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GCN at AAS 245, Legacy Circulars Address Retirement. See news and announcements

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. Fermi trigger No 761206993: Global MASTER-Net observations report
  2. GRB 250213A:SVOM/VT optical candidate
  3. Fermi Gamma-ray Burst Monitor trigger 761206993/250214266 is not a GRB
  4. EP250207b: Xinglong optical upper limit
  5. Fermi GRB 250214A: Global MASTER-Net observations report
  6. GRB 250213A: Swift ToO observations
  7. GRB 250214A: Fermi GBM Final Real-time Localization
  8. EP250212a: Xinglong optical upper limit
  9. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  10. GRB 250213A: SVOM detection of a burst
  11. EP250212a: Global MASTER-Net observations report
  12. GRB 250205A: VIRT Optical Upper Limit
  13. GRB 250205A: Leavitt Observatory optical upper limit
  14. GRB 250210A: GRBAlpha detection
  15. EP250207B: Chandra localization of the X-ray counterpart
  16. LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
  17. EP250207b: VLA radio upper limits
  18. EP250212a: Liverpool Telescope optical upper limits
  19. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  20. GRB250101A: Radio upper limits from GMRT observations
  21. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  22. EP250207B: GTC z-band Observations
  23. Fermi GRB 250212A: Global MASTER-Net observations report
  24. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  25. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  26. Fermi trigger No 760945500: Global MASTER-Net observations report
  27. EP250207b: NOT optical counterpart candidate
  28. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  29. GRB 250211B: A long GRB detected by INTEGRAL
  30. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  31. GRB 250211A: Swift ToO observations
  32. Integral GRB250211.89: Global MASTER-Net observations report
  33. GRB 250212A: Fermi GBM Final Real-time Localization
  34. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  35. LIGO/Virgo/KAGRA S250211be: Updated Sky localization
  36. GRB 250207A: Fermi GBM Observation
  37. GRB 250206A: Fermi GBM Observation
  38. GRB 250205A / EP250205A: radio detection with the VLA
  39. IceCube-250207A: One candidate from the Zwicky Transient Facility
  40. EP250207b: Tentative z-band brightening source
  41. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  42. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  43. Konus-Wind detection of GRB 250207A
  44. Konus-Wind detection of GRB 250206A
  45. GRB 250210A: SVOM/GRM observation of a long burst
  46. EP250207b: Liverpool Telescope possible optical counterpart
  47. EP250207b: Global MASTER-Net observations report
  48. Fermi Gamma-ray Burst Monitor trigger 760945500/250211240 is not a GRB
  49. Gemini-South spectroscopic redshift of EP250207b host galaxy candidate (z=0.082)
  50. LIGO/Virgo/KAGRA S250211be: Identification of a GW compact binary merger candidate
  51. LIGO/Virgo/KAGRA S250211aa: Updated Sky localization and EM Bright Classification
  52. LIGO/Virgo/KAGRA S250211aa: Identification of a GW compact binary merger candidate
  53. GRB 250207A: Skynet optical afterglow observations
  54. LIGO/VIRGO/KAGRA S250206dm: AT 2025bbo spectroscopic observations with NIRES on Keck II
  55. LIGO/Virgo/KAGRA S250206dm: Gemini-North spectroscopic observation of AT2025bbo and its host galaxy
  56. GRB 241128A: VIRT Optical Upper Limit
  57. EP250207b: Gemini GMOS-N z-band observations
  58. EP250207A: Upper limits from Fermi-GBM Observations
  59. GRB 250210A: INTEGRAL SPI-ACS detection
  60. GRB 250210A: AstroSat CZTI detection
  61. EP250207b: a new X-ray transient detected by Einstein Probe
  62. LIGO/Virgo/KAGRA S250206dm: MASTER detection AT2025bbo
  63. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  64. Fermi GRB 250210A: Global MASTER-Net observations report
  65. GRB 250210A: Fermi GBM Final Real-time Localization
  66. LIGO/Virgo/KAGRA S250206dm: Upper limits from GECAM Observations
  67. IceCube-250207A: Upper limits from a search for additional neutrino events in IceCube
  68. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  69. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  70. IceCube Alert 250207.09: Global MASTER-Net observations report
  71. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  72. GRB 250204B: GRBAlpha detection
  73. GRB 250204A: GRBAlpha detection
  74. LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: MASTER observations and possible mother galaxy
  75. LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
  76. Fermi-LAT Gamma-ray Observations of IceCube-250207A
  77. GRB 250207A: 1.3m DFOT Optical observations
  78. LIGO/Virgo/KAGRA S250206dm: WFST follow-up observations
  79. GRB 250206A: Swift-XRT observations
  80. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A BOOTES-5 and 2.2m CAHA optical upper limits
  81. GRB 250129A: GRANDMA Continued Afterglow Detection
  82. GRB 250207A: Swift-BAT refined analysis
  83. LIGO/Virgo/KAGRA S250206dm: further Pan-STARRS observations and one candidate AT2025bbo
  84. LIGO/Virgo/KAGRA S250207bg: Updated NED Galaxies in the Localization Volume
  85. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  86. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  87. GRB 250205A: 1.3m DFOT optical upper limit
  88. GRB 250206A: Tiled Swift observations
  89. LIGO/Virgo/KAGRA S250118az: Updated Sky localization
  90. LIGO/Virgo/KAGRA S250208ad: Updated Sky localization
  91. GRB 250206A: EIRSAT-1 GMOD Detection
  92. LIGO/Virgo/KAGRA S250206dm: (Update-7) NED Galaxies in the Localization Volume
  93. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
  94. GRB 250206A: Fermi-LAT detection
  95. GRB 250207B: Swift-XRT observations
  96. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  97. IceCube-250203A: No transient candidates from the Zwicky Transient Facility
  98. LIGO/Virgo/KAGRA S250206dm: Spectroscopic Classification of AT2025bay and AT2025baz with Keck I/LRIS
  99. LIGO/Virgo/KAGRA S250206dm: Candidates from the Zwicky Transient Facility
  100. LIGO/Virgo/KAGRA S250206dm: ePESSTO+ classification of AT2025bar

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