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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"

27320 results found.

  1. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  2. GRB 250202B: VZLUSAT-2 detection
  3. GRB 250222A: SVOM/GRM observation of a burst
  4. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  5. GRB 250206A: VZLUSAT-2 detection
  6. EP250223a: REM NIR upper limit
  7. EP250223a: TRT optical afterglow observation
  8. EP250223a: refined analysis of the EP-WXT and FXT observations
  9. EP250223a: 1.6m Mephisto and 50cm array observations
  10. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  11. 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
  12. EP250223a: OASDG optical observations
  13. EP250223a: LCO detection of the afterglow
  14. EP250223a: Swift/XRT localization
  15. EP250223a: NOT optical afterglow candidate
  16. EP250223a: Einstein Probe detection of an X-ray transient
  17. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  18. GRB 250221A: Optical counterpart detection by LCO.
  19. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  20. GRB 250221A: GRANDMA/TAROT Detection
  21. GRB 250221A: Swift-XRT refined Analysis
  22. GRB 250221A: NOT optical observations
  23. GRB 250221A: 1.6m Mephisto optical detection
  24. GRB 250221A: AKO Optical Upper Limit
  25. GRB 250221A: Swift/UVOT Detection
  26. EP250220a: Liverpool Telescope upper limits
  27. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  28. GRB 250221A: REM optical/NIR afterglow detection
  29. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  30. GRB 250221A: Enhanced Swift-XRT position
  31. EP250220a: 1.6m Mephisto observations
  32. EP250220a: Liverpool Telescope optical upper limits
  33. EP250220a: Optical upper limit with Kinder observations
  34. SVOM trigger sb25022102 is not an astrophysical event
  35. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  36. GRB 250221A: Swift detection of a burst with an optical counterpart
  37. Swift GRB250221.15: Global MASTER-Net OT detection
  38. EP250220a: Xinglong optical upper limit
  39. GRB 250219A: Swift/UVOT Upper Limits
  40. GRB 250219A: OHP/T193 optical upper limit
  41. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  42. GRB 250219A: 1.6m Mephisto optical upper limits
  43. GRB 250219A: Swift-XRT observations
  44. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  45. Konus-Wind detection of GRB 250215A / EP250215a
  46. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  47. GRB 250217C: Swift-XRT observations
  48. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  49. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  50. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  51. GRB 250217C: SVOM/GRM observation
  52. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  53. SVOM/sb25021804: SVOM detection of a long X-ray transient
  54. GRB 250213A: Swift-XRT observations
  55. GRB 250216A: AstroSat CZTI detection
  56. GRB 250217C: AstroSat CZTI detection of a short burst
  57. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  58. GRANDMA/OPD observations of GRB250215A
  59. GRB 250215A / EP250215a: LCO detection of the afterglow
  60. GRB 250215A: Swift/UVOT Upper Limits
  61. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  62. GRB 250215A: Fermi GBM Observation
  63. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  64. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  65. GRB 250215A: Swift-XRT refined Analysis
  66. GRB 250215A: SVOM/GRM observation
  67. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  68. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  69. EP250207b: Xinglong optical upper limit
  70. EP250212a: Xinglong optical upper limit
  71. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  72. EP250212a: Global MASTER-Net observations report
  73. GRB 250205A: VIRT Optical Upper Limit
  74. GRB 250205A: Leavitt Observatory optical upper limit
  75. EP250207B: Chandra localization of the X-ray counterpart
  76. EP250212a: Liverpool Telescope optical upper limits
  77. GRB250101A: Radio upper limits from GMRT observations
  78. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  79. EP250207B: GTC z-band Observations
  80. Fermi GRB 250212A: Global MASTER-Net observations report
  81. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  82. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  83. Fermi trigger No 760945500: Global MASTER-Net observations report
  84. EP250207b: NOT optical counterpart candidate
  85. GRB 250211B: A long GRB detected by INTEGRAL
  86. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  87. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  88. LIGO/Virgo/KAGRA S250211be: Updated Sky localization
  89. GRB 250207A: Fermi GBM Observation
  90. GRB 250206A: Fermi GBM Observation
  91. GRB 250205A / EP250205A: radio detection with the VLA
  92. EP250207b: Tentative z-band brightening source
  93. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  94. Konus-Wind detection of GRB 250206A
  95. GRB 250210A: SVOM/GRM observation of a long burst
  96. EP250207b: Liverpool Telescope possible optical counterpart
  97. LIGO/Virgo/KAGRA S250211be: Identification of a GW compact binary merger candidate
  98. LIGO/Virgo/KAGRA S250211aa: Updated Sky localization and EM Bright Classification
  99. LIGO/Virgo/KAGRA S250211aa: Identification of a GW compact binary merger candidate
  100. GRB 250207A: Skynet optical afterglow observations

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