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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.

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

16160 results found.

  1. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS survey of the skymap for optical transients
  2. GRB 250207A: FRAM-Auger optical detection
  3. IGO/Virgo/KAGRA S250206dm: Virtual Telescope Project upper limit for the Neutrino IceCube Candidate
  4. GRB 250207A: REM optical afterglow detection
  5. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limit for the Neutrino IceCube Candidate
  6. LIGO/Virgo/KAGRA S250206dm: GOTO observations of optical candidates AT 2025azn and AT 2025azm
  7. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS observations of AT2025azm and AT2025azn
  8. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the AT 2025azn Optical Candidate
  9. GRB 250129A: Continued AbAO and Mondy optical observations
  10. LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
  11. GRB 250207A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  12. GRB 250207A: Swift detection of a burst with optical counterpart
  13. GRB 250205A: REM NIR upper limit
  14. EP250205a/GRB 250205A: FTW optical and NIR observations of the counterpart
  15. GRB 250127C: SVOM/GRM observation of a burst
  16. GRB 250204B: SVOM/GRM observation of a likely short burst
  17. GRB 250205A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  18. GRB 250205A: Swift/XRT detection
  19. GRB 250205A: Redshift from OSIRIS+/GTC z = 3.55
  20. GRB250205A: SVOM/VT optical afterglow detection
  21. GRB 250205A: GOTO optical upper limits
  22. GRB 250205A: OHP/T193 optical counterpart candidate
  23. GRB 250205A: Liverpool Telescope optical counterpart candidate detection
  24. GRB 250205A: SVOM detection of a burst
  25. GRB 250129A: LCO late afterglow detection
  26. GRB 250129A: AbAO AS-32 and Mondy AZT-33IK optical observations
  27. GRB 250129a: Liverpool Telescope optical follow-up
  28. GRB 240129A: further SAO RAS optical observations
  29. GRB 250129A: 7DT Detection and Medium-band SED of Afterglow
  30. GRB 250129A: SVOM/C-GFT optical observations
  31. Swift GRB250129A: MASTER 4 days observations report
  32. GRB 250129A: 1.3m DFOT Optical observations
  33. GRB 250129A: Liverpool Telescope observations suggest continued engine activity
  34. GRB 250129A: Skynet Continued Optical Observations
  35. GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
  36. GRB 250129A: SAO RAS optical observations
  37. GRB 250129A: COLIBRÍ Continuing Detection of the Afterglow
  38. GRB 250129A: optical photometry from Konkoly
  39. GRB 250129A: COLIBRÍ Optical Observations
  40. GRB 250128B: VLA possible radio detection
  41. GRB 250129A: continued KAIT observations indicating steep decay after 28.5h
  42. GRB 250129A: iTelescope optical observation
  43. GRB 250129A: NOT optical observations of continuining activity
  44. GRB 250129a: Liverpool Telescope optical follow-up
  45. GRB 250129A: AKO Optical Afterglow Detection
  46. GRB 250129A: GRANDMA/TAROT optical afterglow detection
  47. GRB 250128B: SAO RAS Zeiss-1000 and CrAO ZTSh optical upper limits
  48. Ep250125A: 1.3m DFOT optical upper limit
  49. GRB 250129A: Skynet optical observations
  50. GRB 250129A: KAIT optical observations of the rebrightening around 5.1 hours
  51. GRB 250128B: Gemini-North optical extended source detection
  52. GRB 250128B: TNG optical upper limit
  53. GRB 250129A: Swift/UVOT Detection
  54. GRB 250127A: CrAO and Terskol optical upper limits
  55. GRB 250128B: NOT optical upper limit
  56. GRB 250128B: VLT/FORS2 optical observations
  57. GRB 250129A: REM optical/NIR afterglow detection
  58. GRB 250129A: OHP/T193 optical and spectroscopy observations
  59. GRB 250129A: Early afterglow detection by LCO.
  60. GRB 250128B: OHP/T193 optical upper limit
  61. Swift GRB 250129A: Global MASTER-Net Slowly evolving LC detection
  62. GRB 250129A: LCO optical observations
  63. GRB 250129A: NOT optical observations and redshift confirmation
  64. GRB 250129A: GOTO optical observations show brightening afterglow
  65. GRB 250129A: VLT/X-shooter redshift of z = 2.151
  66. GRB 250129A: Swift detection of a burst with an optical counterpart
  67. Swift GRB 250129A: Global MASTER-Net OT detection
  68. GRB 250128B: GOTO optical upper limit
  69. GRB 250128B: LCO optical observations
  70. GRB 250127A: LCO optical upper limit
  71. EP250125a: Optical upper limit with Kinder observations
  72. EP250125a: REM optical counterpart detection
  73. EP250125a: Swift/XRT detection of a fading counterpart
  74. EP250125a: a new X-ray transient detected by Einstein Probe
  75. EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
  76. EP250108a: AbAO, CMO and Terskol optical upper limits
  77. EP250108a/AT2025kg: 1.3m DFOT Optical observations
  78. EP250108a / SN2025kg: Non-detection from ATCA radio follow-up observations
  79. EP 250108A: Late-time optical observation by LCO
  80. EP250108a / SN2025kg: Gemini GMOS-S confirmation of an associated broad-lined SN Ic
  81. EP250108a/AT 2025kg: NOT spectroscopy in agreement with SN Ic-BL
  82. EP250108a / AT 2025kg: the kangaroo is hopping, evidence for optical rebrightening
  83. EP250108a / AT2025kg: GMG Optical Observations
  84. EP250108a / AT2025kg: VLA radio upper limit
  85. GRB 241217A / EP241217B: radio detection with the VLA
  86. GRB 250114B: Swift-XRT afterglow detection
  87. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  88. GRB 250114B: Liverpool Telescope optical upper limit
  89. GRB 250114B : MITSuME Akeno optical afterglow candidate detection
  90. GRB 250114A: LCO optical counterpart detection.
  91. GRB 250114B: OHP/T193 optical upper limit
  92. GRB 250114A: GRANDMA/TAROT optical afterglow detection
  93. GRB 250114A: LCOGT optical afterglow i-band detection
  94. GRB 250114B : GIT optical upper limit
  95. EP250111a: SAO RAS optical upper limit
  96. GRB 250114A: VLT/X-shooter spectroscopic redshift z = 4.732
  97. GRB 250114A: REM detection of the optical and NIR counterpart
  98. Swift GRB250114A: Global MASTER-Net OT detection
  99. GRB 250114A: LCO optical observations
  100. GRB 250114A: TRT optical observations

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