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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"

32495 results found.

  1. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  2. EP250215a / GRB 250215A : GTC redshift z = 4.61
  3. GRB 250215A: Fermi GBM Observation
  4. EP250215a / GRB 250215A : NOT optical observations
  5. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  6. GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
  7. LIGO/Virgo/KAGRA S250206dm: MASTER LC AT2025bbo
  8. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  9. GRB 250215A: Swift-XRT refined Analysis
  10. GRB 250215A: SVOM/GRM observation
  11. EP250215a / GRB 250215A: AstroSat CZTI detection
  12. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  13. EP250215a: Global MASTER-Net observations report
  14. EP250215A/GRB 250215A: INTEGRAL SPI-ACS detection
  15. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  16. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  17. Fermi GRB 250215A: Global MASTER-Net observations report
  18. GRB 250213A:SVOM/VT optical candidate
  19. EP250207b: Xinglong optical upper limit
  20. Fermi GRB 250214A: Global MASTER-Net observations report
  21. GRB 250213A: Swift ToO observations
  22. EP250212a: Xinglong optical upper limit
  23. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  24. EP250212a: Global MASTER-Net observations report
  25. GRB 250205A: VIRT Optical Upper Limit
  26. GRB 250205A: Leavitt Observatory optical upper limit
  27. GRB 250210A: GRBAlpha detection
  28. EP250207B: Chandra localization of the X-ray counterpart
  29. LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
  30. EP250207b: VLA radio upper limits
  31. EP250212a: Liverpool Telescope optical upper limits
  32. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  33. GRB250101A: Radio upper limits from GMRT observations
  34. EP250207B: GTC z-band Observations
  35. Fermi GRB 250212A: Global MASTER-Net observations report
  36. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  37. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  38. EP250207b: NOT optical counterpart candidate
  39. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  40. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  41. GRB 250211A: Swift ToO observations
  42. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  43. LIGO/Virgo/KAGRA S250211be: Updated Sky localization
  44. GRB 250207A: Fermi GBM Observation
  45. GRB 250206A: Fermi GBM Observation
  46. GRB 250205A / EP250205A: radio detection with the VLA
  47. IceCube-250207A: One candidate from the Zwicky Transient Facility
  48. EP250207b: Tentative z-band brightening source
  49. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  50. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  51. Konus-Wind detection of GRB 250207A
  52. Konus-Wind detection of GRB 250206A
  53. GRB 250210A: SVOM/GRM observation of a long burst
  54. EP250207b: Liverpool Telescope possible optical counterpart
  55. EP250207b: Global MASTER-Net observations report
  56. Gemini-South spectroscopic redshift of EP250207b host galaxy candidate (z=0.082)
  57. LIGO/Virgo/KAGRA S250211be: Identification of a GW compact binary merger candidate
  58. LIGO/Virgo/KAGRA S250211aa: Updated Sky localization and EM Bright Classification
  59. LIGO/Virgo/KAGRA S250211aa: Identification of a GW compact binary merger candidate
  60. GRB 250207A: Skynet optical afterglow observations
  61. LIGO/VIRGO/KAGRA S250206dm: AT 2025bbo spectroscopic observations with NIRES on Keck II
  62. LIGO/Virgo/KAGRA S250206dm: Gemini-North spectroscopic observation of AT2025bbo and its host galaxy
  63. GRB 241128A: VIRT Optical Upper Limit
  64. EP250207b: Gemini GMOS-N z-band observations
  65. EP250207A: Upper limits from Fermi-GBM Observations
  66. GRB 250210A: INTEGRAL SPI-ACS detection
  67. GRB 250210A: AstroSat CZTI detection
  68. LIGO/Virgo/KAGRA S250206dm: MASTER detection AT2025bbo
  69. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  70. Fermi GRB 250210A: Global MASTER-Net observations report
  71. LIGO/Virgo/KAGRA S250206dm: Upper limits from GECAM Observations
  72. IceCube-250207A: Upper limits from a search for additional neutrino events in IceCube
  73. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  74. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  75. GRB 250204B: GRBAlpha detection
  76. GRB 250204A: GRBAlpha detection
  77. LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: MASTER observations and possible mother galaxy
  78. LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
  79. Fermi-LAT Gamma-ray Observations of IceCube-250207A
  80. GRB 250207A: 1.3m DFOT Optical observations
  81. LIGO/Virgo/KAGRA S250206dm: WFST follow-up observations
  82. GRB 250129A: GRANDMA Continued Afterglow Detection
  83. GRB 250207A: Swift-BAT refined analysis
  84. LIGO/Virgo/KAGRA S250206dm: further Pan-STARRS observations and one candidate AT2025bbo
  85. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  86. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  87. GRB 250205A: 1.3m DFOT optical upper limit
  88. GRB 250206A: Tiled Swift observations
  89. LIGO/Virgo/KAGRA S250118az: Updated Sky localization
  90. LIGO/Virgo/KAGRA S250208ad: Updated Sky localization
  91. GRB 250206A: EIRSAT-1 GMOD Detection
  92. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
  93. GRB 250206A: Fermi-LAT detection
  94. LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
  95. IceCube-250203A: No transient candidates from the Zwicky Transient Facility
  96. LIGO/Virgo/KAGRA S250206dm: Spectroscopic Classification of AT2025bay and AT2025baz with Keck I/LRIS
  97. LIGO/Virgo/KAGRA S250206dm: Candidates from the Zwicky Transient Facility
  98. LIGO/Virgo/KAGRA S250206dm: ePESSTO+ classification of AT2025bar
  99. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates
  100. LIGO/Virgo/KAGRA S250208ad: Identification of a GW compact binary merger candidate

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