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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"
body:"GRB"
submitter:"Judith Racusin"

41968 results found.

  1. GRB 250819A: AstroSat CZTI detection
  2. LIGO/Virgo/KAGRA S250818k: FTW Observations Show Continued Reddening of AT 2025ulz
  3. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  4. GRB 250821B: Insight-HXMT detection
  5. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  6. GRB 250823A: Swift-XRT refined Analysis
  7. EP250821a: MeerKAT radio counterpart
  8. EP triggers 01709200706 and 01709200707: GOTO confirmation of flaring stars
  9. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  10. GRB 250824B: Fermi GBM Final Real-time Localization
  11. The EP-WXT trigger 01709200707 is likely a flaring star
  12. GRB 250823A: COLIBRÍ optical observations
  13. The EP-WXT trigger 01709200706 is likely a flaring star
  14. GRB 250823A: SVOM/VT optical observation
  15. GRB 250824A: Fermi GBM Final Real-time Localization
  16. GRB 250823A: Swift/UVOT Detection
  17. GRB 250823A: NOT optical observations
  18. LIGO/Virgo/KAGRA S250818k: CFH/MegaCam follow-up observation for AT2025ulz
  19. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  20. GRB 250823A: Fermi GBM Observation
  21. GRB 250818B: MeerKAT Detection
  22. GRB 250823A: Enhanced Swift-XRT position
  23. GRB 250823A: LCOGT Optical Detection
  24. GRB 250823A: Liverpool Telescope optical detection
  25. GRB 250823A: Swift detection of a burst
  26. GRB 250823A: Fermi GBM Final Real-time Localization
  27. Swift GRB250823.84: Global MASTER-Net observations report
  28. Konus-Wind detection of GRB 250821B
  29. LIGO/Virgo/KAGRA S250818k: Rebrightening detected with Gemini/GMOS
  30. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  31. LIGO/Virgo/KAGRA S250818k: J-GEM follow-up observation for AT2025ulz
  32. LIGO/Virgo/KAGRA S250818k: PRIME nIR observations of AT2025ulz
  33. LIGO/Virgo/KAGRA S250818k: JinShan optical observations of AT2025ulz
  34. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  35. LIGO/Virgo/Kagra S250818k: STEP/T80N upper limits on 2025ulz
  36. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  37. GRB 250806A: Gemini observations of host galaxy candidate
  38. IPN triangulation of GRB 250821B (long/bright)
  39. GRB 250821A: Kilonova-Catcher optical upper limits
  40. EP250821a: Swift/XRT counterpart fading
  41. GRB 250812A: SVOM/ECLAIRs refined analysis
  42. GRB 250821A: Swift-BAT refined analysis
  43. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
  44. LIGO/Virgo/KAGRA S250818k: NOT optical observations of AT2025ulz
  45. EP250821a: Swift/UVOT further observations.
  46. EP250821a: VLT X-shooter spectroscopic redshift z = 0.577
  47. LIGO/Virgo/KAGRA S250818k: GRAWITA TNG NIR observations of AT2025ulz
  48. GRB 250821A: VLT/FORS2 Optical Observation
  49. GRB 250821A: GECAM-B detection
  50. GRB 250821B: SVOM/GRM observation
  51. EP250821a: SVOM/VT optical observation
  52. Fermi GRB 250821B: Global MASTER-Net observations report
  53. GRB 250821A: NOT z-band upper limit
  54. GRB 250821C: Fermi GBM Final Real-time Localization
  55. GRB 250821A: KAIT optical upper limit
  56. LIGO/Virgo/KAGRA S250818k: Continued fading and reddening of AT2025ulz from Keck/LRIS imaging observations
  57. GRB 250821A: Swift-XRT refined Analysis
  58. Swift GRB 250821A: Global MASTER-Net observations report
  59. GRB 250821B: Fermi GBM Detection
  60. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of AT 2025ulz
  61. GRB 250821B: BALROG localization (Fermi Trigger / GRB 250821672)
  62. LIGO/Virgo/KAGRA S250818k : Tautenburg observations, upper limits
  63. GRB 250821B: Fermi GBM Final Localization of a Bright Burst
  64. GRB 250821A: Enhanced Swift-XRT position
  65. GRB 250821A: Swift/UVOT Upper Limits
  66. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  67. EP250821a: Swift XRT and UVOT counterpart detection
  68. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  69. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  70. GRB 250821A: LCOGT Optical Upper Limits
  71. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  72. LIGO/Virgo/KAGRA S250818k: 10 GHz VLA observations of AT2025ulz
  73. GRB 250821A: Prompt enhanced Swift-XRT position
  74. GRB 250821A: Swift detection of a burst
  75. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  76. LIGO/Virgo/KAGRA S250818k: EP/FXT observation of AT 2025ulz
  77. EP250821a: Einstein Probe detection of an X-ray transient
  78. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  79. GRB 250819A: Insight-HXMT detection
  80. LIGO/Virgo/KAGRA S250818k: WINTER J-band observations of AT 2025ulz
  81. GRB 250818B: 10 GHz VLA detection
  82. LIGO/Virgo/KAGRA S250818k: Pan-STARRS grizy-band imaging and photometry of AT2025ulz
  83. LIGO/Virgo/KAGRA S250818k: Swift observations of AT 2025ulz
  84. LIGO/Virgo/KAGRA S250818k: Multi-band Gemini GMOS Detections
  85. LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz
  86. GRB 250814A: Swift/UVOT Upper Limits
  87. GRB 250813B: Swift/UVOT Upper Limit
  88. GRB 250818B: FTW optical and NIR observations show reddening of the counterpart
  89. GRB 250818B: Kilonova-Catcher optical afterglow detection
  90. LIGO/Virgo/KAGRA S250818k: AstroSat CZTI non-detection and upper limits
  91. GRB 250818B: Liverpool Telescope optical detections
  92. LIGO/Virgo/KAGRA S250818k: Upper limits from Fermi-GBM Observations
  93. LIGO/Virgo/KAGRA S250818k: Updated Sky localization and EM Bright Classification
  94. LIGO/Virgo/KAGRA S250818k: Pan-STARRS pre-detection limits for AT2025ulz
  95. GRB 250818A: AstroSat CZTI detection
  96. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  97. LIGO/Virgo/KAGRA S250818k: Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
  98. GRB 250818B: Swift/UVOT Detection
  99. LIGO/Virgo/KAGRA S250818k: FTW Fast reddening of AT 2025ulz
  100. GRB 250820A: Fermi GBM Final Real-time Localization

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