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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.

"N/A_MC161202_R1" does not adhere to advanced search syntax. Please refer to the documentation and try again.
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.

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

10918 results found.

  1. The EP-WXT trigger 01709258652: Mondy optical observations
  2. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  3. EP260416a: Mondy optical observations
  4. EP260416a: ZTSh R band observations
  5. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  6. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  7. GRB 260421B: SVOM/VT optical observations
  8. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  9. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  10. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  11. EP260416a: Optical follow-up observations with Kinder
  12. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  13. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  14. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  15. EP260416a: SVOM/VT optical observation
  16. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  17. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  18. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  19. EP260321a: CMO SAI J,K observations
  20. EP260321a: SVOM/VT optical observations and color changes around peak
  21. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  22. The EP-WXT trigger 01709260010 is likely a flaring star
  23. GRB 260411B: Fermi-LAT detection
  24. EP-WXT01709259790: Optical Upper limits with kinder observations
  25. EP260409a: SVOM/VT optical upper limits
  26. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  27. EP260321a: VLA radio detection
  28. EP260405a: GMOS-N optical upper limits
  29. EP260405a: SVOM/VT optical upper limits
  30. GRB 260330B: SVOM/VT further optical observation
  31. EP260403a: LCO optical observations of the counterpart
  32. GRB 260330B: SVOM/VT optical candidate
  33. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  34. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  35. GRB 260401A: MAXI/GSC detection
  36. EP260329b: Mondy and Assy-Turgen optical upper limits
  37. GRB 260330B: SVOM/VT optical upper limits
  38. EP260329b: Optical follow-up with Kinder observations
  39. EP260329a: Optical upper limit with Kinder observations
  40. EP260327a: SVOM/VT optical upper limits
  41. EP260327a: Gemini-North optical upper limits
  42. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  43. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  44. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  45. GRB 260310A: LBT optical observations
  46. EP260321A: Mondy optical observations
  47. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  48. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  49. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  50. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  51. EP260321a: further Kinder optical observations
  52. GRB 260321A: SVOM/VT optical upper limits
  53. EP260321a: SVOM/VT optical upper limit
  54. GRB 260310A: continued optical observation at Mondy
  55. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  56. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  57. GRB 260310A/AT2026fgk: LBT near-infrared observations
  58. GRB 260310A / AT 2026fgk: radio detection with the VLA
  59. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  60. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  61. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  62. EP260316a: optical upper limit with Kinder observations
  63. EP260314a: optical upper limit with Kinder observations
  64. EP260314a: SVOM/VT optical candidate
  65. GRB 260310A / AT2026fgk: SAO RAS optical observations
  66. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  67. GRB 260310A: NOT optical polarimetry
  68. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  69. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  70. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  71. GRB 260312A: Swift detection of a burst
  72. GRB 260131A/B: radio detection with the VLA
  73. EP260306a: Mondy optical upper limit
  74. GRB 260208A: radio detection with the VLA
  75. GRB 260307B: SVOM/VT upper limit with X band data analysis
  76. GRB 260307B: SVOM/VT optical candidate
  77. EP260302a: SVOM/VT optical observation
  78. EP260306a: Gemini-North redshift z = 4.773
  79. EP260306a: SVOM/VT optical observation
  80. EP260302a: Gemini-South redshift z = 1.535
  81. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  82. GRB 260303A: SVOM/VT optical observations
  83. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  84. EP260227a: Mondy optical observations
  85. EP260227a: SVOM/VT optical observation
  86. GRB 260228A: SVOM/VT optical upper limits
  87. EP260227A: 3.6m DOT optical afterglow detection
  88. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  89. EP260227a: Liverpool Telescope observations
  90. GRB 260225A: SVOM/VT optical continued observations and upper limit
  91. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  92. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  93. EP260214a: VLT/FORS2 optical observations
  94. GRB 260226A: CALET Gamma-Ray Burst Monitor detection
  95. EP260214a: VLA 6 GHz detection
  96. GRB 260225A: SVOM/VT optical observation
  97. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  98. GRB 260225A: SVOM/VT optical upper limits
  99. EP260126a: VLA 6 GHz detection
  100. EP260223a: Liverpool Telescope upper limits

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