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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.

Lucene Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

19138 results found.

  1. LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: MASTER observations and possible mother galaxy
  2. LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
  3. Fermi-LAT Gamma-ray Observations of IceCube-250207A
  4. GRB 250207A: 1.3m DFOT Optical observations
  5. LIGO/Virgo/KAGRA S250206dm: WFST follow-up observations
  6. GRB 250206A: Swift-XRT observations
  7. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A BOOTES-5 and 2.2m CAHA optical upper limits
  8. LIGO/Virgo/KAGRA S250206dm: further Pan-STARRS observations and one candidate AT2025bbo
  9. LIGO/Virgo/KAGRA S250207bg: Updated NED Galaxies in the Localization Volume
  10. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  11. GRB 250205A: 1.3m DFOT optical upper limit
  12. GRB 250206A: Tiled Swift observations
  13. LIGO/Virgo/KAGRA S250206dm: (Update-7) NED Galaxies in the Localization Volume
  14. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
  15. GRB 250207B: Swift-XRT observations
  16. IceCube-250203A: No transient candidates from the Zwicky Transient Facility
  17. LIGO/Virgo/KAGRA S250206dm: Spectroscopic Classification of AT2025bay and AT2025baz with Keck I/LRIS
  18. LIGO/Virgo/KAGRA S250206dm: Candidates from the Zwicky Transient Facility
  19. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates
  20. LIGO/Virgo/KAGRA S250206dm: MMT galaxy targeted observations
  21. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A & "Time Machine" Effect.
  22. EP-WXT trigger 01709131361: correction to GCN 39214
  23. EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
  24. CHIME/FRB source FRB 20250206A detected less than 1 minute after LIGO-Virgo-Kagra (LVK) S250206dm, however the probability of spatial coincidence is order 0.1%
  25. LIGO/Virgo/KAGRA S250206dm: GOTO counterpart search update - AT2025bar
  26. EP-WXT trigger 01709131361 / LIGO/Virgo/KAGRA S250206dm: FTW optical and NIR observations
  27. GRB 250129A: ABObservatory SLOAN r’ afterglow detection
  28. GRB 250207A: REM IR afterglow detection
  29. LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap
  30. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS survey of the skymap for optical transients
  31. GRB 250207A: FRAM-Auger optical detection
  32. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits
  33. GRB 250207B: Tiled Swift observations
  34. LIGO/Virgo/KAGRA S250207bg: NED Galaxies in the Localization Volume
  35. GRB 250207A: REM optical afterglow detection
  36. LIGO/Virgo/KAGRA S250206dm:GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  37. GRB 250207A: Swift/UVOT Detection
  38. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limit for the Neutrino IceCube Candidate
  39. LIGO/Virgo/KAGRA S250206dm: GOTO observations of optical candidates AT 2025azn and AT 2025azm
  40. LIGO/Virgo/KAGRA S250206dm: SOAR galaxy targeted observations
  41. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS observations of AT2025azm and AT2025azn
  42. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the AT 2025azn Optical Candidate
  43. GRB 250129A: Continued AbAO and Mondy optical observations
  44. LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
  45. GRB 250207A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  46. LIGO/Virgo/KAGRA S250206dm: Updated-6 NED Galaxies in the Localization Volume
  47. LIGO/Virgo/KAGRA S250206dm: Upper limits from Fermi-GBM Observations
  48. Fermi-LAT Gamma-ray Observations of IceCube-250203A
  49. LIGO/Virgo/KAGRA S250206dm: Coverage and upper limits from MAXI/GSC observations
  50. LIGO/Virgo/KAGRA S250206dm: Updated NED Galaxies in the Localization Volume
  51. LIGO/Virgo/KAGRA S250206dm: Two counterpart neutrino candidates from IceCube neutrino searches
  52. LIGO/Virgo/KAGRA S250206dm: NED Galaxies in the Localization Volume
  53. GRB 250205A: REM NIR upper limit
  54. EP250205a/GRB 250205A: FTW optical and NIR observations of the counterpart
  55. GRB 250205A: Swift/UVOT Upper Limits
  56. GRB 250205A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  57. GRB 250205A: Swift/XRT detection
  58. GRB 250205A: GOTO optical upper limits
  59. GRB 250205A: OHP/T193 optical counterpart candidate
  60. GRB 250205A: Liverpool Telescope optical counterpart candidate detection
  61. LIGO/Virgo/KAGRA S250205bk: NED Galaxies in the Localization Volume
  62. EP 250108A: Upper limits from Fermi-GBM Observations
  63. GRB 250129A: LCO late afterglow detection
  64. GRB 250129A: AbAO AS-32 and Mondy AZT-33IK optical observations
  65. GRB 250129A: COLIBRÍ/DDRAGO Afterglow Detection
  66. GRB 250129a: Liverpool Telescope optical follow-up
  67. GRB 240129A: further SAO RAS optical observations
  68. GRB 250129A: 7DT Detection and Medium-band SED of Afterglow
  69. GRB 250129A: SVOM/C-GFT optical observations
  70. Swift GRB250129A: MASTER 4 days observations report
  71. GRB 250201A: INTEGRAL SPI/ACS detection
  72. GRB 250129A: 1.3m DFOT Optical observations
  73. GRB 250129A: Liverpool Telescope observations suggest continued engine activity
  74. LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations
  75. GRB 250129A: Skynet Continued Optical Observations
  76. GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
  77. GRB 250129A: SAO RAS optical observations
  78. GRB 250129A: COLIBRÍ Continuing Detection of the Afterglow
  79. GRB 250129A: optical photometry from Konkoly
  80. GRB 250129A: COLIBRÍ Optical Observations
  81. GRB 250128B: VLA possible radio detection
  82. GRB 250129A: continued KAIT observations indicating steep decay after 28.5h
  83. GRB 250129A: NOT optical observations of continuining activity
  84. GRB 250129a: Liverpool Telescope optical follow-up
  85. GRB 250129A: GRANDMA/TAROT optical afterglow detection
  86. GRB 250128B: SAO RAS Zeiss-1000 and CrAO ZTSh optical upper limits
  87. GRB 250128B: VLA radio upper limit
  88. Ep250125A: 1.3m DFOT optical upper limit
  89. GRB 250129A: Skynet optical observations
  90. GRB 250129A: KAIT optical observations of the rebrightening around 5.1 hours
  91. GRB 250128B: Gemini-North optical extended source detection
  92. The EP-WXT trigger 01709131085: KAIT confirmation of the stellar flare
  93. GRB 250129A: Swift/UVOT Detection
  94. GRB 250128B: VLT/HAWKI near-infrared observations
  95. GRB 250127A: CrAO and Terskol optical upper limits
  96. GRB 250128B: VLT/FORS2 optical observations
  97. GRB 250129A: REM optical/NIR afterglow detection
  98. GRB 250129A: OHP/T193 optical and spectroscopy observations
  99. GRB 250129A: Early afterglow detection by LCO.
  100. GRB 250129A: LCO optical observations

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