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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').

19137 results found.

  1. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  2. GRB 250221A: continued Mondy optical observations, brightening afterglow
  3. GRB 250221A: Optical counterpart detection by LCO.
  4. GRB 250221A: Mondy optical observations
  5. GRB 250221A: Assy optical observations
  6. EP250220a: FTW optical and NIR observations and upper limits
  7. EP250220a: EP-FXT follow-up observations
  8. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  9. Fermi trigger No 761805304: Global MASTER-Net observations report
  10. GRB 250221A: NOT optical observations
  11. GRB 250221A: 1.6m Mephisto optical detection
  12. GRB 250221A: Swift/UVOT Detection
  13. EP250220a: Liverpool Telescope upper limits
  14. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  15. GRB 250221A: REM optical/NIR afterglow detection
  16. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  17. EP250220a: 1.6m Mephisto observations
  18. EP250220a: Optical upper limit with Kinder observations
  19. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  20. Swift GRB250221.15: Global MASTER-Net observations report
  21. EP250220a: Global MASTER-Net observations report
  22. GRB 250219A: Swift/UVOT Upper Limits
  23. GRB 250219A: OHP/T193 optical upper limit
  24. GRB 250219A: NOT optical observations
  25. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  26. GRB 250219A: 1.6m Mephisto optical upper limits
  27. GRB 250219A: SVOM/VT optical counterpart
  28. GRB 250219A: Swift-XRT observations
  29. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  30. GRB 250219A: Swift ToO observations
  31. GRB 250217C: Swift-XRT observations
  32. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  33. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  34. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  35. GRB 250217C: Tiled Swift observations
  36. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  37. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  38. GRB 250213A: Swift-XRT observations
  39. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  40. Fermi GRB 250217C: Global MASTER-Net observations report
  41. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  42. Fermi GRB 250217A: Global MASTER-Net observations report
  43. GRANDMA/OPD observations of GRB250215A
  44. Fermi GRB 250216A: Global MASTER-Net observations report
  45. GRB 250215A / EP250215a: LCO detection of the afterglow
  46. EP250212a: FTW optical and NIR upper limits
  47. GRB 250215A: Swift/UVOT Upper Limits
  48. EP250215a / GRB 250215A : NOT optical observations
  49. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  50. LIGO/Virgo/KAGRA S250206dm: MASTER LC AT2025bbo
  51. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  52. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  53. EP250215a: Global MASTER-Net observations report
  54. EP250215A/GRB 250215A: INTEGRAL SPI-ACS detection
  55. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  56. Fermi GRB 250215A: Global MASTER-Net observations report
  57. Fermi trigger No 761206993: Global MASTER-Net observations report
  58. GRB 250213A：SVOM/VT optical candidate
  59. Fermi GRB 250214A: Global MASTER-Net observations report
  60. GRB 250213A: Swift ToO observations
  61. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  62. EP250212a: Global MASTER-Net observations report
  63. GRB 250205A: Leavitt Observatory optical upper limit
  64. EP250207B: Chandra localization of the X-ray counterpart
  65. LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
  66. EP250207b: VLA radio upper limits
  67. GRB250101A: Radio upper limits from GMRT observations
  68. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  69. EP250207B: GTC z-band Observations
  70. Fermi GRB 250212A: Global MASTER-Net observations report
  71. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  72. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  73. Fermi trigger No 760945500: Global MASTER-Net observations report
  74. EP250207b: NOT optical counterpart candidate
  75. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  76. GRB 250211A: Swift ToO observations
  77. Integral GRB250211.89: Global MASTER-Net observations report
  78. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  79. GRB 250205A / EP250205A: radio detection with the VLA
  80. IceCube-250207A: One candidate from the Zwicky Transient Facility
  81. EP250207b: Tentative z-band brightening source
  82. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  83. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  84. EP250207b: Liverpool Telescope possible optical counterpart
  85. EP250207b: Global MASTER-Net observations report
  86. Gemini-South spectroscopic redshift of EP250207b host galaxy candidate (z=0.082)
  87. GRB 250207A: Skynet optical afterglow observations
  88. LIGO/VIRGO/KAGRA S250206dm: AT 2025bbo spectroscopic observations with NIRES on Keck II
  89. LIGO/Virgo/KAGRA S250206dm: Gemini-North spectroscopic observation of AT2025bbo and its host galaxy
  90. EP250207b: Gemini GMOS-N z-band observations
  91. EP250207A: Upper limits from Fermi-GBM Observations
  92. GRB 250210A: INTEGRAL SPI-ACS detection
  93. EP250207b: a new X-ray transient detected by Einstein Probe
  94. Fermi GRB 250210A: Global MASTER-Net observations report
  95. LIGO/Virgo/KAGRA S250206dm: Upper limits from GECAM Observations
  96. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  97. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  98. IceCube Alert 250207.09: Global MASTER-Net observations report
  99. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  100. LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: MASTER observations and possible mother galaxy

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