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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"

36347 results found.

  1. GRB 250226A: GECAM-B detection
  2. GRB 250221A: EP-FXT detection of the X-ray afterglow
  3. GRB 250214A: SVOM/GRM observation
  4. EP250226a/GRB 250226A: GSP detects optical counterpart
  5. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  6. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  7. EP250226a / GRB 250226A: TRT optical counterpart observation
  8. Swift GRB 250225B: Global MASTER-Net observations report
  9. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  10. Fermi GRB 250226A: Global MASTER-Net observations report
  11. GRB 250226A: Fermi GBM Final Real-time Localization
  12. Fermi GRB 250225A: Global MASTER-Net observations report
  13. GRB 250225B: Swift detection of a burst
  14. GRB 250221A: Swift-BAT refined analysis
  15. GRB 250223C: SVOM/GRM observation of a long burst
  16. GRB 250225A: Fermi GBM Final Real-time Localization
  17. GRB 250207a: ATCA Radio Upper Limits
  18. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  19. GRB 250119B: VZLUSAT-2 detection
  20. GRB 250223C: Fermi GBM Final Real-time Localization
  21. GRB 250202B: VZLUSAT-2 detection
  22. GRB 250219A: EP-FXT afterglow detection
  23. GRB 250222A: SVOM/GRM observation of a burst
  24. GRB 250210A: VZLUSAT-2 detection
  25. GRB 250206A: VZLUSAT-2 detection
  26. GRB 250221A: TNOT detection of the optical counterpart
  27. 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
  28. EP250223a: OASDG optical observations
  29. GRB 250223B: Fermi GBM Final Localization
  30. GRB 250221A: VLA radio detection
  31. Fermi GRB 250223A: Global MASTER-Net observations report
  32. GRB 250223A: Fermi GBM Final Real-time Localization
  33. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  34. GRB 250221A: continued Mondy optical observations, brightening afterglow
  35. GRB 250221A: Optical counterpart detection by LCO.
  36. GRB 250221A: Mondy optical observations
  37. Konus-Wind detection of GRB 250221A
  38. GRB 250221A: Assy optical observations
  39. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  40. GRB 250221A: VLT/X-shooter redshift z = 0.768
  41. GRB 250221A: GRANDMA/TAROT Detection
  42. Fermi Gamma-ray Burst Monitor trigger 761867337/250221909 is not a GRB
  43. GRB 250221A: Swift-XRT refined Analysis
  44. GRB 250221A: NOT optical observations
  45. GRB 250221A: 1.6m Mephisto optical detection
  46. GRB 250221A: AKO Optical Upper Limit
  47. GRB 250221A: Swift/UVOT Detection
  48. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  49. GRB 250221A: REM optical/NIR afterglow detection
  50. GRB 250221A: Enhanced Swift-XRT position
  51. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  52. GRB 250221A: Swift detection of a burst with an optical counterpart
  53. Fermi Gamma-ray Burst Monitor trigger 761788229/250220993 is not a GRB
  54. GRB 250220B: Fermi GBM Final Real-time Localization
  55. Fermi Gamma-ray Burst Monitor trigger 761782146/250220923 is not a GRB
  56. GRB 250220A: Fermi GBM Final Real-time Localization
  57. Konus-Wind detection of GRB 250217C (short)
  58. GRB 250219A: Swift/UVOT Upper Limits
  59. GRB 250219A: OHP/T193 optical upper limit
  60. GRB 250219A: NOT optical observations
  61. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  62. GRB 250219A: 1.6m Mephisto optical upper limits
  63. GRB 250219A: SVOM/VT optical counterpart
  64. GRB 250219A: Swift-XRT observations
  65. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  66. GRB 250219A: Swift ToO observations
  67. GRB 250219A: SVOM detection of a burst
  68. Konus-Wind detection of GRB 250215A / EP250215a
  69. GRB 250217C: Swift-XRT observations
  70. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  71. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  72. GRB 250217C: SVOM/GRM observation
  73. GRB 250217C: Tiled Swift observations
  74. GRB 250217C: Fermi GBM Observation
  75. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  76. IPN triangulation of GRB 250217C (short)
  77. GRB 250213A: Swift-XRT observations
  78. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  79. GRB 250216A: AstroSat CZTI detection
  80. GRB 250217C: AstroSat CZTI detection of a short burst
  81. Fermi GRB 250217C: Global MASTER-Net observations report
  82. GRB 250217C: Fermi GBM Final Real-time Localization
  83. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  84. Fermi GRB 250217A: Global MASTER-Net observations report
  85. GRANDMA/OPD observations of GRB250215A
  86. GRB 250217B: Fermi GBM Final Real-time Localization
  87. GRB 250217A: Fermi GBM Final Real-time Localization
  88. Fermi GRB 250216A: Global MASTER-Net observations report
  89. GRB 250215A / EP250215a: LCO detection of the afterglow
  90. GRB 250216A: Fermi GBM Final Real-time Localization
  91. GRB 250215A: Swift/UVOT Upper Limits
  92. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  93. EP250215a / GRB 250215A : GTC redshift z = 4.61
  94. GRB 250215A: Fermi GBM Observation
  95. EP250215a / GRB 250215A : NOT optical observations
  96. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  97. GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
  98. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  99. GRB 250215A: Swift-XRT refined Analysis
  100. GRB 250215A: SVOM/GRM observation

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