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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').
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"

20966 results found.

  1. GRB 250205A: OHP/T193 optical counterpart candidate
  2. GRB 250205A: Liverpool Telescope optical counterpart candidate detection
  3. LIGO/Virgo/KAGRA S250205bk: NED Galaxies in the Localization Volume
  4. EP 250108A: Upper limits from Fermi-GBM Observations
  5. GRB 250129A: LCO late afterglow detection
  6. GRB 250129A: AbAO AS-32 and Mondy AZT-33IK optical observations
  7. GRB 250129A: COLIBRÍ/DDRAGO Afterglow Detection
  8. GRB 250129a: Liverpool Telescope optical follow-up
  9. GRB 240129A: further SAO RAS optical observations
  10. GRB 250129A: 7DT Detection and Medium-band SED of Afterglow
  11. GRB 250129A: SVOM/C-GFT optical observations
  12. Swift GRB250129A: MASTER 4 days observations report
  13. GRB 250201A: INTEGRAL SPI/ACS detection
  14. GRB 250129A: 1.3m DFOT Optical observations
  15. GRB 250129A: Liverpool Telescope observations suggest continued engine activity
  16. LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations
  17. GRB 250129A: Skynet Continued Optical Observations
  18. GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
  19. GRB 250129A: SAO RAS optical observations
  20. GRB 250129A: COLIBRÍ Continuing Detection of the Afterglow
  21. GRB 250129A: optical photometry from Konkoly
  22. GRB 250129A: COLIBRÍ Optical Observations
  23. GRB 250128B: VLA possible radio detection
  24. GRB 250129A: continued KAIT observations indicating steep decay after 28.5h
  25. GRB 250129A: NOT optical observations of continuining activity
  26. GRB 250129a: Liverpool Telescope optical follow-up
  27. GRB 250129A: AKO Optical Afterglow Detection
  28. GRB 250129A: GRANDMA/TAROT optical afterglow detection
  29. GRB 250128B: SAO RAS Zeiss-1000 and CrAO ZTSh optical upper limits
  30. GRB 250128B: VLA radio upper limit
  31. Ep250125A: 1.3m DFOT optical upper limit
  32. GRB 250129A: Skynet optical observations
  33. GRB 250129A: KAIT optical observations of the rebrightening around 5.1 hours
  34. GRB 250128B: Gemini-North optical extended source detection
  35. The EP-WXT trigger 01709131085: KAIT confirmation of the stellar flare
  36. GRB 250129A: Swift/UVOT Detection
  37. GRB 250128B: VLT/HAWKI near-infrared observations
  38. GRB 250127A: CrAO and Terskol optical upper limits
  39. GRB 250128B: VLT/FORS2 optical observations
  40. GRB 250129A: REM optical/NIR afterglow detection
  41. GRB 250129A: OHP/T193 optical and spectroscopy observations
  42. GRB 250129A: Early afterglow detection by LCO.
  43. Swift GRB 250129A: Global MASTER-Net Slowly evolving LC detection
  44. GRB 250129A: LCO optical observations
  45. GRB 250129A: NOT optical observations and redshift confirmation
  46. GRB 250129A: GOTO optical observations show brightening afterglow
  47. GRB 250129A: VLT/X-shooter redshift of z = 2.151
  48. Swift GRB 250129A: Global MASTER-Net observations report
  49. Fermi GRB 250128B: Global MASTER-Net observations report
  50. GRB 250128B: GOTO optical upper limit
  51. Swift GRB 250128B: Global MASTER-Net observations report
  52. GRB 250128B: LCO optical observations
  53. GRB 250127A: Swift-XRT observations
  54. GRB 250127B: DDOTI Upper Limit on the Afterglow
  55. Fermi-LAT Gamma-ray Observations of IceCube-250102A
  56. Fermi GRB 250128A: Global MASTER-Net observations report
  57. Fermi GRB 250127B: Global MASTER-Net observations report
  58. Fermi-LAT Gamma-ray Observations of IceCube-250101A
  59. GRB 250127A: SVOM/VT upper limit
  60. GRB 250127A: Swift ToO observations
  61. GRB 250127A: LCO optical upper limit
  62. EP250125A: Non-detection from Fermi-GBM Observations
  63. EP250125a: Optical upper limit with Kinder observations
  64. EP250125a: REM optical counterpart detection
  65. EP250125a: Swift/XRT detection of a fading counterpart
  66. EP250125a: a new X-ray transient detected by Einstein Probe
  67. EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
  68. EP250108a: AbAO, CMO and Terskol optical upper limits
  69. GRB 250121A: INTEGRAL/SPI-ACS detection
  70. LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
  71. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  72. EP250108a/AT2025kg: 1.3m DFOT Optical observations
  73. ATCA detection of possible radio counterpart to GRB 250114A
  74. EP250108a / SN2025kg: Non-detection from ATCA radio follow-up observations
  75. GRB 250119B: INTEGRAL/SPI-ACS detection
  76. EP 250108A: Late-time optical observation by LCO
  77. LIGO/Virgo/KAGRA S250119cv: Updated NED Galaxies in the Localization Volume
  78. LIGO/Virgo/KAGRA S250119cv: NED Galaxies in the Localization Volume
  79. EP250108a / SN2025kg: Gemini GMOS-S confirmation of an associated broad-lined SN Ic
  80. EP250108a/AT 2025kg: NOT spectroscopy in agreement with SN Ic-BL
  81. EP250108a / AT 2025kg: the kangaroo is hopping, evidence for optical rebrightening
  82. GRB 250117A: GECAM observation of a short burst
  83. EP250108a / AT2025kg: GMG Optical Observations
  84. EP250108a / AT2025kg: VLA radio upper limit
  85. GRB 241217A / EP241217B: radio detection with the VLA
  86. GRB 250116A: INTEGRAL/SPI-ACS and PICsIT detection
  87. GRB 250114B: Swift-XRT afterglow detection
  88. GRB 250114B: SVOM/VT upper limit
  89. EP250108a: MeerKAT radio upper limit
  90. LIGO/Virgo/KAGRA S250114ax: Updated NED Galaxies in the Localization Volume
  91. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  92. GRB 250114B: Liverpool Telescope optical upper limit
  93. GRB 250114B : MITSuME Akeno optical afterglow candidate detection
  94. GRB 250114B: Swift-XRT observations
  95. GRB 250114A: LCO optical counterpart detection.
  96. GRB 250114A: GRANDMA/TAROT optical afterglow detection
  97. Integral GRB250114.55: Global MASTER-Net observations report
  98. GRB 250114A: LCOGT optical afterglow i-band detection
  99. GRB 250114B: Swift ToO observations
  100. LIGO/Virgo/KAGRA S250114ax: NED Galaxies in the Localization Volume

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