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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"

19091 results found.

  1. GRB 250219A: SVOM detection of a burst
  2. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  3. GRB 250217C: Swift-XRT observations
  4. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  5. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  6. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  7. GRB 250217C: SVOM/GRM observation
  8. GRB 250217C: Tiled Swift observations
  9. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  10. SVOM/sb25021804: SVOM detection of a long X-ray transient
  11. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  12. GRANDMA/OPD observations of GRB250215A
  13. GRB 250215A / EP250215a: LCO detection of the afterglow
  14. GRB 250215A: Swift/UVOT Upper Limits
  15. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  16. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  17. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  18. GRB 250215A: SVOM/GRM observation
  19. EP250215a / GRB 250215A: AstroSat CZTI detection
  20. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  21. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  22. EP250207b: Xinglong optical upper limit
  23. GRB 250213A: Swift ToO observations
  24. EP250212a: Xinglong optical upper limit
  25. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  26. GRB 250213A: SVOM detection of a burst
  27. GRB 250205A: VIRT Optical Upper Limit
  28. GRB 250205A: Leavitt Observatory optical upper limit
  29. EP250207B: Chandra localization of the X-ray counterpart
  30. EP250212a: Liverpool Telescope optical upper limits
  31. GRB250101A: Radio upper limits from GMRT observations
  32. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  33. EP250207B: GTC z-band Observations
  34. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  35. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  36. EP250207b: NOT optical counterpart candidate
  37. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  38. GRB 250211A: Swift ToO observations
  39. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  40. GRB 250206A: Fermi GBM Observation
  41. GRB 250205A / EP250205A: radio detection with the VLA
  42. EP250207b: Tentative z-band brightening source
  43. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  44. GRB 250210A: SVOM/GRM observation of a long burst
  45. EP250207b: Liverpool Telescope possible optical counterpart
  46. LIGO/Virgo/KAGRA S250211aa: Identification of a GW compact binary merger candidate
  47. GRB 250207A: Skynet optical afterglow observations
  48. GRB 241128A: VIRT Optical Upper Limit
  49. EP250207b: Gemini GMOS-N z-band observations
  50. EP250207b: a new X-ray transient detected by Einstein Probe
  51. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  52. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  53. LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
  54. Fermi-LAT Gamma-ray Observations of IceCube-250207A
  55. GRB 250207A: 1.3m DFOT Optical observations
  56. LIGO/Virgo/KAGRA S250206dm: WFST follow-up observations
  57. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A BOOTES-5 and 2.2m CAHA optical upper limits
  58. GRB 250129A: GRANDMA Continued Afterglow Detection
  59. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  60. GRB 250205A: 1.3m DFOT optical upper limit
  61. GRB 250206A: Tiled Swift observations
  62. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
  63. GRB 250207B: Swift-XRT observations
  64. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates
  65. GRB 250208A: Fermi GBM Final Real-time Localization
  66. LIGO/Virgo/KAGRA S250208ad: Identification of a GW compact binary merger candidate
  67. EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
  68. GRB 250207A: Enhanced Swift-XRT position
  69. CHIME/FRB source FRB 20250206A detected less than 1 minute after LIGO-Virgo-Kagra (LVK) S250206dm, however the probability of spatial coincidence is order 0.1%
  70. GRB 250129A: ABObservatory SLOAN r’ afterglow detection
  71. GRB 250207A: REM IR afterglow detection
  72. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits
  73. GRB 250207B: Tiled Swift observations
  74. IGO/Virgo/KAGRA S250206dm: Virtual Telescope Project upper limit for the Neutrino IceCube Candidate
  75. GRB 250207A: REM optical afterglow detection
  76. GRB 250207A: Swift/UVOT Detection
  77. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limit for the Neutrino IceCube Candidate
  78. LIGO/Virgo/KAGRA S250206dm: GOTO observations of optical candidates AT 2025azn and AT 2025azm
  79. LIGO/Virgo/KAGRA S250206dm: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  80. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the AT 2025azn Optical Candidate
  81. GRB 250129A: Continued AbAO and Mondy optical observations
  82. LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
  83. GRB 250207A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  84. GRB 250207A: Swift detection of a burst with optical counterpart
  85. LIGO/Virgo/KAGRA S250206dm: Identification of a GW compact binary merger candidate
  86. GRB 250205A: REM NIR upper limit
  87. GRB 250205A: Swift/UVOT Upper Limits
  88. EP250205a/GRB 250205A: Einstein Probe observation
  89. GRB 250127C: SVOM/GRM observation of a burst
  90. GRB 250204B: SVOM/GRM observation of a likely short burst
  91. GRB 250205A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  92. GRB 250205A: Redshift from OSIRIS+/GTC z = 3.55
  93. GRB250205A: SVOM/VT optical afterglow detection
  94. GRB 250205A: OHP/T193 optical counterpart candidate
  95. LIGO/Virgo/KAGRA S250205ee: Identification of a GW compact binary merger candidate
  96. GRB 250205A: SVOM detection of a burst
  97. Konus-Wind detection of GRB 250201A
  98. IPN triangulation of GRB 250201A
  99. Konus-Wind detection of GRB 250202B
  100. IPN triangulation of GRB 250202B

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