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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"

24705 results found.

  1. EP250223a: Einstein Probe detection of an X-ray transient
  2. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  3. GRB 250221A: Optical counterpart detection by LCO.
  4. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  5. GRB 250221A: GRANDMA/TAROT Detection
  6. GRB 250221A: Swift-XRT refined Analysis
  7. GRB 250221A: NOT optical observations
  8. GRB 250221A: 1.6m Mephisto optical detection
  9. GRB 250221A: AKO Optical Upper Limit
  10. GRB 250221A: Swift/UVOT Detection
  11. EP250220a: Liverpool Telescope upper limits
  12. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  13. GRB 250221A: REM optical/NIR afterglow detection
  14. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  15. GRB 250221A: Enhanced Swift-XRT position
  16. EP250220a: 1.6m Mephisto observations
  17. EP250220a: Liverpool Telescope optical upper limits
  18. EP250220a: Optical upper limit with Kinder observations
  19. SVOM trigger sb25022102 is not an astrophysical event
  20. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  21. GRB 250221A: Swift detection of a burst with an optical counterpart
  22. Swift GRB250221.15: Global MASTER-Net OT detection
  23. EP250220a: Xinglong optical upper limit
  24. GRB 250219A: Swift/UVOT Upper Limits
  25. GRB 250219A: OHP/T193 optical upper limit
  26. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  27. GRB 250219A: 1.6m Mephisto optical upper limits
  28. GRB 250219A: Swift-XRT observations
  29. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  30. Konus-Wind detection of GRB 250215A / EP250215a
  31. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  32. GRB 250217C: Swift-XRT observations
  33. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  34. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  35. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  36. GRB 250217C: SVOM/GRM observation
  37. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  38. SVOM/sb25021804: SVOM detection of a long X-ray transient
  39. GRB 250213A: Swift-XRT observations
  40. GRB 250216A: AstroSat CZTI detection
  41. GRB 250217C: AstroSat CZTI detection of a short burst
  42. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  43. GRANDMA/OPD observations of GRB250215A
  44. GRB 250215A / EP250215a: LCO detection of the afterglow
  45. GRB 250215A: Swift/UVOT Upper Limits
  46. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  47. GRB 250215A: Fermi GBM Observation
  48. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  49. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  50. GRB 250215A: Swift-XRT refined Analysis
  51. GRB 250215A: SVOM/GRM observation
  52. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  53. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  54. EP250207b: Xinglong optical upper limit
  55. EP250212a: Xinglong optical upper limit
  56. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  57. EP250212a: Global MASTER-Net observations report
  58. GRB 250205A: VIRT Optical Upper Limit
  59. GRB 250205A: Leavitt Observatory optical upper limit
  60. EP250207B: Chandra localization of the X-ray counterpart
  61. EP250212a: Liverpool Telescope optical upper limits
  62. GRB250101A: Radio upper limits from GMRT observations
  63. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  64. EP250207B: GTC z-band Observations
  65. Fermi GRB 250212A: Global MASTER-Net observations report
  66. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  67. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  68. Fermi trigger No 760945500: Global MASTER-Net observations report
  69. EP250207b: NOT optical counterpart candidate
  70. GRB 250211B: A long GRB detected by INTEGRAL
  71. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  72. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  73. LIGO/Virgo/KAGRA S250211be: Updated Sky localization
  74. GRB 250207A: Fermi GBM Observation
  75. GRB 250206A: Fermi GBM Observation
  76. GRB 250205A / EP250205A: radio detection with the VLA
  77. EP250207b: Tentative z-band brightening source
  78. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  79. Konus-Wind detection of GRB 250206A
  80. GRB 250210A: SVOM/GRM observation of a long burst
  81. EP250207b: Liverpool Telescope possible optical counterpart
  82. LIGO/Virgo/KAGRA S250211be: Identification of a GW compact binary merger candidate
  83. LIGO/Virgo/KAGRA S250211aa: Updated Sky localization and EM Bright Classification
  84. LIGO/Virgo/KAGRA S250211aa: Identification of a GW compact binary merger candidate
  85. GRB 250207A: Skynet optical afterglow observations
  86. GRB 241128A: VIRT Optical Upper Limit
  87. EP250207b: Gemini GMOS-N z-band observations
  88. EP250207A: Upper limits from Fermi-GBM Observations
  89. EP250207b: a new X-ray transient detected by Einstein Probe
  90. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  91. LIGO/Virgo/KAGRA S250206dm: Upper limits from GECAM Observations
  92. IceCube-250207A: Upper limits from a search for additional neutrino events in IceCube
  93. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  94. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  95. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  96. LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
  97. Fermi-LAT Gamma-ray Observations of IceCube-250207A
  98. GRB 250207A: 1.3m DFOT Optical observations
  99. LIGO/Virgo/KAGRA S250206dm: WFST follow-up observations
  100. GRB 250206A: Swift-XRT observations

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