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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"
  1. EP250207a: EP-WXT detection and XRT follow-up observation
  2. LIGO/Virgo/KAGRA S250208ad: Identification of a GW compact binary merger candidate
  3. LIGO/Virgo/KAGRA S250206dm: MMT galaxy targeted observations
  4. GRB 250207A: Swift-XRT refined Analysis
  5. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A & "Time Machine" Effect.
  6. EP-WXT trigger 01709131361: correction to GCN 39214
  7. EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
  8. GRB 250207A: Enhanced Swift-XRT position
  9. 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%
  10. LIGO/Virgo/KAGRA S250206dm: GOTO counterpart search update - AT2025bar
  11. EP-WXT trigger 01709131361 / LIGO/Virgo/KAGRA S250206dm: FTW optical and NIR observations
  12. GRB 250129A: ABObservatory SLOAN r’ afterglow detection
  13. GRB 250207A: REM IR afterglow detection
  14. LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap
  15. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS survey of the skymap for optical transients
  16. GRB 250207A: FRAM-Auger optical detection
  17. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits
  18. GRB 250207B: Tiled Swift observations
  19. LIGO/Virgo/KAGRA S250207bg: NED Galaxies in the Localization Volume
  20. Konus-Wind detection of GRB 250204B
  21. IGO/Virgo/KAGRA S250206dm: Virtual Telescope Project upper limit for the Neutrino IceCube Candidate
  22. IceCube-250207A - IceCube observation of a high-energy neutrino candidate track-like event
  23. GRB 250207A: REM optical afterglow detection
  24. LIGO/Virgo/KAGRA S250207bg: Identification of a GW compact binary merger candidate
  25. LIGO/Virgo/KAGRA S250206dm:GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  26. GRB 250207A: Swift/UVOT Detection
  27. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limit for the Neutrino IceCube Candidate
  28. LIGO/Virgo/KAGRA S250206dm: GOTO observations of optical candidates AT 2025azn and AT 2025azm
  29. LIGO/Virgo/KAGRA S250206dm: SOAR galaxy targeted observations
  30. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS observations of AT2025azm and AT2025azn
  31. LIGO/Virgo/KAGRA S250206dm: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  32. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the AT 2025azn Optical Candidate
  33. GRB 250129A: Continued AbAO and Mondy optical observations
  34. LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
  35. GRB 250207B: MAXI/GSC detection
  36. The EP-WXT trigger 01709131347 is likely a flaring star
  37. The EP-WXT trigger 01709131332 is likely a flaring star
  38. The EP-WXT trigger 01709131290 is likely a flaring star
  39. GRB 250207A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  40. LIGO/Virgo/KAGRA S250206dm: Updated-6 NED Galaxies in the Localization Volume
  41. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  42. LIGO/Virgo/KAGRA S250206dm: Upper limits from Fermi-GBM Observations
  43. GRB 250207A: Swift detection of a burst with optical counterpart
  44. GRB 250207A: Fermi GBM Final Real-time Localization
  45. Fermi-LAT Gamma-ray Observations of IceCube-250203A
  46. LIGO/Virgo/KAGRA S250206dm: Coverage and upper limits from MAXI/GSC observations
  47. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  48. LIGO/Virgo/KAGRA S250206dm: Updated NED Galaxies in the Localization Volume
  49. LIGO/Virgo/KAGRA S250206dm: Two counterpart neutrino candidates from IceCube neutrino searches
  50. LIGO/Virgo/KAGRA S250206dm: Identification of a GW compact binary merger candidate
  51. LIGO/Virgo/KAGRA S250206dm: NED Galaxies in the Localization Volume
  52. GRB 250206A: BALROG localization (Fermi Trigger 760564296 / GRB 250206827)
  53. GRB 250206A: Fermi GBM Final Real-time Localization
  54. GRB 250205A: Fermi GBM Observation
  55. GRB 250205A: REM NIR upper limit
  56. EP250205a/GRB 250205A: FTW optical and NIR observations of the counterpart
  57. GRB 250205A: Swift/UVOT Upper Limits
  58. LIGO/Virgo/KAGRA S250205ee: Updated Sky localization and Source Classification
  59. EP250205a/GRB 250205A: correction to the source localization
  60. EP250205a/GRB 250205A: Einstein Probe observation
  61. GRB 250127C: SVOM/GRM observation of a burst
  62. GRB 250204B: SVOM/GRM observation of a likely short burst
  63. GRB 250205A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  64. GRB 250205A: Swift/XRT detection
  65. GRB 250205A: Redshift from OSIRIS+/GTC z = 3.55
  66. GRB250205A: SVOM/VT optical afterglow detection
  67. GRB 250205A: GOTO optical upper limits
  68. GRB 250205A: OHP/T193 optical counterpart candidate
  69. GRB 250205A: Liverpool Telescope optical counterpart candidate detection
  70. LIGO/Virgo/KAGRA S250205ee: Identification of a GW compact binary merger candidate
  71. GRB 250205A: SVOM detection of a burst
  72. LIGO/Virgo/KAGRA S250205bk: NED Galaxies in the Localization Volume
  73. Konus-Wind detection of GRB 250201A
  74. IPN triangulation of GRB 250201A
  75. LIGO/Virgo/KAGRA S250205bk: Updated Sky localization
  76. Konus-Wind detection of GRB 250202B
  77. LIGO/Virgo/KAGRA S250205bk: Identification of a GW compact binary merger candidate
  78. GRB 250129A: Swift-BAT refined analysis
  79. EP 250108A: Upper limits from Fermi-GBM Observations
  80. IPN triangulation of GRB 250204B (short/hard)
  81. IPN triangulation of GRB 250202B
  82. LIGO/Virgo/KAGRA S250204ax: Updated Sky localization
  83. GRB 250204B: AstroSat CZTI detection of a short burst
  84. GRB 250204B: Fermi GBM Final Localization
  85. GRB 250129A: LCO late afterglow detection
  86. GRB 250129A: AbAO AS-32 and Mondy AZT-33IK optical observations
  87. GRB 250204A: Fermi GBM Final Real-time Localization
  88. LIGO/Virgo/KAGRA S250204ax: Identification of a GW compact binary merger candidate
  89. GRB 250129A: COLIBRÍ/DDRAGO Afterglow Detection
  90. GRB 250202B: NuSTAR detection of the prompt emission
  91. GRB 250202C: GRBAlpha detection
  92. GRB 250202B: Fermi GBM Detection
  93. IceCube-250203A - IceCube observation of a high-energy neutrino candidate track-like event
  94. GRB 250129a: Liverpool Telescope optical follow-up
  95. GRB 240129A: further SAO RAS optical observations
  96. GRB 250129A: 7DT Detection and Medium-band SED of Afterglow
  97. LIGO/Virgo/KAGRA S250202cu: Updated Sky localization
  98. The EP-WXT trigger 01709131196 is likely a flaring star
  99. GRB 250202C: Fermi GBM Final Real-time Localization
  100. LIGO/Virgo/KAGRA S250202cu: Identification of a GW compact binary merger candidate

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