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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"

2686 results found.

  1. IceCube-250416A - IceCube observation of a high-energy neutrino candidate track-like event
  2. EP250227a: Further NOT optical observations
  3. IceCube-250406A - IceCube observation of a high-energy neutrino candidate track-like event
  4. GRB 250331C Swift-BAT refined analysis
  5. IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
  6. GRB 250322B possible detection by the AstroSat Satellite
  7. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  8. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  9. IceCube-250330A - IceCube observation of a high-energy neutrino candidate track-like event
  10. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  11. GRB 250329A: SVOM/VT optical counterpart confirmation
  12. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  13. GRB 250317B: NOT optical observations suggest an optical plateau phase
  14. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  15. SVOM/MXT upper limit on GRB 250314A
  16. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  17. EP trigger ID 01709061302: Lick/Kast spectroscopy with the 3 m Shane telescope
  18. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  19. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  20. GRB 250309B / AT2025dws: SAO RAS optical observations
  21. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  22. EP250304a: MeerKAT detection of a possible radio counterpart
  23. GRB250101A: Radio upper limits from VLA observations
  24. IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
  25. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  26. GRB 250221A: EP-FXT detection of the X-ray afterglow
  27. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  28. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  29. GRB 250221A: VLT/X-shooter redshift z = 0.768
  30. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  31. EP250212a: FTW optical and NIR upper limits
  32. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  33. GRB250101A: Radio upper limits from GMRT observations
  34. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  35. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  36. EP250207b: Liverpool Telescope possible optical counterpart
  37. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  38. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  39. LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: MASTER observations and possible mother galaxy
  40. LIGO/Virgo/KAGRA S250206dm: further Pan-STARRS observations and one candidate AT2025bbo
  41. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates
  42. EP250207a: EP-WXT detection and XRT follow-up observation
  43. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A & "Time Machine" Effect.
  44. EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
  45. LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap
  46. GRB 250207A: FRAM-Auger optical detection
  47. IceCube-250207A - IceCube observation of a high-energy neutrino candidate track-like event
  48. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the AT 2025azn Optical Candidate
  49. LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
  50. IceCube-250203A - IceCube observation of a high-energy neutrino candidate track-like event
  51. GRB 250128B: VLA possible radio detection
  52. GRB 250128B: VLT/HAWKI near-infrared observations
  53. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  54. ATCA detection of possible radio counterpart to GRB 250114A
  55. EP250108a: optical follow-up observations with the Liverpool Telescope
  56. EP250108a: further NOT optical observations
  57. GRB 250108A: Swift/XRT afterglow fading
  58. GRB 250109A: Fermi GBM Observation
  59. GRB 250108B: Gemini-North likely redshift z = 2.197
  60. IceCube-250102A - IceCube observation of a high-energy neutrino candidate track-like event
  61. IceCube-250101A - IceCube observation of a high-energy neutrino candidate track-like event
  62. GRB 241229B: CrAO ZTSh possible optical counterpart of SVOM/VT confirmation
  63. GRB 241228B: GOTO possible optical counterpart candidate
  64. IceCube-241224A - IceCube observation of a high-energy neutrino candidate track-like event
  65. GRB 241223A: GOTO optical observations summary
  66. GRB 241105A: JWST photometric observations of the host galaxy
  67. GRB 241209B: host galaxy detection and GTC/OSIRIS+ spectroscopy
  68. GRB 241218A: Swift-BAT refined analysis
  69. EP 241217a: NIR detection with P200/WIRC
  70. EP 241217a: Possible J-band detection with WINTER
  71. EP241217a: Kinder optical follow-up observations
  72. EP241107a: VLA Radio Observation
  73. GRB 241212A: Fermi GBM detection
  74. GRB 241206C: GRBAlpha detection
  75. LIGO/Virgo/KAGRA S241102br: continued GRAWITA observations and detection of an optical transient (AT2024adip)
  76. EP241113a: Keck/LRIS spectroscopic observation and tentative redshift
  77. EP241201a: 1.6m Mephisto Optical Upper Limits
  78. GRB 241201A: GRBAlpha detection
  79. EP241202b: Kinder optical counterpart candidate
  80. EP241201a: Kinder optical counterpart candidate
  81. Swift-XRT observations of IceCube -241127A
  82. IceCube-241127A: IceCube observation of a high-energy neutrino candidate track-like event
  83. EP241125a: EP detection of an X-ray transient
  84. Konus-Wind detection of GRB 241117A
  85. IPN triangulation of GRB 241117A
  86. EP241021a and EP241026b: Keck/LRIS spectroscopic observations
  87. EP trigger ID 01709065118: Keck/LRIS spectroscopic observations
  88. GRB 241120A: Mondy and AbAO optical observations
  89. GRB 241113A: Possible ATCA Radio detection
  90. EP241115a/GRB 241115D: Swift/XRT follow-up observation
  91. EP 241113a: LBT possible optical counterpart
  92. IceCube-241113A - IceCube observation of a high-energy neutrino candidate track-like event
  93. LIGO/Virgo/KAGRA S241109bn: ATLAS observations and discovery of the potential counterpart AT2024aawt
  94. GRB 241030A: Mondy optical observations
  95. LIGO/Virgo/KAGRA S241102br: OHP/T193 optical observations
  96. EP241101a: Possible detection of an optical counterpart with FTW
  97. GRB 241030A / EP241030a: GMG possible spectroscopic redshift at z ~ 1.4
  98. GRB 241030A: detection of the bright optical counterpart in ATLAS forced photometry
  99. GRB 241030A: Keck/LRIS spectroscopic redshift z = 1.411
  100. EP 241026b: LBT possible optical counterpart (brightening source)

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