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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_MC170219_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.

Advanced Search Examples (click to copy):

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

10925 results found.

  1. GRB 260504B: SVOM/ECLAIRs refined analysis
  2. GRB 260504B: SVOM/VT optical upper limits
  3. GRB 260421B: radio observation with the VLA
  4. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  5. EP260416a: Mondy and Terskol optical upper limits
  6. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  7. GRB 260401A: cubesat Avion detection
  8. The EP-WXT trigger 01709258652: Mondy optical observations
  9. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  10. EP260416a: Mondy optical observations
  11. EP260416a: ZTSh R band observations
  12. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  13. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  14. GRB 260421B: SVOM/VT optical observations
  15. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  16. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  17. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  18. EP260416a: Optical follow-up observations with Kinder
  19. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  20. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  21. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  22. EP260416a: SVOM/VT optical observation
  23. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  24. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  25. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  26. EP260321a: CMO SAI J,K observations
  27. EP260321a: SVOM/VT optical observations and color changes around peak
  28. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  29. The EP-WXT trigger 01709260010 is likely a flaring star
  30. GRB 260411B: Fermi-LAT detection
  31. EP-WXT01709259790: Optical Upper limits with kinder observations
  32. EP260409a: SVOM/VT optical upper limits
  33. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  34. EP260321a: VLA radio detection
  35. EP260405a: GMOS-N optical upper limits
  36. EP260405a: SVOM/VT optical upper limits
  37. GRB 260330B: SVOM/VT further optical observation
  38. EP260403a: LCO optical observations of the counterpart
  39. GRB 260330B: SVOM/VT optical candidate
  40. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  41. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  42. GRB 260401A: MAXI/GSC detection
  43. EP260329b: Mondy and Assy-Turgen optical upper limits
  44. GRB 260330B: SVOM/VT optical upper limits
  45. EP260329b: Optical follow-up with Kinder observations
  46. EP260329a: Optical upper limit with Kinder observations
  47. EP260327a: SVOM/VT optical upper limits
  48. EP260327a: Gemini-North optical upper limits
  49. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  50. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  51. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  52. GRB 260310A: LBT optical observations
  53. EP260321A: Mondy optical observations
  54. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  55. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  56. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  57. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  58. EP260321a: further Kinder optical observations
  59. GRB 260321A: SVOM/VT optical upper limits
  60. EP260321a: SVOM/VT optical upper limit
  61. GRB 260310A: continued optical observation at Mondy
  62. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  63. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  64. GRB 260310A/AT2026fgk: LBT near-infrared observations
  65. GRB 260310A / AT 2026fgk: radio detection with the VLA
  66. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  67. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  68. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  69. EP260316a: optical upper limit with Kinder observations
  70. EP260314a: optical upper limit with Kinder observations
  71. EP260314a: SVOM/VT optical candidate
  72. GRB 260310A / AT2026fgk: SAO RAS optical observations
  73. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  74. GRB 260310A: NOT optical polarimetry
  75. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  76. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  77. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  78. GRB 260312A: Swift detection of a burst
  79. GRB 260131A/B: radio detection with the VLA
  80. EP260306a: Mondy optical upper limit
  81. GRB 260208A: radio detection with the VLA
  82. GRB 260307B: SVOM/VT upper limit with X band data analysis
  83. GRB 260307B: SVOM/VT optical candidate
  84. EP260302a: SVOM/VT optical observation
  85. EP260306a: Gemini-North redshift z = 4.773
  86. EP260306a: SVOM/VT optical observation
  87. EP260302a: Gemini-South redshift z = 1.535
  88. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  89. GRB 260303A: SVOM/VT optical observations
  90. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  91. EP260227a: Mondy optical observations
  92. EP260227a: SVOM/VT optical observation
  93. GRB 260228A: SVOM/VT optical upper limits
  94. EP260227A: 3.6m DOT optical afterglow detection
  95. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  96. EP260227a: Liverpool Telescope observations
  97. GRB 260225A: SVOM/VT optical continued observations and upper limit
  98. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  99. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  100. EP260214a: VLT/FORS2 optical observations

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