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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"

32763 results found.

  1. EP250830a: Global MASTER-Net observations report
  2. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  3. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  4. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  5. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  6. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  7. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  8. GRB 250830B: Swift ToO observations
  9. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  10. GRB 250828B: Swift-BAT refined analysis
  11. EP250821a: SOAR observations
  12. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  13. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  14. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  15. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  16. EP250828a: Optical counterpart detection with Kinder observations
  17. EP250828a: Liverpool Telescope upper limits
  18. Swift GRB 250828B: Global MASTER-Net observations report
  19. EP250828a: Global MASTER-Net observations report
  20. EP-WXT trigger 01709200800 : KAIT optical observations
  21. EP250828a: KAIT optical upper limit
  22. EP250827a: Swift/UVOT Detection
  23. EP250828a: NOT optical counterpart confirmation
  24. EP250828a: SVOM/VT optical candidate
  25. EP250828a: Seimei/TriCCS optical counterpart detection
  26. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  27. EP250828a: Optical upper limit with Kinder observations
  28. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  29. LIGO/Virgo/KAGRA S250818k: uGMRT 1.3 GHz observations of AT2025ulz
  30. EP250827a: LCO observations show fading optical counterpart
  31. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  32. GRID detection of GRB 250824A
  33. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  34. EP250827A: VLT/X-shooter redshift confirmation
  35. Fermi GRB 250827A: Global MASTER-Net observations report
  36. EP250827a: confirmation of optical rebrightening with LCO
  37. EP250827a: GOTO observation of the optical afterglow
  38. GRB 250826A: SVOM/GRM observation
  39. EP250827A: An optical rebrightening was detected by LCO.
  40. EP250827a: Swift-XRT counterpart detection
  41. LIGO/Virgo/KAGRA S250827l: Updated Sky localization
  42. EP250827a: TRT optical observations
  43. EP250827a / GRB 250827A: MASTER-OAFA OT observation
  44. EP250827a: Gemini-South redshift z = 1.613
  45. EP250827a: Global MASTER-Net observations report
  46. EP250827a: Las Cumbres independent detection of the optical counterpart
  47. EP250827a: Gemini-South optical counterpart detection
  48. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  49. Fermi GRB 250826A: Global MASTER-Net observations report
  50. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  51. EP250821a: Gemini GMOS Redshift Confirmation
  52. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  53. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Confirmation of Rebrightening of AT2025ulz
  54. Fermi GRB 250824B: Global MASTER-Net observations report
  55. LIGO/Virgo/KAGRA S250818k: VLA upper limits on AT2025ulz
  56. LIGO/Virgo/KAGRA S250818k: nature of the AT2025ulz/ZTF25abjmnnps OT
  57. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  58. GRB 250823A: Swift-BAT refined analysis
  59. LIGO/Virgo/KAGRA S250818k: Continued Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
  60. GRB 250821B: AstroSat CZTI detection
  61. GRB 250819A: AstroSat CZTI detection
  62. LIGO/Virgo/KAGRA S250818k: FTW Observations Show Continued Reddening of AT 2025ulz
  63. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  64. GRB 250821B: Insight-HXMT detection
  65. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  66. EP250821a: MeerKAT radio counterpart
  67. EP triggers 01709200706 and 01709200707: GOTO confirmation of flaring stars
  68. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  69. GRB 250823A: COLIBRÍ optical observations
  70. GRB 250823A: SVOM/VT optical observation
  71. GRB 250823A: Swift/UVOT Detection
  72. GRB 250823A: NOT optical observations
  73. LIGO/Virgo/KAGRA S250818k: CFH/MegaCam follow-up observation for AT2025ulz
  74. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  75. GRB 250823A: Fermi GBM Observation
  76. GRB 250818B: MeerKAT Detection
  77. GRB 250823A: LCOGT Optical Detection
  78. GRB 250823A: BOOTES6/DPRT early optical detection
  79. GRB 250823A: Liverpool Telescope optical detection
  80. Konus-Wind detection of GRB 250821B
  81. LIGO/Virgo/KAGRA S250818k: Rebrightening detected with Gemini/GMOS
  82. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  83. LIGO/Virgo/KAGRA S250818k: J-GEM follow-up observation for AT2025ulz
  84. LIGO/Virgo/KAGRA S250818k: PRIME nIR observations of AT2025ulz
  85. LIGO/Virgo/KAGRA S250818k: JinShan optical observations of AT2025ulz
  86. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  87. LIGO/Virgo/Kagra S250818k: STEP/T80N upper limits on 2025ulz
  88. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  89. GRB 250806A: Gemini observations of host galaxy candidate
  90. IPN triangulation of GRB 250821B (long/bright)
  91. GRB 250821A: Kilonova-Catcher optical upper limits
  92. EP250821a: Swift/XRT counterpart fading
  93. GRB 250812A: SVOM/ECLAIRs refined analysis
  94. GRB 250821A: Swift-BAT refined analysis
  95. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
  96. LIGO/Virgo/KAGRA S250818k: NOT optical observations of AT2025ulz
  97. EP250821a: Swift/UVOT further observations.
  98. EP250821a: VLT X-shooter spectroscopic redshift z = 0.577
  99. LIGO/Virgo/KAGRA S250818k: GRAWITA TNG NIR observations of AT2025ulz
  100. GRB 250821A: VLT/FORS2 Optical Observation

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