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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"

32489 results found.

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

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