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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').

18787 results found.

  1. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  2. GRB 250221A: GRANDMA/TAROT Detection
  3. GRB 250221A: 1.6m Mephisto optical detection
  4. GRB 250221A: AKO Optical Upper Limit
  5. GRB 250221A: Swift/UVOT Detection
  6. EP250220a: Liverpool Telescope upper limits
  7. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  8. GRB 250221A: REM optical/NIR afterglow detection
  9. GRB 250221A: Enhanced Swift-XRT position
  10. EP250220a: 1.6m Mephisto observations
  11. EP250220a: Liverpool Telescope optical upper limits
  12. EP250220a: Optical upper limit with Kinder observations
  13. SVOM trigger sb25022102 is not an astrophysical event
  14. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  15. GRB 250221A: Swift detection of a burst with an optical counterpart
  16. Swift GRB250221.15: Global MASTER-Net OT detection
  17. EP250220a: Xinglong optical upper limit
  18. Konus-Wind detection of GRB 250217C (short)
  19. GRB 250219A: Swift/UVOT Upper Limits
  20. GRB 250219A: OHP/T193 optical upper limit
  21. GRB 250219A: NOT optical observations
  22. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  23. GRB 250219A: 1.6m Mephisto optical upper limits
  24. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  25. GRB 250219A: SVOM detection of a burst
  26. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  27. GRB 250217C: Swift-XRT observations
  28. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  29. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  30. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  31. GRB 250217C: SVOM/GRM observation
  32. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  33. SVOM/sb25021804: SVOM detection of a long X-ray transient
  34. GRANDMA/OPD observations of GRB250215A
  35. GRB 250215A / EP250215a: LCO detection of the afterglow
  36. GRB 250215A: Swift/UVOT Upper Limits
  37. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  38. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  39. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  40. GRB 250215A: SVOM/GRM observation
  41. EP250215a / GRB 250215A: AstroSat CZTI detection
  42. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  43. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  44. EP250207b: Xinglong optical upper limit
  45. EP250212a: Xinglong optical upper limit
  46. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  47. GRB 250205A: VIRT Optical Upper Limit
  48. GRB 250205A: Leavitt Observatory optical upper limit
  49. GRB 250210A: GRBAlpha detection
  50. EP250207B: Chandra localization of the X-ray counterpart
  51. EP250212a: Liverpool Telescope optical upper limits
  52. GRB250101A: Radio upper limits from GMRT observations
  53. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  54. EP250207B: GTC z-band Observations
  55. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  56. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  57. EP250207b: NOT optical counterpart candidate
  58. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  59. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  60. GRB 250205A / EP250205A: radio detection with the VLA
  61. EP250207b: Tentative z-band brightening source
  62. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  63. Konus-Wind detection of GRB 250207A
  64. Konus-Wind detection of GRB 250206A
  65. GRB 250210A: SVOM/GRM observation of a long burst
  66. EP250207b: Liverpool Telescope possible optical counterpart
  67. LIGO/Virgo/KAGRA S250211be: Identification of a GW compact binary merger candidate
  68. LIGO/Virgo/KAGRA S250211aa: Updated Sky localization and EM Bright Classification
  69. LIGO/Virgo/KAGRA S250211aa: Identification of a GW compact binary merger candidate
  70. GRB 250207A: Skynet optical afterglow observations
  71. GRB 241128A: VIRT Optical Upper Limit
  72. EP250207b: Gemini GMOS-N z-band observations
  73. EP250207b: a new X-ray transient detected by Einstein Probe
  74. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  75. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  76. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  77. GRB 250204B: GRBAlpha detection
  78. GRB 250204A: GRBAlpha detection
  79. LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: MASTER observations and possible mother galaxy
  80. LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
  81. GRB 250207A: 1.3m DFOT Optical observations
  82. LIGO/Virgo/KAGRA S250206dm: WFST follow-up observations
  83. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A BOOTES-5 and 2.2m CAHA optical upper limits
  84. GRB 250129A: GRANDMA Continued Afterglow Detection
  85. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  86. GRB 250205A: 1.3m DFOT optical upper limit
  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. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates
  92. LIGO/Virgo/KAGRA S250208ad: Identification of a GW compact binary merger candidate
  93. LIGO/Virgo/KAGRA S250206dm: MMT galaxy targeted observations
  94. EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
  95. GRB 250207A: Enhanced Swift-XRT position
  96. LIGO/Virgo/KAGRA S250206dm: GOTO counterpart search update - AT2025bar
  97. GRB 250129A: ABObservatory SLOAN r’ afterglow detection
  98. GRB 250207A: REM IR afterglow detection
  99. LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap
  100. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits

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