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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').
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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"

16148 results found.

  1. GRB 251202A / EP251202a: Liverpool Telescope optical follow-up observations
  2. GRB 251129A / EP251129a: SVOM/VT optical color bluer
  3. EP251130a: MAO/AZT-22 optical observations
  4. GRB 251202A / EP251202a: SVOM/VT optical observation
  5. EP251202a/GRB 251202A: KAIT optical observations
  6. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  7. GRB251129A/EP251129a: Swift UVOT detection
  8. GRB 251201B: Kilonova-Catcher optical afterglow detection
  9. EP251130a: continued NOT optical observations indicate steep fading phase
  10. GRB 251122A/EP251122a: CrAO ZTSh optical observations
  11. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  12. GRB 251202A: GOTO optical afterglow detection
  13. GRB 251126A: SAO RAS optical marginal detection
  14. GRB 251202A: Swift-XRT afterglow detection
  15. EP251129a/GRB 251129A: NOWT Detection
  16. GRB 251126A: SVOM/VT optical observation
  17. EP251130a: SVOM/VT optical observation
  18. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  19. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  20. EP251202a/trigger 01709249064: Las Cumbres discovery of the optical counterpart
  21. GRB 251201A: SVOM/GRM observation of a burst
  22. GRB 251201B: SVOM/VT optical fading
  23. Swift GRB 251201B : MASTER optical counterpart detection
  24. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  25. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  26. GRB 251201B: Swift detection of a burst with an optical counterpart
  27. EP251130a: Mondy optical observations
  28. EP251130a: Optical detections with Kinder observations
  29. EP251130a: SAO RAS optical observations
  30. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  31. EP251130a: KAIT optical observations
  32. EP251130A: Optical observation from 1.3m DFOT
  33. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  34. EP251130a: JinShan optical observations
  35. GRB 251127A: SVOM/GRM observation
  36. EP251130a: Swift-XRT counterpart detection
  37. EP251130a: COLIBRÍ optical counterpart candidate
  38. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  39. GRB 251129A / EP251129a: OSN and CAHA optical follow-up
  40. GRB 251129A / EP251129a: SAO RAS optical observations
  41. GRB 251126A: SAO RAS optical observations
  42. GRB 251128A: SVOM/GRM observation of a long burst
  43. SVOM GRB 251129A : MASTER optical counterpart detection
  44. GRB 251129A: Swift-XRT afterglow detection
  45. GRB 251129A / EP251129a: SVOM/VT optical fading
  46. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  47. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  48. GRB 251129A: Correction to the position of the optical counterpar
  49. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  50. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  51. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  52. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  53. GRB 251126A: further SAO RAS optical observations
  54. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  55. GRB 251126A NUTTelA-TAO Early Measurements
  56. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  57. GRB251126A: MAO/AZT-22 optical observations
  58. GRB251126A: Continued optical observation from 1.3m DFOT
  59. GRB 251126A: Swift/UVOT Detection
  60. EP251124a: Pan-STARRS ri-band imaging and photometry
  61. GRB 251126A: Mondy and SAO RAS optical observations
  62. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  63. GRB 251126A: NOT optical observations
  64. GRB 251126A: 1.3m DFOT optical afterglow detection
  65. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  66. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  67. GRB 251126A: Kilonova-Catcher optical afterglow detection
  68. GRB 251126A: Asiago i-band detection
  69. GRB 251126A: Nanshan/HMT optical afterglow detection
  70. GRB 251126A: GIT discovery of the likely optical afterglow
  71. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  72. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  73. EP251124b: NOT r- and z-band optical upper limits
  74. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  75. EP251124a: Xinglong GWAC-F60A optical observation
  76. EP251124a: NOT r- and z-band optical upper limits
  77. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  78. EP251124a: Optical upper limit with Kinder observations
  79. EP251118A: 6 GHz VLA Detection
  80. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  81. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  82. EP251124a: GROWTH-India Telescope optical upper limits
  83. GRB 251122A/EP251122a: FTW optical and NIR observations
  84. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  85. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  86. EP251118A: 3.6m DOT optical afterglow detection
  87. GRB 251122A / EP251122a: EP-FXT counterpart detection
  88. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  89. GRB 251122A / EP251122a: WFST optical observations
  90. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  91. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  92. GRB 251122A / EP251122a: LCO optical upper limits
  93. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  94. EP251118a: Continued Optical Detection with Kinder observations
  95. EP251118a: Xinglong-2.16m optical observation
  96. EP251118A: 1.3m DFOT optical afterglow detection
  97. EP251118a / GRB 251118C: SAO RAS optical observations
  98. EP251118a: Optical detection with Kinder observations
  99. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  100. EP251118a / GRB 251118C: SVOM/VT optical observation

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