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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').
  1. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  2. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  3. IceCube Alert 250207.09: Global MASTER-Net observations report
  4. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  5. GRB 250204B: GRBAlpha detection
  6. GRB 250204A: GRBAlpha detection
  7. LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: MASTER observations and possible mother galaxy
  8. LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
  9. Fermi-LAT Gamma-ray Observations of IceCube-250207A
  10. GRB 250207A: 1.3m DFOT Optical observations
  11. LIGO/Virgo/KAGRA S250206dm: WFST follow-up observations
  12. GRB 250206A: Swift-XRT observations
  13. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A BOOTES-5 and 2.2m CAHA optical upper limits
  14. GRB 250129A: GRANDMA Continued Afterglow Detection
  15. GRB 250207A: Swift-BAT refined analysis
  16. LIGO/Virgo/KAGRA S250206dm: further Pan-STARRS observations and one candidate AT2025bbo
  17. LIGO/Virgo/KAGRA S250207bg: Updated NED Galaxies in the Localization Volume
  18. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  19. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  20. GRB 250205A: 1.3m DFOT optical upper limit
  21. GRB 250206A: Tiled Swift observations
  22. LIGO/Virgo/KAGRA S250118az: Updated Sky localization
  23. LIGO/Virgo/KAGRA S250208ad: Updated Sky localization
  24. GRB 250206A: EIRSAT-1 GMOD Detection
  25. LIGO/Virgo/KAGRA S250206dm: (Update-7) NED Galaxies in the Localization Volume
  26. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
  27. GRB 250206A: Fermi-LAT detection
  28. GRB 250207B: Swift-XRT observations
  29. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  30. IceCube-250203A: No transient candidates from the Zwicky Transient Facility
  31. LIGO/Virgo/KAGRA S250206dm: Spectroscopic Classification of AT2025bay and AT2025baz with Keck I/LRIS
  32. LIGO/Virgo/KAGRA S250206dm: Candidates from the Zwicky Transient Facility
  33. LIGO/Virgo/KAGRA S250206dm: ePESSTO+ classification of AT2025bar
  34. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates
  35. GRB 250208A: Fermi GBM Final Real-time Localization
  36. EP250207a: EP-WXT detection and XRT follow-up observation
  37. LIGO/Virgo/KAGRA S250208ad: Identification of a GW compact binary merger candidate
  38. LIGO/Virgo/KAGRA S250206dm: MMT galaxy targeted observations
  39. GRB 250207A: Swift-XRT refined Analysis
  40. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A & "Time Machine" Effect.
  41. EP-WXT trigger 01709131361: correction to GCN 39214
  42. EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
  43. GRB 250207A: Enhanced Swift-XRT position
  44. 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%
  45. LIGO/Virgo/KAGRA S250206dm: GOTO counterpart search update - AT2025bar
  46. EP-WXT trigger 01709131361 / LIGO/Virgo/KAGRA S250206dm: FTW optical and NIR observations
  47. GRB 250129A: ABObservatory SLOAN r’ afterglow detection
  48. GRB 250207A: REM IR afterglow detection
  49. LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap
  50. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS survey of the skymap for optical transients
  51. GRB 250207A: FRAM-Auger optical detection
  52. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits
  53. GRB 250207B: Tiled Swift observations
  54. LIGO/Virgo/KAGRA S250207bg: NED Galaxies in the Localization Volume
  55. Konus-Wind detection of GRB 250204B
  56. IGO/Virgo/KAGRA S250206dm: Virtual Telescope Project upper limit for the Neutrino IceCube Candidate
  57. IceCube-250207A - IceCube observation of a high-energy neutrino candidate track-like event
  58. GRB 250207A: REM optical afterglow detection
  59. LIGO/Virgo/KAGRA S250207bg: Identification of a GW compact binary merger candidate
  60. LIGO/Virgo/KAGRA S250206dm:GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  61. GRB 250207A: Swift/UVOT Detection
  62. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limit for the Neutrino IceCube Candidate
  63. LIGO/Virgo/KAGRA S250206dm: GOTO observations of optical candidates AT 2025azn and AT 2025azm
  64. LIGO/Virgo/KAGRA S250206dm: SOAR galaxy targeted observations
  65. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS observations of AT2025azm and AT2025azn
  66. LIGO/Virgo/KAGRA S250206dm: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  67. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the AT 2025azn Optical Candidate
  68. GRB 250129A: Continued AbAO and Mondy optical observations
  69. LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
  70. GRB 250207B: MAXI/GSC detection
  71. The EP-WXT trigger 01709131347 is likely a flaring star
  72. The EP-WXT trigger 01709131332 is likely a flaring star
  73. The EP-WXT trigger 01709131290 is likely a flaring star
  74. GRB 250207A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  75. LIGO/Virgo/KAGRA S250206dm: Updated-6 NED Galaxies in the Localization Volume
  76. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  77. LIGO/Virgo/KAGRA S250206dm: Upper limits from Fermi-GBM Observations
  78. GRB 250207A: Swift detection of a burst with optical counterpart
  79. GRB 250207A: Fermi GBM Final Real-time Localization
  80. Fermi-LAT Gamma-ray Observations of IceCube-250203A
  81. LIGO/Virgo/KAGRA S250206dm: Coverage and upper limits from MAXI/GSC observations
  82. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  83. LIGO/Virgo/KAGRA S250206dm: Updated NED Galaxies in the Localization Volume
  84. LIGO/Virgo/KAGRA S250206dm: Two counterpart neutrino candidates from IceCube neutrino searches
  85. LIGO/Virgo/KAGRA S250206dm: Identification of a GW compact binary merger candidate
  86. LIGO/Virgo/KAGRA S250206dm: NED Galaxies in the Localization Volume
  87. GRB 250206A: BALROG localization (Fermi Trigger 760564296 / GRB 250206827)
  88. GRB 250206A: Fermi GBM Final Real-time Localization
  89. GRB 250205A: Fermi GBM Observation
  90. GRB 250205A: REM NIR upper limit
  91. EP250205a/GRB 250205A: FTW optical and NIR observations of the counterpart
  92. GRB 250205A: Swift/UVOT Upper Limits
  93. LIGO/Virgo/KAGRA S250205ee: Updated Sky localization and Source Classification
  94. EP250205a/GRB 250205A: correction to the source localization
  95. EP250205a/GRB 250205A: Einstein Probe observation
  96. GRB 250127C: SVOM/GRM observation of a burst
  97. GRB 250204B: SVOM/GRM observation of a likely short burst
  98. GRB 250205A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  99. GRB 250205A: Swift/XRT detection
  100. GRB 250205A: Redshift from OSIRIS+/GTC z = 3.55

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