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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"
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submitter:"Judith Racusin"

28233 results found.

  1. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  2. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  3. GRB 250830B: MAXI/GSC detection
  4. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  5. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  6. GRB 250828B: Swift-BAT refined analysis
  7. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  8. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  9. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  10. EP250828a: Optical counterpart detection with Kinder observations
  11. EP250828a: Liverpool Telescope upper limits
  12. EP250828a: Global MASTER-Net observations report
  13. EP-WXT trigger 01709200800 : KAIT optical observations
  14. EP250828a: KAIT optical upper limit
  15. EP250827a: Swift/UVOT Detection
  16. EP250828a: NOT optical counterpart confirmation
  17. EP250828a: SVOM/VT optical candidate
  18. EP250828a: Seimei/TriCCS optical counterpart detection
  19. EP250828a: Optical upper limit with Kinder observations
  20. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  21. EP250827a: LCO observations show fading optical counterpart
  22. EP250828a: Einstein Probe detection of an X-ray transient
  23. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  24. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  25. EP250827a: confirmation of optical rebrightening with LCO
  26. GRB 250826A: SVOM/GRM observation
  27. EP250827A: An optical rebrightening was detected by LCO.
  28. EP250827a: Swift-XRT counterpart detection
  29. LIGO/Virgo/KAGRA S250827l: Updated Sky localization
  30. EP250827a: TRT optical observations
  31. EP250827a: Gemini-South redshift z = 1.613
  32. EP250827a: Einstein Probe detection of an X-ray transient
  33. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  34. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  35. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  36. Fermi GRB 250824B: Global MASTER-Net observations report
  37. LIGO/Virgo/KAGRA S250818k: nature of the AT2025ulz/ZTF25abjmnnps OT
  38. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  39. GRB 250823A: Swift-BAT refined analysis
  40. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  41. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  42. GRB 250823A: Swift-XRT refined Analysis
  43. EP250821a: MeerKAT radio counterpart
  44. GRB 250823A: COLIBRÍ optical observations
  45. GRB 250823A: SVOM/VT optical observation
  46. GRB 250823A: Swift/UVOT Detection
  47. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  48. GRB 250823A: Fermi GBM Observation
  49. GRB 250823A: Enhanced Swift-XRT position
  50. GRB 250823A: LCOGT Optical Detection
  51. GRB 250823A: Swift detection of a burst
  52. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  53. LIGO/Virgo/KAGRA S250818k: JinShan optical observations of AT2025ulz
  54. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  55. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  56. GRB 250806A: Gemini observations of host galaxy candidate
  57. GRB 250821A: Kilonova-Catcher optical upper limits
  58. EP250821a: Swift/XRT counterpart fading
  59. GRB 250821A: Swift-BAT refined analysis
  60. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
  61. LIGO/Virgo/KAGRA S250818k: NOT optical observations of AT2025ulz
  62. GRB 250821A: VLT/FORS2 Optical Observation
  63. GRB 250821B: SVOM/GRM observation
  64. EP250821a: SVOM/VT optical observation
  65. GRB 250821A: NOT z-band upper limit
  66. GRB 250821A: KAIT optical upper limit
  67. GRB 250821A: Swift-XRT refined Analysis
  68. GRB 250821B: Fermi GBM Detection
  69. GRB 250821B: BALROG localization (Fermi Trigger / GRB 250821672)
  70. GRB 250821A: Enhanced Swift-XRT position
  71. GRB 250821A: Swift/UVOT Upper Limits
  72. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  73. EP250821a: Swift XRT and UVOT counterpart detection
  74. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  75. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  76. GRB 250821A: LCOGT Optical Upper Limits
  77. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  78. GRB 250821A: Swift detection of a burst
  79. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  80. EP250821a: Einstein Probe detection of an X-ray transient
  81. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  82. LIGO/Virgo/KAGRA S250818k: WINTER J-band observations of AT 2025ulz
  83. LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz
  84. GRB 250814A: Swift/UVOT Upper Limits
  85. GRB 250813B: Swift/UVOT Upper Limit
  86. IPN triangulation of GRB 250816A (short)
  87. IPN triangulation of GRB 250814C (short)
  88. IPN triangulation of GRB 250804B (short)
  89. GRB 250818B: Kilonova-Catcher optical afterglow detection
  90. LIGO/Virgo/KAGRA S250818k: AstroSat CZTI non-detection and upper limits
  91. LIGO/Virgo/KAGRA S250818k: Upper limits from Fermi-GBM Observations
  92. LIGO/Virgo/KAGRA S250818k: Updated Sky localization and EM Bright Classification
  93. LIGO/Virgo/KAGRA S250818k: Pan-STARRS pre-detection limits for AT2025ulz
  94. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  95. GRB 250818B: Swift/UVOT Detection
  96. GRB 250818B: optical afterglow detection with Lesedi (GOTO25fzq)
  97. GRB 250818B: SAO RAS optical observations
  98. GRB 250818A: Swift-XRT refined Analysis
  99. GRB 250818B: EP-FXT counterpart detection
  100. GRB 250818A: Swift-BAT refined analysis

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