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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').

19109 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. GRB 250207A: 1.3m DFOT Optical observations
  4. LIGO/Virgo/KAGRA S250206dm: WFST follow-up observations
  5. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A BOOTES-5 and 2.2m CAHA optical upper limits
  6. GRB 250129A: GRANDMA Continued Afterglow Detection
  7. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  8. GRB 250205A: 1.3m DFOT optical upper limit
  9. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
  10. GRB 250206A: Fermi-LAT detection
  11. GRB 250207B: Swift-XRT observations
  12. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  13. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates
  14. LIGO/Virgo/KAGRA S250208ad: Identification of a GW compact binary merger candidate
  15. LIGO/Virgo/KAGRA S250206dm: MMT galaxy targeted observations
  16. EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
  17. GRB 250207A: Enhanced Swift-XRT position
  18. LIGO/Virgo/KAGRA S250206dm: GOTO counterpart search update - AT2025bar
  19. GRB 250129A: ABObservatory SLOAN r’ afterglow detection
  20. GRB 250207A: REM IR afterglow detection
  21. LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap
  22. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits
  23. IGO/Virgo/KAGRA S250206dm: Virtual Telescope Project upper limit for the Neutrino IceCube Candidate
  24. GRB 250207A: REM optical afterglow detection
  25. LIGO/Virgo/KAGRA S250207bg: Identification of a GW compact binary merger candidate
  26. GRB 250207A: Swift/UVOT Detection
  27. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limit for the Neutrino IceCube Candidate
  28. LIGO/Virgo/KAGRA S250206dm: GOTO observations of optical candidates AT 2025azn and AT 2025azm
  29. LIGO/Virgo/KAGRA S250206dm: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  30. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the AT 2025azn Optical Candidate
  31. GRB 250129A: Continued AbAO and Mondy optical observations
  32. LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
  33. GRB 250207A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  34. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  35. GRB 250207A: Swift detection of a burst with optical counterpart
  36. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  37. LIGO/Virgo/KAGRA S250206dm: Identification of a GW compact binary merger candidate
  38. GRB 250205A: Fermi GBM Observation
  39. GRB 250205A: REM NIR upper limit
  40. GRB 250205A: Swift/UVOT Upper Limits
  41. EP250205a/GRB 250205A: Einstein Probe observation
  42. GRB 250127C: SVOM/GRM observation of a burst
  43. GRB 250204B: SVOM/GRM observation of a likely short burst
  44. GRB 250205A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  45. GRB 250205A: Redshift from OSIRIS+/GTC z = 3.55
  46. GRB250205A: SVOM/VT optical afterglow detection
  47. GRB 250205A: OHP/T193 optical counterpart candidate
  48. LIGO/Virgo/KAGRA S250205ee: Identification of a GW compact binary merger candidate
  49. GRB 250205A: SVOM detection of a burst
  50. Konus-Wind detection of GRB 250201A
  51. IPN triangulation of GRB 250201A
  52. Konus-Wind detection of GRB 250202B
  53. LIGO/Virgo/KAGRA S250205bk: Identification of a GW compact binary merger candidate
  54. IPN triangulation of GRB 250202B
  55. GRB 250129A: LCO late afterglow detection
  56. GRB 250129A: AbAO AS-32 and Mondy AZT-33IK optical observations
  57. LIGO/Virgo/KAGRA S250204ax: Identification of a GW compact binary merger candidate
  58. GRB 250129A: COLIBRÍ/DDRAGO Afterglow Detection
  59. GRB 250202B: NuSTAR detection of the prompt emission
  60. GRB 250202C: GRBAlpha detection
  61. GRB 250202B: Fermi GBM Detection
  62. GRB 250129a: Liverpool Telescope optical follow-up
  63. GRB 240129A: further SAO RAS optical observations
  64. GRB 250129A: 7DT Detection and Medium-band SED of Afterglow
  65. LIGO/Virgo/KAGRA S250202cu: Identification of a GW compact binary merger candidate
  66. GRB 250129A: SVOM/C-GFT optical observations
  67. Swift GRB250129A: MASTER 4 days observations report
  68. GRB 250129A: 1.3m DFOT Optical observations
  69. GRB 250129A: Skynet Continued Optical Observations
  70. GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
  71. GRB 250129A: SAO RAS optical observations
  72. GRB 250129A: COLIBRÍ Continuing Detection of the Afterglow
  73. GRB 250129A: optical photometry from Konkoly
  74. GRB 250129A: COLIBRÍ Optical Observations
  75. GRB 250129A: iTelescope optical observation
  76. GRB 250129a: Liverpool Telescope optical follow-up
  77. GRB 250129A: TNG NIR afterglow detection
  78. GRB 250129A: AKO Optical Afterglow Detection
  79. GRB 250129A: GRANDMA/TAROT optical afterglow detection
  80. GRB 250128B: SAO RAS Zeiss-1000 and CrAO ZTSh optical upper limits
  81. GRB 250128B: VLA radio upper limit
  82. Ep250125A: 1.3m DFOT optical upper limit
  83. GRB 250129A: Skynet optical observations
  84. GRB 250128B: TNG optical upper limit
  85. GRB 250129A: Swift/UVOT Detection
  86. GRB 250128B: VLT/HAWKI near-infrared observations
  87. GRB 250127A: CrAO and Terskol optical upper limits
  88. GRB 250129A: Enhanced Swift-XRT position
  89. GRB 250128B: NOT optical upper limit
  90. GRB 250128B: VLT/FORS2 optical observations
  91. GRB 250129A: REM optical/NIR afterglow detection
  92. GRB 250129A: OHP/T193 optical and spectroscopy observations
  93. GRB 250129A: Early afterglow detection by LCO.
  94. GRB 250128B: OHP/T193 optical upper limit
  95. GRB 250129A: LCO optical observations
  96. GRB 250129A: GOTO optical observations show brightening afterglow
  97. GRB 250129A: VLT/X-shooter redshift of z = 2.151
  98. GRB 250128B: Enhanced Swift-XRT position
  99. GRB 250129A: Swift detection of a burst with an optical counterpart
  100. Swift GRB 250129A: Global MASTER-Net OT detection

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