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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"

43953 results found.

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