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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"

36363 results found.

  1. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  2. EP250226a/GRB 250226A: 1.6m Mephisto observations
  3. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  4. EP250226a/GRB 250226A: Kinder optical follow-up observations
  5. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  6. Fermi GRB 250226B: Global MASTER-Net observations report
  7. GRB 250226B: Fermi GBM Final Real-time Localization
  8. GRB 250225B: Fermi GBM Observation
  9. GRB 250221A: ATCA Detections and Upper Limits
  10. GRB 250225B: REM NIR upper limits
  11. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  12. Konus-Wind detection of GRB 250225B
  13. EP250223a: CrAO ZTSH optical observation
  14. GRB 250225B: VLT optical and near-infrared candidate counterpart
  15. GRB 250225B: VLT/FORS2 candidate optical afterglow
  16. GRB 250225B: SVOM/GRM observation of a long burst
  17. GRB 250226A: GECAM-B detection
  18. GRB 250221A: EP-FXT detection of the X-ray afterglow
  19. GRB 250214A: SVOM/GRM observation
  20. EP250226a/GRB 250226A: GSP detects optical counterpart
  21. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  22. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  23. EP250226a / GRB 250226A: TRT optical counterpart observation
  24. Swift GRB 250225B: Global MASTER-Net observations report
  25. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  26. Fermi GRB 250226A: Global MASTER-Net observations report
  27. GRB 250226A: Fermi GBM Final Real-time Localization
  28. Fermi GRB 250225A: Global MASTER-Net observations report
  29. GRB 250225B: Swift detection of a burst
  30. GRB 250221A: Swift-BAT refined analysis
  31. GRB 250223C: SVOM/GRM observation of a long burst
  32. GRB 250225A: Fermi GBM Final Real-time Localization
  33. GRB 250207a: ATCA Radio Upper Limits
  34. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  35. GRB 250119B: VZLUSAT-2 detection
  36. GRB 250223C: Fermi GBM Final Real-time Localization
  37. GRB 250202B: VZLUSAT-2 detection
  38. GRB 250219A: EP-FXT afterglow detection
  39. GRB 250222A: SVOM/GRM observation of a burst
  40. GRB 250210A: VZLUSAT-2 detection
  41. GRB 250206A: VZLUSAT-2 detection
  42. GRB 250221A: TNOT detection of the optical counterpart
  43. 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
  44. EP250223a: OASDG optical observations
  45. GRB 250223B: Fermi GBM Final Localization
  46. GRB 250221A: VLA radio detection
  47. Fermi GRB 250223A: Global MASTER-Net observations report
  48. GRB 250223A: Fermi GBM Final Real-time Localization
  49. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  50. GRB 250221A: continued Mondy optical observations, brightening afterglow
  51. GRB 250221A: Optical counterpart detection by LCO.
  52. GRB 250221A: Mondy optical observations
  53. Konus-Wind detection of GRB 250221A
  54. GRB 250221A: Assy optical observations
  55. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  56. GRB 250221A: VLT/X-shooter redshift z = 0.768
  57. GRB 250221A: GRANDMA/TAROT Detection
  58. Fermi Gamma-ray Burst Monitor trigger 761867337/250221909 is not a GRB
  59. GRB 250221A: Swift-XRT refined Analysis
  60. GRB 250221A: NOT optical observations
  61. GRB 250221A: 1.6m Mephisto optical detection
  62. GRB 250221A: AKO Optical Upper Limit
  63. GRB 250221A: Swift/UVOT Detection
  64. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  65. GRB 250221A: REM optical/NIR afterglow detection
  66. GRB 250221A: Enhanced Swift-XRT position
  67. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  68. GRB 250221A: Swift detection of a burst with an optical counterpart
  69. Fermi Gamma-ray Burst Monitor trigger 761788229/250220993 is not a GRB
  70. GRB 250220B: Fermi GBM Final Real-time Localization
  71. Fermi Gamma-ray Burst Monitor trigger 761782146/250220923 is not a GRB
  72. GRB 250220A: Fermi GBM Final Real-time Localization
  73. Konus-Wind detection of GRB 250217C (short)
  74. GRB 250219A: Swift/UVOT Upper Limits
  75. GRB 250219A: OHP/T193 optical upper limit
  76. GRB 250219A: NOT optical observations
  77. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  78. GRB 250219A: 1.6m Mephisto optical upper limits
  79. GRB 250219A: SVOM/VT optical counterpart
  80. GRB 250219A: Swift-XRT observations
  81. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  82. GRB 250219A: Swift ToO observations
  83. GRB 250219A: SVOM detection of a burst
  84. Konus-Wind detection of GRB 250215A / EP250215a
  85. GRB 250217C: Swift-XRT observations
  86. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  87. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  88. GRB 250217C: SVOM/GRM observation
  89. GRB 250217C: Tiled Swift observations
  90. GRB 250217C: Fermi GBM Observation
  91. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  92. IPN triangulation of GRB 250217C (short)
  93. GRB 250213A: Swift-XRT observations
  94. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  95. GRB 250216A: AstroSat CZTI detection
  96. GRB 250217C: AstroSat CZTI detection of a short burst
  97. Fermi GRB 250217C: Global MASTER-Net observations report
  98. GRB 250217C: Fermi GBM Final Real-time Localization
  99. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  100. Fermi GRB 250217A: Global MASTER-Net observations report

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