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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"

22214 results found.

  1. GRB 250213A: Swift ToO observations
  2. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  3. EP250212a: Global MASTER-Net observations report
  4. GRB 250205A: Leavitt Observatory optical upper limit
  5. EP250207B: Chandra localization of the X-ray counterpart
  6. LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
  7. EP250207b: VLA radio upper limits
  8. GRB250101A: Radio upper limits from GMRT observations
  9. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  10. EP250207B: GTC z-band Observations
  11. Fermi GRB 250212A: Global MASTER-Net observations report
  12. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  13. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  14. Fermi trigger No 760945500: Global MASTER-Net observations report
  15. EP250207b: NOT optical counterpart candidate
  16. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  17. GRB 250211A: Swift ToO observations
  18. Integral GRB250211.89: Global MASTER-Net observations report
  19. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  20. GRB 250205A / EP250205A: radio detection with the VLA
  21. IceCube-250207A: One candidate from the Zwicky Transient Facility
  22. EP250207b: Tentative z-band brightening source
  23. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  24. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  25. Konus-Wind detection of GRB 250206A
  26. EP250207b: Liverpool Telescope possible optical counterpart
  27. EP250207b: Global MASTER-Net observations report
  28. Gemini-South spectroscopic redshift of EP250207b host galaxy candidate (z=0.082)
  29. GRB 250207A: Skynet optical afterglow observations
  30. LIGO/VIRGO/KAGRA S250206dm: AT 2025bbo spectroscopic observations with NIRES on Keck II
  31. LIGO/Virgo/KAGRA S250206dm: Gemini-North spectroscopic observation of AT2025bbo and its host galaxy
  32. EP250207b: Gemini GMOS-N z-band observations
  33. EP250207A: Upper limits from Fermi-GBM Observations
  34. GRB 250210A: INTEGRAL SPI-ACS detection
  35. EP250207b: a new X-ray transient detected by Einstein Probe
  36. Fermi GRB 250210A: Global MASTER-Net observations report
  37. LIGO/Virgo/KAGRA S250206dm: Upper limits from GECAM Observations
  38. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  39. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  40. IceCube Alert 250207.09: Global MASTER-Net observations report
  41. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  42. LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: MASTER observations and possible mother galaxy
  43. LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
  44. Fermi-LAT Gamma-ray Observations of IceCube-250207A
  45. GRB 250207A: 1.3m DFOT Optical observations
  46. LIGO/Virgo/KAGRA S250206dm: WFST follow-up observations
  47. GRB 250206A: Swift-XRT observations
  48. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A BOOTES-5 and 2.2m CAHA optical upper limits
  49. LIGO/Virgo/KAGRA S250206dm: further Pan-STARRS observations and one candidate AT2025bbo
  50. LIGO/Virgo/KAGRA S250207bg: Updated NED Galaxies in the Localization Volume
  51. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  52. GRB 250205A: 1.3m DFOT optical upper limit
  53. GRB 250206A: Tiled Swift observations
  54. LIGO/Virgo/KAGRA S250206dm: (Update-7) NED Galaxies in the Localization Volume
  55. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
  56. GRB 250207B: Swift-XRT observations
  57. IceCube-250203A: No transient candidates from the Zwicky Transient Facility
  58. LIGO/Virgo/KAGRA S250206dm: Spectroscopic Classification of AT2025bay and AT2025baz with Keck I/LRIS
  59. LIGO/Virgo/KAGRA S250206dm: Candidates from the Zwicky Transient Facility
  60. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates
  61. LIGO/Virgo/KAGRA S250206dm: MMT galaxy targeted observations
  62. EP-WXT trigger 01709131361: correction to GCN 39214
  63. EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
  64. LIGO/Virgo/KAGRA S250206dm: GOTO counterpart search update - AT2025bar
  65. EP-WXT trigger 01709131361 / LIGO/Virgo/KAGRA S250206dm: FTW optical and NIR observations
  66. GRB 250129A: ABObservatory SLOAN r’ afterglow detection
  67. GRB 250207A: REM IR afterglow detection
  68. LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap
  69. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS survey of the skymap for optical transients
  70. GRB 250207A: FRAM-Auger optical detection
  71. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits
  72. GRB 250207B: Tiled Swift observations
  73. LIGO/Virgo/KAGRA S250207bg: NED Galaxies in the Localization Volume
  74. GRB 250207A: REM optical afterglow detection
  75. GRB 250207A: Swift/UVOT Detection
  76. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limit for the Neutrino IceCube Candidate
  77. LIGO/Virgo/KAGRA S250206dm: GOTO observations of optical candidates AT 2025azn and AT 2025azm
  78. LIGO/Virgo/KAGRA S250206dm: SOAR galaxy targeted observations
  79. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS observations of AT2025azm and AT2025azn
  80. LIGO/Virgo/KAGRA S250206dm: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  81. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the AT 2025azn Optical Candidate
  82. GRB 250129A: Continued AbAO and Mondy optical observations
  83. LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
  84. GRB 250207A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  85. LIGO/Virgo/KAGRA S250206dm: Updated-6 NED Galaxies in the Localization Volume
  86. LIGO/Virgo/KAGRA S250206dm: Upper limits from Fermi-GBM Observations
  87. Fermi-LAT Gamma-ray Observations of IceCube-250203A
  88. LIGO/Virgo/KAGRA S250206dm: Coverage and upper limits from MAXI/GSC observations
  89. LIGO/Virgo/KAGRA S250206dm: Updated NED Galaxies in the Localization Volume
  90. LIGO/Virgo/KAGRA S250206dm: Two counterpart neutrino candidates from IceCube neutrino searches
  91. LIGO/Virgo/KAGRA S250206dm: NED Galaxies in the Localization Volume
  92. GRB 250205A: REM NIR upper limit
  93. EP250205a/GRB 250205A: FTW optical and NIR observations of the counterpart
  94. GRB 250205A: Swift/UVOT Upper Limits
  95. GRB 250205A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  96. GRB 250205A: Swift/XRT detection
  97. GRB 250205A: GOTO optical upper limits
  98. GRB 250205A: OHP/T193 optical counterpart candidate
  99. GRB 250205A: Liverpool Telescope optical counterpart candidate detection
  100. LIGO/Virgo/KAGRA S250205bk: NED Galaxies in the Localization Volume

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