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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"

42521 results found.

  1. The EP-WXT trigger 01709200800 is likely a flaring star
  2. EP250827a: TRT optical observations
  3. EP250827a: BOOTES-7 early optical dectection
  4. EP250827a / GRB 250827A: MASTER-OAFA OT observation
  5. EP250827a: Gemini-South redshift z = 1.613
  6. EP250827a: Global MASTER-Net observations report
  7. EP250827a: Las Cumbres independent detection of the optical counterpart
  8. EP250827a: Gemini-South optical counterpart detection
  9. EP250827a: Einstein Probe detection of an X-ray transient
  10. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  11. Fermi GRB 250826A: Global MASTER-Net observations report
  12. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  13. EP250821a: Gemini GMOS Redshift Confirmation
  14. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  15. Fermi trigger No 777883624: Global MASTER-Net observations report
  16. GRB 250826A: Fermi GBM Final Real-time Localization
  17. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Confirmation of Rebrightening of AT2025ulz
  18. Fermi GRB 250824B: Global MASTER-Net observations report
  19. LIGO/Virgo/KAGRA S250818k: VLA upper limits on AT2025ulz
  20. LIGO/Virgo/KAGRA S250818k: nature of the AT2025ulz/ZTF25abjmnnps OT
  21. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  22. GRB 250823A: Swift-BAT refined analysis
  23. LIGO/Virgo/KAGRA S250818k: Continued Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
  24. GRB 250821B: AstroSat CZTI detection
  25. GRB 250819A: AstroSat CZTI detection
  26. LIGO/Virgo/KAGRA S250818k: FTW Observations Show Continued Reddening of AT 2025ulz
  27. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  28. GRB 250821B: Insight-HXMT detection
  29. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  30. GRB 250823A: Swift-XRT refined Analysis
  31. EP250821a: MeerKAT radio counterpart
  32. EP triggers 01709200706 and 01709200707: GOTO confirmation of flaring stars
  33. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  34. GRB 250824B: Fermi GBM Final Real-time Localization
  35. The EP-WXT trigger 01709200707 is likely a flaring star
  36. GRB 250823A: COLIBRÍ optical observations
  37. The EP-WXT trigger 01709200706 is likely a flaring star
  38. GRB 250823A: SVOM/VT optical observation
  39. GRB 250824A: Fermi GBM Final Real-time Localization
  40. GRB 250823A: Swift/UVOT Detection
  41. GRB 250823A: NOT optical observations
  42. LIGO/Virgo/KAGRA S250818k: CFH/MegaCam follow-up observation for AT2025ulz
  43. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  44. GRB 250823A: Fermi GBM Observation
  45. GRB 250818B: MeerKAT Detection
  46. GRB 250823A: Enhanced Swift-XRT position
  47. GRB 250823A: LCOGT Optical Detection
  48. GRB 250823A: BOOTES6/DPRT early optical detection
  49. GRB 250823A: Liverpool Telescope optical detection
  50. GRB 250823A: Swift detection of a burst
  51. GRB 250823A: Fermi GBM Final Real-time Localization
  52. Swift GRB250823.84: Global MASTER-Net observations report
  53. Konus-Wind detection of GRB 250821B
  54. LIGO/Virgo/KAGRA S250818k: Rebrightening detected with Gemini/GMOS
  55. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  56. LIGO/Virgo/KAGRA S250818k: J-GEM follow-up observation for AT2025ulz
  57. LIGO/Virgo/KAGRA S250818k: PRIME nIR observations of AT2025ulz
  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: STEP/T80N upper limits on 2025ulz
  61. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  62. GRB 250806A: Gemini observations of host galaxy candidate
  63. IPN triangulation of GRB 250821B (long/bright)
  64. GRB 250821A: Kilonova-Catcher optical upper limits
  65. EP250821a: Swift/XRT counterpart fading
  66. GRB 250812A: SVOM/ECLAIRs refined analysis
  67. GRB 250821A: Swift-BAT refined analysis
  68. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
  69. LIGO/Virgo/KAGRA S250818k: NOT optical observations of AT2025ulz
  70. EP250821a: Swift/UVOT further observations.
  71. EP250821a: VLT X-shooter spectroscopic redshift z = 0.577
  72. LIGO/Virgo/KAGRA S250818k: GRAWITA TNG NIR observations of AT2025ulz
  73. GRB 250821A: VLT/FORS2 Optical Observation
  74. GRB 250821A: GECAM-B detection
  75. GRB 250821B: SVOM/GRM observation
  76. EP250821a: SVOM/VT optical observation
  77. Fermi GRB 250821B: Global MASTER-Net observations report
  78. GRB 250821A: NOT z-band upper limit
  79. GRB 250821C: Fermi GBM Final Real-time Localization
  80. GRB 250821A: KAIT optical upper limit
  81. LIGO/Virgo/KAGRA S250818k: Continued fading and reddening of AT2025ulz from Keck/LRIS imaging observations
  82. GRB 250821A: Swift-XRT refined Analysis
  83. Swift GRB 250821A: Global MASTER-Net observations report
  84. GRB 250821B: Fermi GBM Detection
  85. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of AT 2025ulz
  86. GRB 250821B: BALROG localization (Fermi Trigger / GRB 250821672)
  87. LIGO/Virgo/KAGRA S250818k : Tautenburg observations, upper limits
  88. GRB 250821B: Fermi GBM Final Localization of a Bright Burst
  89. GRB 250821A: Enhanced Swift-XRT position
  90. GRB 250821A: Swift/UVOT Upper Limits
  91. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  92. EP250821a: Swift XRT and UVOT counterpart detection
  93. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  94. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  95. GRB 250821A: LCOGT Optical Upper Limits
  96. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  97. LIGO/Virgo/KAGRA S250818k: 10 GHz VLA observations of AT2025ulz
  98. GRB 250821A: Prompt enhanced Swift-XRT position
  99. GRB 250821A: Swift detection of a burst
  100. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz

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