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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"

20958 results found.

  1. GRB 250225B: VLT optical and near-infrared candidate counterpart
  2. GRB 250225B: VLT/FORS2 candidate optical afterglow
  3. GRB 250221A: EP-FXT detection of the X-ray afterglow
  4. EP250226a/GRB 250226A: GSP detects optical counterpart
  5. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  6. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  7. EP250226a: Global MASTER-Net observations report
  8. Swift GRB 250225B: Global MASTER-Net observations report
  9. Fermi GRB 250226A: Global MASTER-Net observations report
  10. Fermi trigger No 762205158: Global MASTER-Net observations report
  11. EP250225a: Global MASTER-Net observations report
  12. EP250225a: GSP optical upper limit
  13. EP250225a: Einstein Probe detected of a fast X-ray transient
  14. Fermi GRB 250225A: Global MASTER-Net observations report
  15. EP250223a: GROWTH-India Telescope optical observations
  16. EP250215A: J band upper limit by SYSU 80cm telescope
  17. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  18. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  19. EP250223a: Kinder optical follow-up observations
  20. GRB 250207a: ATCA Radio Upper Limits
  21. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  22. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  23. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  24. EP250223a: GOTO optical afterglow detections
  25. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  26. EP250223a: REM NIR upper limit
  27. EP250223a: TRT optical afterglow observation
  28. EP250223a: refined analysis of the EP-WXT and FXT observations
  29. EP250223a: 1.6m Mephisto and 50cm array observations
  30. EP250223a: SVOM/VT optical observation
  31. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  32. EP250223a: OASDG optical observations
  33. EP250223a: LCO detection of the afterglow
  34. EP250223a: NOT redshift z = 2.756
  35. EP250223a: NOT optical afterglow candidate
  36. EP250223a: Global MASTER-Net observations report
  37. GRB 250221A: VLA radio detection
  38. Fermi GRB 250223A: Global MASTER-Net observations report
  39. Fermi trigger No 762020305: Global MASTER-Net observations report
  40. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  41. GRB 250221A: continued Mondy optical observations, brightening afterglow
  42. GRB 250221A: Optical counterpart detection by LCO.
  43. GRB 250221A: Mondy optical observations
  44. GRB 250221A: Assy optical observations
  45. EP250220a: FTW optical and NIR observations and upper limits
  46. EP250220a: EP-FXT follow-up observations
  47. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  48. Fermi trigger No 761805304: Global MASTER-Net observations report
  49. GRB 250221A: NOT optical observations
  50. GRB 250221A: 1.6m Mephisto optical detection
  51. GRB 250221A: Swift/UVOT Detection
  52. EP250220a: Liverpool Telescope upper limits
  53. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  54. GRB 250221A: REM optical/NIR afterglow detection
  55. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  56. EP250220a: 1.6m Mephisto observations
  57. EP250220a: Optical upper limit with Kinder observations
  58. Swift GRB250221.15: Global MASTER-Net observations report
  59. EP250220a: Global MASTER-Net observations report
  60. GRB 250219A: Swift/UVOT Upper Limits
  61. GRB 250219A: OHP/T193 optical upper limit
  62. GRB 250219A: NOT optical observations
  63. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  64. GRB 250219A: 1.6m Mephisto optical upper limits
  65. GRB 250219A: SVOM/VT optical counterpart
  66. GRB 250219A: Swift-XRT observations
  67. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  68. GRB 250219A: Swift ToO observations
  69. GRB 250217C: Swift-XRT observations
  70. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  71. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  72. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  73. GRB 250217C: Tiled Swift observations
  74. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  75. GRB 250213A: Swift-XRT observations
  76. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  77. Fermi GRB 250217C: Global MASTER-Net observations report
  78. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  79. Fermi GRB 250217A: Global MASTER-Net observations report
  80. GRANDMA/OPD observations of GRB250215A
  81. Fermi GRB 250216A: Global MASTER-Net observations report
  82. GRB 250215A / EP250215a: LCO detection of the afterglow
  83. EP250212a: FTW optical and NIR upper limits
  84. GRB 250215A: Swift/UVOT Upper Limits
  85. EP250215a / GRB 250215A : NOT optical observations
  86. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  87. LIGO/Virgo/KAGRA S250206dm: MASTER LC AT2025bbo
  88. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  89. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  90. EP250215a: Global MASTER-Net observations report
  91. EP250215A/GRB 250215A: INTEGRAL SPI-ACS detection
  92. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  93. Fermi GRB 250215A: Global MASTER-Net observations report
  94. Fermi trigger No 761206993: Global MASTER-Net observations report
  95. GRB 250213A：SVOM/VT optical candidate
  96. Fermi GRB 250214A: Global MASTER-Net observations report
  97. GRB 250213A: Swift ToO observations
  98. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  99. EP250212a: Global MASTER-Net observations report
  100. GRB 250205A: Leavitt Observatory optical upper limit

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