a GRB
  100. EP250207b: Xinglong optical upper limit

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