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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"

36135 results found.

  1. GRB 250225B: Swift detection of a burst
  2. GRB 250221A: Swift-BAT refined analysis
  3. GRB 250223C: SVOM/GRM observation of a long burst
  4. GRB 250225A: Fermi GBM Final Real-time Localization
  5. GRB 250207a: ATCA Radio Upper Limits
  6. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  7. GRB 250119B: VZLUSAT-2 detection
  8. GRB 250223C: Fermi GBM Final Real-time Localization
  9. GRB 250202B: VZLUSAT-2 detection
  10. GRB 250219A: EP-FXT afterglow detection
  11. GRB 250222A: SVOM/GRM observation of a burst
  12. GRB 250210A: VZLUSAT-2 detection
  13. GRB 250206A: VZLUSAT-2 detection
  14. GRB 250221A: TNOT detection of the optical counterpart
  15. 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
  16. EP250223a: OASDG optical observations
  17. GRB 250223B: Fermi GBM Final Localization
  18. GRB 250221A: VLA radio detection
  19. Fermi GRB 250223A: Global MASTER-Net observations report
  20. GRB 250223A: Fermi GBM Final Real-time Localization
  21. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  22. GRB 250221A: continued Mondy optical observations, brightening afterglow
  23. GRB 250221A: Optical counterpart detection by LCO.
  24. GRB 250221A: Mondy optical observations
  25. Konus-Wind detection of GRB 250221A
  26. GRB 250221A: Assy optical observations
  27. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  28. GRB 250221A: VLT/X-shooter redshift z = 0.768
  29. GRB 250221A: GRANDMA/TAROT Detection
  30. Fermi Gamma-ray Burst Monitor trigger 761867337/250221909 is not a GRB
  31. GRB 250221A: Swift-XRT refined Analysis
  32. GRB 250221A: NOT optical observations
  33. GRB 250221A: 1.6m Mephisto optical detection
  34. GRB 250221A: AKO Optical Upper Limit
  35. GRB 250221A: Swift/UVOT Detection
  36. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  37. GRB 250221A: REM optical/NIR afterglow detection
  38. GRB 250221A: Enhanced Swift-XRT position
  39. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  40. GRB 250221A: Swift detection of a burst with an optical counterpart
  41. Fermi Gamma-ray Burst Monitor trigger 761788229/250220993 is not a GRB
  42. GRB 250220B: Fermi GBM Final Real-time Localization
  43. Fermi Gamma-ray Burst Monitor trigger 761782146/250220923 is not a GRB
  44. GRB 250220A: Fermi GBM Final Real-time Localization
  45. Konus-Wind detection of GRB 250217C (short)
  46. GRB 250219A: Swift/UVOT Upper Limits
  47. GRB 250219A: OHP/T193 optical upper limit
  48. GRB 250219A: NOT optical observations
  49. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  50. GRB 250219A: 1.6m Mephisto optical upper limits
  51. GRB 250219A: SVOM/VT optical counterpart
  52. GRB 250219A: Swift-XRT observations
  53. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  54. GRB 250219A: Swift ToO observations
  55. GRB 250219A: SVOM detection of a burst
  56. Konus-Wind detection of GRB 250215A / EP250215a
  57. GRB 250217C: Swift-XRT observations
  58. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  59. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  60. GRB 250217C: SVOM/GRM observation
  61. GRB 250217C: Tiled Swift observations
  62. GRB 250217C: Fermi GBM Observation
  63. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  64. IPN triangulation of GRB 250217C (short)
  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. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  72. Fermi GRB 250217A: Global MASTER-Net observations report
  73. GRANDMA/OPD observations of GRB250215A
  74. GRB 250217B: Fermi GBM Final Real-time Localization
  75. GRB 250217A: Fermi GBM Final Real-time Localization
  76. Fermi GRB 250216A: Global MASTER-Net observations report
  77. GRB 250215A / EP250215a: LCO detection of the afterglow
  78. GRB 250216A: Fermi GBM Final Real-time Localization
  79. GRB 250215A: Swift/UVOT Upper Limits
  80. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  81. EP250215a / GRB 250215A : GTC redshift z = 4.61
  82. GRB 250215A: Fermi GBM Observation
  83. EP250215a / GRB 250215A : NOT optical observations
  84. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  85. GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
  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/GRB 250215A: INTEGRAL SPI-ACS detection
  92. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  93. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  94. Fermi GRB 250215A: Global MASTER-Net observations report
  95. GRB 250215A: Fermi GBM Final Real-time Localization
  96. GRB 250213A：SVOM/VT optical candidate
  97. Fermi Gamma-ray Burst Monitor trigger 761206993/250214266 is not a GRB
  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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