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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.

Advanced Search Examples (click to copy):

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

20964 results found.

  1. GRB 250213A:SVOM/VT optical candidate
  2. Fermi GRB 250214A: Global MASTER-Net observations report
  3. GRB 250213A: Swift ToO observations
  4. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  5. EP250212a: Global MASTER-Net observations report
  6. GRB 250205A: Leavitt Observatory optical upper limit
  7. EP250207B: Chandra localization of the X-ray counterpart
  8. LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
  9. EP250207b: VLA radio upper limits
  10. GRB250101A: Radio upper limits from GMRT observations
  11. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  12. EP250207B: GTC z-band Observations
  13. Fermi GRB 250212A: Global MASTER-Net observations report
  14. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  15. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  16. Fermi trigger No 760945500: Global MASTER-Net observations report
  17. EP250207b: NOT optical counterpart candidate
  18. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  19. GRB 250211A: Swift ToO observations
  20. Integral GRB250211.89: Global MASTER-Net observations report
  21. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  22. GRB 250205A / EP250205A: radio detection with the VLA
  23. IceCube-250207A: One candidate from the Zwicky Transient Facility
  24. EP250207b: Tentative z-band brightening source
  25. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  26. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  27. EP250207b: Liverpool Telescope possible optical counterpart
  28. EP250207b: Global MASTER-Net observations report
  29. Gemini-South spectroscopic redshift of EP250207b host galaxy candidate (z=0.082)
  30. GRB 250207A: Skynet optical afterglow observations
  31. LIGO/VIRGO/KAGRA S250206dm: AT 2025bbo spectroscopic observations with NIRES on Keck II
  32. LIGO/Virgo/KAGRA S250206dm: Gemini-North spectroscopic observation of AT2025bbo and its host galaxy
  33. EP250207b: Gemini GMOS-N z-band observations
  34. EP250207A: Upper limits from Fermi-GBM Observations
  35. GRB 250210A: INTEGRAL SPI-ACS detection
  36. EP250207b: a new X-ray transient detected by Einstein Probe
  37. Fermi GRB 250210A: Global MASTER-Net observations report
  38. LIGO/Virgo/KAGRA S250206dm: Upper limits from GECAM Observations
  39. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  40. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  41. IceCube Alert 250207.09: Global MASTER-Net observations report
  42. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  43. LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: MASTER observations and possible mother galaxy
  44. LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
  45. Fermi-LAT Gamma-ray Observations of IceCube-250207A
  46. GRB 250207A: 1.3m DFOT Optical observations
  47. LIGO/Virgo/KAGRA S250206dm: WFST follow-up observations
  48. GRB 250206A: Swift-XRT observations
  49. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A BOOTES-5 and 2.2m CAHA optical upper limits
  50. GRB 250129A: GRANDMA Continued Afterglow Detection
  51. LIGO/Virgo/KAGRA S250206dm: further Pan-STARRS observations and one candidate AT2025bbo
  52. LIGO/Virgo/KAGRA S250207bg: Updated NED Galaxies in the Localization Volume
  53. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  54. GRB 250205A: 1.3m DFOT optical upper limit
  55. GRB 250206A: Tiled Swift observations
  56. LIGO/Virgo/KAGRA S250206dm: (Update-7) NED Galaxies in the Localization Volume
  57. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
  58. GRB 250207B: Swift-XRT observations
  59. IceCube-250203A: No transient candidates from the Zwicky Transient Facility
  60. LIGO/Virgo/KAGRA S250206dm: Spectroscopic Classification of AT2025bay and AT2025baz with Keck I/LRIS
  61. LIGO/Virgo/KAGRA S250206dm: Candidates from the Zwicky Transient Facility
  62. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates
  63. LIGO/Virgo/KAGRA S250206dm: MMT galaxy targeted observations
  64. EP-WXT trigger 01709131361: correction to GCN 39214
  65. EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
  66. LIGO/Virgo/KAGRA S250206dm: GOTO counterpart search update - AT2025bar
  67. EP-WXT trigger 01709131361 / LIGO/Virgo/KAGRA S250206dm: FTW optical and NIR observations
  68. GRB 250129A: ABObservatory SLOAN r’ afterglow detection
  69. GRB 250207A: REM IR afterglow detection
  70. LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap
  71. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS survey of the skymap for optical transients
  72. GRB 250207A: FRAM-Auger optical detection
  73. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits
  74. GRB 250207B: Tiled Swift observations
  75. LIGO/Virgo/KAGRA S250207bg: NED Galaxies in the Localization Volume
  76. GRB 250207A: REM optical afterglow detection
  77. GRB 250207A: Swift/UVOT Detection
  78. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limit for the Neutrino IceCube Candidate
  79. LIGO/Virgo/KAGRA S250206dm: GOTO observations of optical candidates AT 2025azn and AT 2025azm
  80. LIGO/Virgo/KAGRA S250206dm: SOAR galaxy targeted observations
  81. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS observations of AT2025azm and AT2025azn
  82. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the AT 2025azn Optical Candidate
  83. GRB 250129A: Continued AbAO and Mondy optical observations
  84. LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
  85. GRB 250207A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  86. LIGO/Virgo/KAGRA S250206dm: Updated-6 NED Galaxies in the Localization Volume
  87. LIGO/Virgo/KAGRA S250206dm: Upper limits from Fermi-GBM Observations
  88. Fermi-LAT Gamma-ray Observations of IceCube-250203A
  89. LIGO/Virgo/KAGRA S250206dm: Coverage and upper limits from MAXI/GSC observations
  90. LIGO/Virgo/KAGRA S250206dm: Updated NED Galaxies in the Localization Volume
  91. LIGO/Virgo/KAGRA S250206dm: Two counterpart neutrino candidates from IceCube neutrino searches
  92. LIGO/Virgo/KAGRA S250206dm: NED Galaxies in the Localization Volume
  93. GRB 250205A: REM NIR upper limit
  94. EP250205a/GRB 250205A: FTW optical and NIR observations of the counterpart
  95. GRB 250205A: Swift/UVOT Upper Limits
  96. GRB 250205A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  97. GRB 250205A: Swift/XRT detection
  98. GRB 250205A: GOTO optical upper limits
  99. GRB 250205A: OHP/T193 optical counterpart candidate
  100. GRB 250205A: Liverpool Telescope optical counterpart candidate detection

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