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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"

16156 results found.

  1. GRB 251201B: SALT spectroscopic redshift z = 1.599
  2. GRB 251203C: J-band observations with WINTER
  3. EP251130a: JinShan near-infrared observations
  4. GRB 251203C: LCO optical afterglow confirmation
  5. GRB 251203C: SVOM/VT optical counterpart
  6. GRB 251203C: LCO optical upper limits
  7. GRB 251203B: LCO optical upper limits
  8. GRB 251203B: SVOM/VT optical observation
  9. GRB 251202A / EP251202a: Liverpool Telescope optical follow-up observations
  10. GRB 251129A / EP251129a: SVOM/VT optical color bluer
  11. EP251130a: MAO/AZT-22 optical observations
  12. GRB 251202A / EP251202a: SVOM/VT optical observation
  13. EP251202a/GRB 251202A: KAIT optical observations
  14. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  15. GRB251129A/EP251129a: Swift UVOT detection
  16. GRB 251201B: Kilonova-Catcher optical afterglow detection
  17. EP251130a: continued NOT optical observations indicate steep fading phase
  18. GRB 251122A/EP251122a: CrAO ZTSh optical observations
  19. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  20. GRB 251202A: GOTO optical afterglow detection
  21. GRB 251126A: SAO RAS optical marginal detection
  22. GRB 251202A: Swift-XRT afterglow detection
  23. EP251129a/GRB 251129A: NOWT Detection
  24. GRB 251126A: SVOM/VT optical observation
  25. EP251130a: SVOM/VT optical observation
  26. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  27. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  28. EP251202a/trigger 01709249064: Las Cumbres discovery of the optical counterpart
  29. GRB 251201A: SVOM/GRM observation of a burst
  30. GRB 251201B: SVOM/VT optical fading
  31. Swift GRB 251201B : MASTER optical counterpart detection
  32. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  33. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  34. GRB 251201B: Swift detection of a burst with an optical counterpart
  35. EP251130a: Mondy optical observations
  36. EP251130a: Optical detections with Kinder observations
  37. EP251130a: SAO RAS optical observations
  38. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  39. EP251130a: KAIT optical observations
  40. EP251130A: Optical observation from 1.3m DFOT
  41. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  42. EP251130a: JinShan optical observations
  43. GRB 251127A: SVOM/GRM observation
  44. EP251130a: Swift-XRT counterpart detection
  45. EP251130a: COLIBRÍ optical counterpart candidate
  46. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  47. GRB 251129A / EP251129a: OSN and CAHA optical follow-up
  48. GRB 251129A / EP251129a: SAO RAS optical observations
  49. GRB 251126A: SAO RAS optical observations
  50. GRB 251128A: SVOM/GRM observation of a long burst
  51. SVOM GRB 251129A : MASTER optical counterpart detection
  52. GRB 251129A: Swift-XRT afterglow detection
  53. GRB 251129A / EP251129a: SVOM/VT optical fading
  54. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  55. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  56. GRB 251129A: Correction to the position of the optical counterpar
  57. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  58. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  59. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  60. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  61. GRB 251126A: further SAO RAS optical observations
  62. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  63. GRB 251126A NUTTelA-TAO Early Measurements
  64. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  65. GRB251126A: MAO/AZT-22 optical observations
  66. GRB251126A: Continued optical observation from 1.3m DFOT
  67. GRB 251126A: Swift/UVOT Detection
  68. EP251124a: Pan-STARRS ri-band imaging and photometry
  69. GRB 251126A: Mondy and SAO RAS optical observations
  70. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  71. GRB 251126A: NOT optical observations
  72. GRB 251126A: 1.3m DFOT optical afterglow detection
  73. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  74. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  75. GRB 251126A: Kilonova-Catcher optical afterglow detection
  76. GRB 251126A: Asiago i-band detection
  77. GRB 251126A: Nanshan/HMT optical afterglow detection
  78. GRB 251126A: GIT discovery of the likely optical afterglow
  79. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  80. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  81. EP251124b: NOT r- and z-band optical upper limits
  82. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  83. EP251124a: Xinglong GWAC-F60A optical observation
  84. EP251124a: NOT r- and z-band optical upper limits
  85. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  86. EP251124a: Optical upper limit with Kinder observations
  87. EP251118A: 6 GHz VLA Detection
  88. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  89. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  90. EP251124a: GROWTH-India Telescope optical upper limits
  91. GRB 251122A/EP251122a: FTW optical and NIR observations
  92. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  93. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  94. EP251118A: 3.6m DOT optical afterglow detection
  95. GRB 251122A / EP251122a: EP-FXT counterpart detection
  96. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  97. GRB 251122A / EP251122a: WFST optical observations
  98. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  99. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  100. GRB 251122A / EP251122a: LCO optical upper limits

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