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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"

36140 results found.

  1. Swift GRB 250225B: Global MASTER-Net observations report
  2. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  3. Fermi GRB 250226A: Global MASTER-Net observations report
  4. GRB 250226A: Fermi GBM Final Real-time Localization
  5. Fermi GRB 250225A: Global MASTER-Net observations report
  6. GRB 250225B: Swift detection of a burst
  7. GRB 250221A: Swift-BAT refined analysis
  8. GRB 250223C: SVOM/GRM observation of a long burst
  9. GRB 250225A: Fermi GBM Final Real-time Localization
  10. GRB 250207a: ATCA Radio Upper Limits
  11. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  12. GRB 250119B: VZLUSAT-2 detection
  13. GRB 250223C: Fermi GBM Final Real-time Localization
  14. GRB 250202B: VZLUSAT-2 detection
  15. GRB 250219A: EP-FXT afterglow detection
  16. GRB 250222A: SVOM/GRM observation of a burst
  17. GRB 250210A: VZLUSAT-2 detection
  18. GRB 250206A: VZLUSAT-2 detection
  19. GRB 250221A: TNOT detection of the optical counterpart
  20. 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
  21. EP250223a: OASDG optical observations
  22. GRB 250223B: Fermi GBM Final Localization
  23. GRB 250221A: VLA radio detection
  24. Fermi GRB 250223A: Global MASTER-Net observations report
  25. GRB 250223A: Fermi GBM Final Real-time Localization
  26. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  27. GRB 250221A: continued Mondy optical observations, brightening afterglow
  28. GRB 250221A: Optical counterpart detection by LCO.
  29. GRB 250221A: Mondy optical observations
  30. Konus-Wind detection of GRB 250221A
  31. GRB 250221A: Assy optical observations
  32. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  33. GRB 250221A: VLT/X-shooter redshift z = 0.768
  34. GRB 250221A: GRANDMA/TAROT Detection
  35. Fermi Gamma-ray Burst Monitor trigger 761867337/250221909 is not a GRB
  36. GRB 250221A: Swift-XRT refined Analysis
  37. GRB 250221A: NOT optical observations
  38. GRB 250221A: 1.6m Mephisto optical detection
  39. GRB 250221A: AKO Optical Upper Limit
  40. GRB 250221A: Swift/UVOT Detection
  41. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  42. GRB 250221A: REM optical/NIR afterglow detection
  43. GRB 250221A: Enhanced Swift-XRT position
  44. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  45. GRB 250221A: Swift detection of a burst with an optical counterpart
  46. Fermi Gamma-ray Burst Monitor trigger 761788229/250220993 is not a GRB
  47. GRB 250220B: Fermi GBM Final Real-time Localization
  48. Fermi Gamma-ray Burst Monitor trigger 761782146/250220923 is not a GRB
  49. GRB 250220A: Fermi GBM Final Real-time Localization
  50. Konus-Wind detection of GRB 250217C (short)
  51. GRB 250219A: Swift/UVOT Upper Limits
  52. GRB 250219A: OHP/T193 optical upper limit
  53. GRB 250219A: NOT optical observations
  54. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  55. GRB 250219A: 1.6m Mephisto optical upper limits
  56. GRB 250219A: SVOM/VT optical counterpart
  57. GRB 250219A: Swift-XRT observations
  58. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  59. GRB 250219A: Swift ToO observations
  60. GRB 250219A: SVOM detection of a burst
  61. Konus-Wind detection of GRB 250215A / EP250215a
  62. GRB 250217C: Swift-XRT observations
  63. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  64. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  65. GRB 250217C: SVOM/GRM observation
  66. GRB 250217C: Tiled Swift observations
  67. GRB 250217C: Fermi GBM Observation
  68. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  69. IPN triangulation of GRB 250217C (short)
  70. GRB 250213A: Swift-XRT observations
  71. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  72. GRB 250216A: AstroSat CZTI detection
  73. GRB 250217C: AstroSat CZTI detection of a short burst
  74. Fermi GRB 250217C: Global MASTER-Net observations report
  75. GRB 250217C: Fermi GBM Final Real-time Localization
  76. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  77. Fermi GRB 250217A: Global MASTER-Net observations report
  78. GRANDMA/OPD observations of GRB250215A
  79. GRB 250217B: Fermi GBM Final Real-time Localization
  80. GRB 250217A: Fermi GBM Final Real-time Localization
  81. Fermi GRB 250216A: Global MASTER-Net observations report
  82. GRB 250215A / EP250215a: LCO detection of the afterglow
  83. GRB 250216A: Fermi GBM Final Real-time Localization
  84. GRB 250215A: Swift/UVOT Upper Limits
  85. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  86. EP250215a / GRB 250215A : GTC redshift z = 4.61
  87. GRB 250215A: Fermi GBM Observation
  88. EP250215a / GRB 250215A : NOT optical observations
  89. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  90. GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
  91. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  92. GRB 250215A: Swift-XRT refined Analysis
  93. GRB 250215A: SVOM/GRM observation
  94. EP250215a / GRB 250215A: AstroSat CZTI detection
  95. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  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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