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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"

26669 results found.

  1. LIGO/Virgo/KAGRA S250818k: uGMRT 1.3 GHz observations of AT2025ulz
  2. EP250828a: Einstein Probe detection of an X-ray transient
  3. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  4. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  5. EP250827a: confirmation of optical rebrightening with LCO
  6. GRB 250826A: SVOM/GRM observation
  7. EP250827A: An optical rebrightening was detected by LCO.
  8. EP250827a: Swift-XRT counterpart detection
  9. The EP-WXT trigger 01709200800 is likely a flaring star
  10. EP250827a: TRT optical observations
  11. EP250827a: BOOTES-7 early optical dectection
  12. EP250827a: Einstein Probe detection of an X-ray transient
  13. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  14. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  15. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  16. LIGO/Virgo/KAGRA S250818k: VLA upper limits on AT2025ulz
  17. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  18. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  19. GRB 250823A: Swift-XRT refined Analysis
  20. EP250821a: MeerKAT radio counterpart
  21. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  22. The EP-WXT trigger 01709200707 is likely a flaring star
  23. GRB 250823A: COLIBRÍ optical observations
  24. The EP-WXT trigger 01709200706 is likely a flaring star
  25. GRB 250823A: SVOM/VT optical observation
  26. GRB 250823A: Swift/UVOT Detection
  27. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  28. GRB 250823A: Fermi GBM Observation
  29. GRB 250823A: Enhanced Swift-XRT position
  30. GRB 250823A: LCOGT Optical Detection
  31. GRB 250823A: Swift detection of a burst
  32. Konus-Wind detection of GRB 250821B
  33. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  34. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  35. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  36. IPN triangulation of GRB 250821B (long/bright)
  37. GRB 250821A: Kilonova-Catcher optical upper limits
  38. EP250821a: Swift/XRT counterpart fading
  39. GRB 250812A: SVOM/ECLAIRs refined analysis
  40. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
  41. GRB 250821A: VLT/FORS2 Optical Observation
  42. GRB 250821B: SVOM/GRM observation
  43. EP250821a: SVOM/VT optical observation
  44. GRB 250821A: NOT z-band upper limit
  45. GRB 250821A: KAIT optical upper limit
  46. GRB 250821A: Swift-XRT refined Analysis
  47. GRB 250821B: Fermi GBM Detection
  48. GRB 250821B: BALROG localization (Fermi Trigger / GRB 250821672)
  49. GRB 250821A: Enhanced Swift-XRT position
  50. GRB 250821A: Swift/UVOT Upper Limits
  51. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  52. EP250821a: Swift XRT and UVOT counterpart detection
  53. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  54. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  55. GRB 250821A: LCOGT Optical Upper Limits
  56. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  57. GRB 250821A: Swift detection of a burst
  58. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  59. LIGO/Virgo/KAGRA S250818k: EP/FXT observation of AT 2025ulz
  60. EP250821a: Einstein Probe detection of an X-ray transient
  61. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  62. LIGO/Virgo/KAGRA S250818k: WINTER J-band observations of AT 2025ulz
  63. LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz
  64. GRB 250814A: Swift/UVOT Upper Limits
  65. GRB 250813B: Swift/UVOT Upper Limit
  66. IPN triangulation of GRB 250816A (short)
  67. IPN triangulation of GRB 250814C (short)
  68. IPN triangulation of GRB 250804B (short)
  69. GRB 250818B: Kilonova-Catcher optical afterglow detection
  70. LIGO/Virgo/KAGRA S250818k: AstroSat CZTI non-detection and upper limits
  71. GRB 250818B: Liverpool Telescope optical detections
  72. LIGO/Virgo/KAGRA S250818k: Upper limits from Fermi-GBM Observations
  73. LIGO/Virgo/KAGRA S250818k: Updated Sky localization and EM Bright Classification
  74. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  75. GRB 250818B: Swift/UVOT Detection
  76. GRB 250818B: SAO RAS optical observations
  77. GRB 250818A: Swift-XRT refined Analysis
  78. GRB 250818B: EP-FXT counterpart detection
  79. GRB 250818B: KAIT optical observations
  80. GRB 250818A: Swift/UVOT Upper Limits
  81. GRB 250818A: Enhanced Swift-XRT position
  82. GRB 250813B: SVOM/ECLAIRs refined analysis
  83. GRB 250818A: Fermi GBM Observation
  84. LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations
  85. GRB 250814A: Further GRAWITA TNG NIR observations
  86. GRB 250818B: Swift-XRT afterglow detection
  87. GRB 250818B: SVOM detection of a short burst
  88. LIGO/Virgo/KAGRA S250818t: Identification of a GW compact binary merger candidate
  89. GRB 250818A: Swift detection of a burst
  90. sb25081602: Swift-XRT observations
  91. GRB 250816A: SVOM/GRM observation of a short burst
  92. SVOM/sb25081602: detection of a likely X-ray transient
  93. GRB 250813B: Liverpool Telescope optical upper limits
  94. GRB 250814A: Further COLIBRÍ optical upper limit
  95. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  96. GRB 250814A: GRAWITA TNG NIR observations
  97. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  98. GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  99. GRB250814A: TRT optical upper limits
  100. GRB 250814B: SVOM/GRM observation

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