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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"
  1. GRB 250214A: Fermi GBM Final Real-time Localization
  2. EP250212a: Xinglong optical upper limit
  3. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  4. GRB 250213A: SVOM detection of a burst
  5. EP250212a: Global MASTER-Net observations report
  6. GRB 250205A: VIRT Optical Upper Limit
  7. GRB 250205A: Leavitt Observatory optical upper limit
  8. GRB 250210A: GRBAlpha detection
  9. EP250207B: Chandra localization of the X-ray counterpart
  10. LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
  11. EP250207b: VLA radio upper limits
  12. EP250212a: Liverpool Telescope optical upper limits
  13. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  14. GRB250101A: Radio upper limits from GMRT observations
  15. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  16. EP250207B: GTC z-band Observations
  17. Fermi GRB 250212A: Global MASTER-Net observations report
  18. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  19. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  20. Fermi trigger No 760945500: Global MASTER-Net observations report
  21. EP250207b: NOT optical counterpart candidate
  22. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  23. GRB 250211B: A long GRB detected by INTEGRAL
  24. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  25. GRB 250211A: Swift ToO observations
  26. Integral GRB250211.89: Global MASTER-Net observations report
  27. GRB 250212A: Fermi GBM Final Real-time Localization
  28. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  29. LIGO/Virgo/KAGRA S250211be: Updated Sky localization
  30. GRB 250207A: Fermi GBM Observation
  31. GRB 250206A: Fermi GBM Observation
  32. GRB 250205A / EP250205A: radio detection with the VLA
  33. IceCube-250207A: One candidate from the Zwicky Transient Facility
  34. EP250207b: Tentative z-band brightening source
  35. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  36. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  37. Konus-Wind detection of GRB 250207A
  38. Konus-Wind detection of GRB 250206A
  39. GRB 250210A: SVOM/GRM observation of a long burst
  40. EP250207b: Liverpool Telescope possible optical counterpart
  41. EP250207b: Global MASTER-Net observations report
  42. Fermi Gamma-ray Burst Monitor trigger 760945500/250211240 is not a GRB
  43. Gemini-South spectroscopic redshift of EP250207b host galaxy candidate (z=0.082)
  44. LIGO/Virgo/KAGRA S250211be: Identification of a GW compact binary merger candidate
  45. LIGO/Virgo/KAGRA S250211aa: Updated Sky localization and EM Bright Classification
  46. LIGO/Virgo/KAGRA S250211aa: Identification of a GW compact binary merger candidate
  47. GRB 250207A: Skynet optical afterglow observations
  48. LIGO/VIRGO/KAGRA S250206dm: AT 2025bbo spectroscopic observations with NIRES on Keck II
  49. LIGO/Virgo/KAGRA S250206dm: Gemini-North spectroscopic observation of AT2025bbo and its host galaxy
  50. GRB 241128A: VIRT Optical Upper Limit
  51. EP250207b: Gemini GMOS-N z-band observations
  52. EP250207A: Upper limits from Fermi-GBM Observations
  53. GRB 250210A: INTEGRAL SPI-ACS detection
  54. GRB 250210A: AstroSat CZTI detection
  55. EP250207b: a new X-ray transient detected by Einstein Probe
  56. LIGO/Virgo/KAGRA S250206dm: MASTER detection AT2025bbo
  57. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  58. Fermi GRB 250210A: Global MASTER-Net observations report
  59. GRB 250210A: Fermi GBM Final Real-time Localization
  60. LIGO/Virgo/KAGRA S250206dm: Upper limits from GECAM Observations
  61. IceCube-250207A: Upper limits from a search for additional neutrino events in IceCube
  62. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  63. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  64. IceCube Alert 250207.09: Global MASTER-Net observations report
  65. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  66. GRB 250204B: GRBAlpha detection
  67. GRB 250204A: GRBAlpha detection
  68. LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: MASTER observations and possible mother galaxy
  69. LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
  70. Fermi-LAT Gamma-ray Observations of IceCube-250207A
  71. GRB 250207A: 1.3m DFOT Optical observations
  72. LIGO/Virgo/KAGRA S250206dm: WFST follow-up observations
  73. GRB 250206A: Swift-XRT observations
  74. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A BOOTES-5 and 2.2m CAHA optical upper limits
  75. GRB 250129A: GRANDMA Continued Afterglow Detection
  76. GRB 250207A: Swift-BAT refined analysis
  77. LIGO/Virgo/KAGRA S250206dm: further Pan-STARRS observations and one candidate AT2025bbo
  78. LIGO/Virgo/KAGRA S250207bg: Updated NED Galaxies in the Localization Volume
  79. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  80. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  81. GRB 250205A: 1.3m DFOT optical upper limit
  82. GRB 250206A: Tiled Swift observations
  83. LIGO/Virgo/KAGRA S250118az: Updated Sky localization
  84. LIGO/Virgo/KAGRA S250208ad: Updated Sky localization
  85. GRB 250206A: EIRSAT-1 GMOD Detection
  86. LIGO/Virgo/KAGRA S250206dm: (Update-7) NED Galaxies in the Localization Volume
  87. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
  88. GRB 250206A: Fermi-LAT detection
  89. GRB 250207B: Swift-XRT observations
  90. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  91. IceCube-250203A: No transient candidates from the Zwicky Transient Facility
  92. LIGO/Virgo/KAGRA S250206dm: Spectroscopic Classification of AT2025bay and AT2025baz with Keck I/LRIS
  93. LIGO/Virgo/KAGRA S250206dm: Candidates from the Zwicky Transient Facility
  94. LIGO/Virgo/KAGRA S250206dm: ePESSTO+ classification of AT2025bar
  95. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates
  96. GRB 250208A: Fermi GBM Final Real-time Localization
  97. EP250207a: EP-WXT detection and XRT follow-up observation
  98. LIGO/Virgo/KAGRA S250208ad: Identification of a GW compact binary merger candidate
  99. LIGO/Virgo/KAGRA S250206dm: MMT galaxy targeted observations
  100. GRB 250207A: Swift-XRT refined Analysis

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