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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"

38216 results found.

  1. GRB 250210A: VZLUSAT-2 detection
  2. GRB 250206A: VZLUSAT-2 detection
  3. EP250223a: REM NIR upper limit
  4. EP250223a: TRT optical afterglow observation
  5. EP250223a: 1.6m Mephisto and 50cm array observations
  6. GRB 250221A: TNOT detection of the optical counterpart
  7. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO trigger with ID 762004910: Identification of a GW compact binary merger candidate possibly associated with a sub-threshold Swift/BAT-GUANO trigger
  8. EP250223a: OASDG optical observations
  9. EP250223a: LCO detection of the afterglow
  10. GRB 250223B: Fermi GBM Final Localization
  11. EP250223a: Global MASTER-Net observations report
  12. GRB 250221A: VLA radio detection
  13. Fermi GRB 250223A: Global MASTER-Net observations report
  14. Fermi trigger No 762020305: Global MASTER-Net observations report
  15. GRB 250223A: Fermi GBM Final Real-time Localization
  16. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  17. GRB 250221A: continued Mondy optical observations, brightening afterglow
  18. GRB 250221A: Optical counterpart detection by LCO.
  19. GRB 250221A: Mondy optical observations
  20. Konus-Wind detection of GRB 250221A
  21. GRB 250221A: Assy optical observations
  22. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  23. GRB 250221A: VLT/X-shooter redshift z = 0.768
  24. GRB 250221A: GRANDMA/TAROT Detection
  25. Fermi trigger No 761805304: Global MASTER-Net observations report
  26. Fermi Gamma-ray Burst Monitor trigger 761867337/250221909 is not a GRB
  27. GRB 250221A: Swift-XRT refined Analysis
  28. GRB 250221A: NOT optical observations
  29. GRB 250221A: 1.6m Mephisto optical detection
  30. GRB 250221A: AKO Optical Upper Limit
  31. GRB 250221A: Swift/UVOT Detection
  32. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  33. GRB 250221A: REM optical/NIR afterglow detection
  34. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  35. GRB 250221A: Enhanced Swift-XRT position
  36. EP250220a: 1.6m Mephisto observations
  37. SVOM/sb25022102: SVOM detection of an X-ray transient
  38. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  39. GRB 250221A: Swift detection of a burst with an optical counterpart
  40. Swift GRB250221.15: Global MASTER-Net OT detection
  41. Swift GRB250221.15: Global MASTER-Net observations report
  42. Fermi Gamma-ray Burst Monitor trigger 761788229/250220993 is not a GRB
  43. GRB 250220B: Fermi GBM Final Real-time Localization
  44. Fermi Gamma-ray Burst Monitor trigger 761782146/250220923 is not a GRB
  45. GRB 250220A: Fermi GBM Final Real-time Localization
  46. EP250220a: Global MASTER-Net observations report
  47. Konus-Wind detection of GRB 250217C (short)
  48. GRB 250219A: Swift/UVOT Upper Limits
  49. GRB 250219A: OHP/T193 optical upper limit
  50. GRB 250219A: NOT optical observations
  51. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  52. GRB 250219A: 1.6m Mephisto optical upper limits
  53. GRB 250219A: SVOM/VT optical counterpart
  54. GRB 250219A: Swift-XRT observations
  55. GRB 250219A: Swift ToO observations
  56. GRB 250219A: SVOM detection of a burst
  57. Konus-Wind detection of GRB 250215A / EP250215a
  58. GRB 250217C: Swift-XRT observations
  59. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  60. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  61. GRB 250217C: SVOM/GRM observation
  62. GRB 250217C: Tiled Swift observations
  63. GRB 250217C: Fermi GBM Observation
  64. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  65. IPN triangulation of GRB 250217C (short)
  66. SVOM/sb25021804: SVOM detection of a long X-ray transient
  67. GRB 250213A: Swift-XRT observations
  68. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  69. GRB 250216A: AstroSat CZTI detection
  70. GRB 250217C: AstroSat CZTI detection of a short burst
  71. Fermi GRB 250217C: Global MASTER-Net observations report
  72. GRB 250217C: Fermi GBM Final Real-time Localization
  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. 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. GRB 250215A: Swift/UVOT Upper Limits
  82. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  83. EP250215a / GRB 250215A : GTC redshift z = 4.61
  84. GRB 250215A: Fermi GBM Observation
  85. EP250215a / GRB 250215A : NOT optical observations
  86. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  87. GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
  88. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  89. GRB 250215A: Swift-XRT refined Analysis
  90. GRB 250215A: SVOM/GRM observation
  91. EP250215a / GRB 250215A: AstroSat CZTI detection
  92. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  93. EP250215a: Global MASTER-Net observations report
  94. EP250215A/GRB 250215A: INTEGRAL SPI-ACS detection
  95. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  96. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  97. Fermi GRB 250215A: Global MASTER-Net observations report
  98. GRB 250215A: Fermi GBM Final Real-time Localization
  99. Fermi trigger No 761206993: Global MASTER-Net observations report
  100. GRB 250213A：SVOM/VT optical candidate

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