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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').
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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.

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subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

32485 results found.

  1. EP250215a / GRB 250215A: AstroSat CZTI detection
  2. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  3. EP250215a: Global MASTER-Net observations report
  4. EP250215A/GRB 250215A: INTEGRAL SPI-ACS detection
  5. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  6. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  7. Fermi GRB 250215A: Global MASTER-Net observations report
  8. GRB 250213A:SVOM/VT optical candidate
  9. EP250207b: Xinglong optical upper limit
  10. Fermi GRB 250214A: Global MASTER-Net observations report
  11. GRB 250213A: Swift ToO observations
  12. EP250212a: Xinglong optical upper limit
  13. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  14. EP250212a: Global MASTER-Net observations report
  15. GRB 250205A: VIRT Optical Upper Limit
  16. GRB 250205A: Leavitt Observatory optical upper limit
  17. GRB 250210A: GRBAlpha detection
  18. EP250207B: Chandra localization of the X-ray counterpart
  19. LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
  20. EP250207b: VLA radio upper limits
  21. EP250212a: Liverpool Telescope optical upper limits
  22. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  23. GRB250101A: Radio upper limits from GMRT observations
  24. EP250207B: GTC z-band Observations
  25. Fermi GRB 250212A: Global MASTER-Net observations report
  26. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  27. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  28. EP250207b: NOT optical counterpart candidate
  29. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  30. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  31. GRB 250211A: Swift ToO observations
  32. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  33. LIGO/Virgo/KAGRA S250211be: Updated Sky localization
  34. GRB 250207A: Fermi GBM Observation
  35. GRB 250206A: Fermi GBM Observation
  36. GRB 250205A / EP250205A: radio detection with the VLA
  37. IceCube-250207A: One candidate from the Zwicky Transient Facility
  38. EP250207b: Tentative z-band brightening source
  39. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  40. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  41. Konus-Wind detection of GRB 250207A
  42. Konus-Wind detection of GRB 250206A
  43. GRB 250210A: SVOM/GRM observation of a long burst
  44. EP250207b: Liverpool Telescope possible optical counterpart
  45. EP250207b: Global MASTER-Net observations report
  46. Gemini-South spectroscopic redshift of EP250207b host galaxy candidate (z=0.082)
  47. LIGO/Virgo/KAGRA S250211be: Identification of a GW compact binary merger candidate
  48. LIGO/Virgo/KAGRA S250211aa: Updated Sky localization and EM Bright Classification
  49. LIGO/Virgo/KAGRA S250211aa: Identification of a GW compact binary merger candidate
  50. GRB 250207A: Skynet optical afterglow observations
  51. LIGO/VIRGO/KAGRA S250206dm: AT 2025bbo spectroscopic observations with NIRES on Keck II
  52. LIGO/Virgo/KAGRA S250206dm: Gemini-North spectroscopic observation of AT2025bbo and its host galaxy
  53. GRB 241128A: VIRT Optical Upper Limit
  54. EP250207b: Gemini GMOS-N z-band observations
  55. EP250207A: Upper limits from Fermi-GBM Observations
  56. GRB 250210A: INTEGRAL SPI-ACS detection
  57. GRB 250210A: AstroSat CZTI detection
  58. LIGO/Virgo/KAGRA S250206dm: MASTER detection AT2025bbo
  59. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  60. Fermi GRB 250210A: Global MASTER-Net observations report
  61. LIGO/Virgo/KAGRA S250206dm: Upper limits from GECAM Observations
  62. IceCube-250207A: Upper limits from a search for additional neutrino events in IceCube
  63. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  64. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  65. GRB 250204B: GRBAlpha detection
  66. GRB 250204A: GRBAlpha detection
  67. LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: MASTER observations and possible mother galaxy
  68. LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
  69. Fermi-LAT Gamma-ray Observations of IceCube-250207A
  70. GRB 250207A: 1.3m DFOT Optical observations
  71. LIGO/Virgo/KAGRA S250206dm: WFST follow-up observations
  72. GRB 250129A: GRANDMA Continued Afterglow Detection
  73. GRB 250207A: Swift-BAT refined analysis
  74. LIGO/Virgo/KAGRA S250206dm: further Pan-STARRS observations and one candidate AT2025bbo
  75. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  76. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  77. GRB 250205A: 1.3m DFOT optical upper limit
  78. GRB 250206A: Tiled Swift observations
  79. LIGO/Virgo/KAGRA S250118az: Updated Sky localization
  80. LIGO/Virgo/KAGRA S250208ad: Updated Sky localization
  81. GRB 250206A: EIRSAT-1 GMOD Detection
  82. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
  83. GRB 250206A: Fermi-LAT detection
  84. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  85. IceCube-250203A: No transient candidates from the Zwicky Transient Facility
  86. LIGO/Virgo/KAGRA S250206dm: Spectroscopic Classification of AT2025bay and AT2025baz with Keck I/LRIS
  87. LIGO/Virgo/KAGRA S250206dm: Candidates from the Zwicky Transient Facility
  88. LIGO/Virgo/KAGRA S250206dm: ePESSTO+ classification of AT2025bar
  89. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates
  90. LIGO/Virgo/KAGRA S250208ad: Identification of a GW compact binary merger candidate
  91. LIGO/Virgo/KAGRA S250206dm: MMT galaxy targeted observations
  92. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A & "Time Machine" Effect.
  93. EP-WXT trigger 01709131361: correction to GCN 39214
  94. EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
  95. 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%
  96. LIGO/Virgo/KAGRA S250206dm: GOTO counterpart search update - AT2025bar
  97. EP-WXT trigger 01709131361 / LIGO/Virgo/KAGRA S250206dm: FTW optical and NIR observations
  98. GRB 250129A: ABObservatory SLOAN r’ afterglow detection
  99. GRB 250207A: REM IR afterglow detection
  100. LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap

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