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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"

45797 results found.

  1. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  2. GRB 250221A: VLT/X-shooter redshift z = 0.768
  3. GRB 250221A: GRANDMA/TAROT Detection
  4. Fermi trigger No 761805304: Global MASTER-Net observations report
  5. Fermi Gamma-ray Burst Monitor trigger 761867337/250221909 is not a GRB
  6. GRB 250221A: Swift-XRT refined Analysis
  7. GRB 250221A: NOT optical observations
  8. GRB 250221A: 1.6m Mephisto optical detection
  9. LIGO/Virgo/KAGRA S250221gb: Retraction of GW compact binary merger candidate
  10. GRB 250221A: AKO Optical Upper Limit
  11. GRB 250221A: Swift/UVOT Detection
  12. EP250220a: Liverpool Telescope upper limits
  13. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  14. GRB 250221A: REM optical/NIR afterglow detection
  15. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  16. GRB 250221A: Enhanced Swift-XRT position
  17. LIGO/Virgo/KAGRA S250221eb: Retraction of GW compact binary merger candidate
  18. EP250220a: 1.6m Mephisto observations
  19. EP250220a: Liverpool Telescope optical upper limits
  20. EP250220a: Optical upper limit with Kinder observations
  21. SVOM trigger sb25022102 is not an astrophysical event
  22. SVOM/sb25022102: SVOM detection of an X-ray transient
  23. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  24. GRB 250221A: Swift detection of a burst with an optical counterpart
  25. Swift GRB250221.15: Global MASTER-Net OT detection
  26. Swift GRB250221.15: Global MASTER-Net observations report
  27. EP250220a: Xinglong optical upper limit
  28. Fermi Gamma-ray Burst Monitor trigger 761788229/250220993 is not a GRB
  29. GRB 250220B: Fermi GBM Final Real-time Localization
  30. Fermi Gamma-ray Burst Monitor trigger 761782146/250220923 is not a GRB
  31. GRB 250220A: Fermi GBM Final Real-time Localization
  32. EP250220a: Global MASTER-Net observations report
  33. EP250220a: EP-WXT detection of a fast X-ray transient
  34. Konus-Wind detection of GRB 250217C (short)
  35. GRB 250219A: Swift/UVOT Upper Limits
  36. GRB 250219A: OHP/T193 optical upper limit
  37. GRB 250219A: NOT optical observations
  38. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  39. GRB 250219A: 1.6m Mephisto optical upper limits
  40. GRB 250219A: SVOM/VT optical counterpart
  41. GRB 250219A: Swift-XRT observations
  42. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  43. GRB 250219A: Swift ToO observations
  44. GRB 250219A: SVOM detection of a burst
  45. Konus-Wind detection of GRB 250215A / EP250215a
  46. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  47. GRB 250217C: Swift-XRT observations
  48. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  49. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  50. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  51. GRB 250217C: SVOM/GRM observation
  52. GRB 250217C: Tiled Swift observations
  53. GRB 250217C: Fermi GBM Observation
  54. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  55. IPN triangulation of GRB 250217C (short)
  56. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  57. SVOM/sb25021804: SVOM detection of a long X-ray transient
  58. GRB 250213A: Swift-XRT observations
  59. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  60. GRB 250216A: AstroSat CZTI detection
  61. GRB 250217C: AstroSat CZTI detection of a short burst
  62. Fermi GRB 250217C: Global MASTER-Net observations report
  63. GRB 250217C: Fermi GBM Final Real-time Localization
  64. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  65. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  66. Fermi GRB 250217A: Global MASTER-Net observations report
  67. GRANDMA/OPD observations of GRB250215A
  68. GRB 250217B: Fermi GBM Final Real-time Localization
  69. The EP-WXT trigger 01709131775 is likely a flaring star
  70. GRB 250217A: Fermi GBM Final Real-time Localization
  71. Fermi GRB 250216A: Global MASTER-Net observations report
  72. GRB 250215A / EP250215a: LCO detection of the afterglow
  73. GRB 250216A: Fermi GBM Final Real-time Localization
  74. EP250212a: FTW optical and NIR upper limits
  75. GRB 250215A: Swift/UVOT Upper Limits
  76. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  77. EP250215a / GRB 250215A : GTC redshift z = 4.61
  78. GRB 250215A: Fermi GBM Observation
  79. EP250215a / GRB 250215A : NOT optical observations
  80. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  81. GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
  82. LIGO/Virgo/KAGRA S250206dm: MASTER LC AT2025bbo
  83. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  84. GRB 250215A: Swift-XRT refined Analysis
  85. GRB 250215A: SVOM/GRM observation
  86. EP250215a / GRB 250215A: AstroSat CZTI detection
  87. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  88. EP250215a: Global MASTER-Net observations report
  89. EP250215A/GRB 250215A: INTEGRAL SPI-ACS detection
  90. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  91. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  92. Fermi GRB 250215A: Global MASTER-Net observations report
  93. GRB 250215A: Fermi GBM Final Real-time Localization
  94. Fermi trigger No 761206993: Global MASTER-Net observations report
  95. GRB 250213A：SVOM/VT optical candidate
  96. Fermi Gamma-ray Burst Monitor trigger 761206993/250214266 is not a GRB
  97. EP250207b: Xinglong optical upper limit
  98. Fermi GRB 250214A: Global MASTER-Net observations report
  99. GRB 250213A: Swift ToO observations
  100. GRB 250214A: Fermi GBM Final Real-time Localization

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