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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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subject:"Swift"
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28237 results found.

  1. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  2. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  3. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  4. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  5. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  6. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  7. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  8. GRB 250830B: MAXI/GSC detection
  9. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  10. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  11. GRB 250828B: Swift-BAT refined analysis
  12. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  13. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  14. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  15. EP250828a: Optical counterpart detection with Kinder observations
  16. EP250828a: Liverpool Telescope upper limits
  17. EP250828a: Global MASTER-Net observations report
  18. EP-WXT trigger 01709200800 : KAIT optical observations
  19. EP250828a: KAIT optical upper limit
  20. EP250827a: Swift/UVOT Detection
  21. EP250828a: NOT optical counterpart confirmation
  22. EP250828a: SVOM/VT optical candidate
  23. EP250828a: Seimei/TriCCS optical counterpart detection
  24. EP250828a: Optical upper limit with Kinder observations
  25. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  26. EP250827a: LCO observations show fading optical counterpart
  27. EP250828a: Einstein Probe detection of an X-ray transient
  28. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  29. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  30. EP250827a: confirmation of optical rebrightening with LCO
  31. GRB 250826A: SVOM/GRM observation
  32. EP250827A: An optical rebrightening was detected by LCO.
  33. EP250827a: Swift-XRT counterpart detection
  34. LIGO/Virgo/KAGRA S250827l: Updated Sky localization
  35. EP250827a: TRT optical observations
  36. EP250827a: Gemini-South redshift z = 1.613
  37. EP250827a: Einstein Probe detection of an X-ray transient
  38. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  39. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  40. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  41. Fermi GRB 250824B: Global MASTER-Net observations report
  42. LIGO/Virgo/KAGRA S250818k: nature of the AT2025ulz/ZTF25abjmnnps OT
  43. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  44. GRB 250823A: Swift-BAT refined analysis
  45. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  46. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  47. GRB 250823A: Swift-XRT refined Analysis
  48. EP250821a: MeerKAT radio counterpart
  49. GRB 250823A: COLIBRÍ optical observations
  50. GRB 250823A: SVOM/VT optical observation
  51. GRB 250823A: Swift/UVOT Detection
  52. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  53. GRB 250823A: Fermi GBM Observation
  54. GRB 250823A: Enhanced Swift-XRT position
  55. GRB 250823A: LCOGT Optical Detection
  56. GRB 250823A: Swift detection of a burst
  57. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  58. LIGO/Virgo/KAGRA S250818k: JinShan optical observations of AT2025ulz
  59. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  60. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  61. GRB 250806A: Gemini observations of host galaxy candidate
  62. GRB 250821A: Kilonova-Catcher optical upper limits
  63. EP250821a: Swift/XRT counterpart fading
  64. GRB 250821A: Swift-BAT refined analysis
  65. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
  66. LIGO/Virgo/KAGRA S250818k: NOT optical observations of AT2025ulz
  67. GRB 250821A: VLT/FORS2 Optical Observation
  68. GRB 250821B: SVOM/GRM observation
  69. EP250821a: SVOM/VT optical observation
  70. GRB 250821A: NOT z-band upper limit
  71. GRB 250821A: KAIT optical upper limit
  72. GRB 250821A: Swift-XRT refined Analysis
  73. GRB 250821B: Fermi GBM Detection
  74. GRB 250821B: BALROG localization (Fermi Trigger / GRB 250821672)
  75. GRB 250821A: Enhanced Swift-XRT position
  76. GRB 250821A: Swift/UVOT Upper Limits
  77. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  78. EP250821a: Swift XRT and UVOT counterpart detection
  79. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  80. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  81. GRB 250821A: LCOGT Optical Upper Limits
  82. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  83. GRB 250821A: Swift detection of a burst
  84. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  85. EP250821a: Einstein Probe detection of an X-ray transient
  86. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  87. LIGO/Virgo/KAGRA S250818k: WINTER J-band observations of AT 2025ulz
  88. LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz
  89. GRB 250814A: Swift/UVOT Upper Limits
  90. GRB 250813B: Swift/UVOT Upper Limit
  91. IPN triangulation of GRB 250816A (short)
  92. IPN triangulation of GRB 250814C (short)
  93. IPN triangulation of GRB 250804B (short)
  94. GRB 250818B: Kilonova-Catcher optical afterglow detection
  95. LIGO/Virgo/KAGRA S250818k: AstroSat CZTI non-detection and upper limits
  96. LIGO/Virgo/KAGRA S250818k: Upper limits from Fermi-GBM Observations
  97. LIGO/Virgo/KAGRA S250818k: Updated Sky localization and EM Bright Classification
  98. LIGO/Virgo/KAGRA S250818k: Pan-STARRS pre-detection limits for AT2025ulz
  99. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  100. GRB 250818B: Swift/UVOT Detection

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