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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"

32693 results found.

  1. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  2. EP250827b: Liverpool Telescope observations
  3. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  4. GRB 250902A: SVOM/GRM observation
  5. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  6. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  7. GRB 250901A: EP-FXT follow-up observation
  8. GRB 250901A: NOT optical observations
  9. GRB 250901A: SVOM/VT optical afterglow with VHF data
  10. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  11. GRB 250901A: LCO optical upper limit
  12. EP250827b: Swift observations of AT 2025wkm
  13. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  14. EP250827b: Gemini Spectroscopy of AT 2025wkm
  15. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  16. EP250831a: NOT optical observations and tentative afterglow candidate
  17. EP250827b: FTW Observations of AT 2025wkm
  18. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  19. GRB 250830C: Insight-HXMT detection
  20. EP250901a: Mephisto optical upper limits
  21. EP250901a: Global MASTER-Net observations report
  22. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  23. EP250831a: EP-FXT follow-up observation
  24. EP250831a: Swift-XRT observations
  25. EP250831a: Global MASTER-Net observations report
  26. GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
  27. GRB 250831A: Swift-XRT counterpart detection
  28. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  29. GRB 250831A: SVOM/VT upper limit with VHF data
  30. EP250830a: Global MASTER-Net observations report
  31. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  32. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  33. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  34. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  35. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  36. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  37. GRB 250830B: Swift ToO observations
  38. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  39. GRB 250828B: Swift-BAT refined analysis
  40. EP250821a: SOAR observations
  41. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  42. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  43. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  44. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  45. EP250828a: Optical counterpart detection with Kinder observations
  46. EP250828a: Liverpool Telescope upper limits
  47. Swift GRB 250828B: Global MASTER-Net observations report
  48. EP250828a: Global MASTER-Net observations report
  49. EP-WXT trigger 01709200800 : KAIT optical observations
  50. EP250828a: KAIT optical upper limit
  51. EP250827a: Swift/UVOT Detection
  52. EP250828a: NOT optical counterpart confirmation
  53. EP250828a: SVOM/VT optical candidate
  54. EP250828a: Seimei/TriCCS optical counterpart detection
  55. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  56. EP250828a: Optical upper limit with Kinder observations
  57. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  58. LIGO/Virgo/KAGRA S250818k: uGMRT 1.3 GHz observations of AT2025ulz
  59. EP250827a: LCO observations show fading optical counterpart
  60. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  61. GRID detection of GRB 250824A
  62. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  63. EP250827A: VLT/X-shooter redshift confirmation
  64. Fermi GRB 250827A: Global MASTER-Net observations report
  65. EP250827a: confirmation of optical rebrightening with LCO
  66. EP250827a: GOTO observation of the optical afterglow
  67. GRB 250826A: SVOM/GRM observation
  68. EP250827A: An optical rebrightening was detected by LCO.
  69. EP250827a: Swift-XRT counterpart detection
  70. LIGO/Virgo/KAGRA S250827l: Updated Sky localization
  71. EP250827a: TRT optical observations
  72. EP250827a / GRB 250827A: MASTER-OAFA OT observation
  73. EP250827a: Gemini-South redshift z = 1.613
  74. EP250827a: Global MASTER-Net observations report
  75. EP250827a: Las Cumbres independent detection of the optical counterpart
  76. EP250827a: Gemini-South optical counterpart detection
  77. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  78. Fermi GRB 250826A: Global MASTER-Net observations report
  79. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  80. EP250821a: Gemini GMOS Redshift Confirmation
  81. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  82. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Confirmation of Rebrightening of AT2025ulz
  83. Fermi GRB 250824B: Global MASTER-Net observations report
  84. LIGO/Virgo/KAGRA S250818k: VLA upper limits on AT2025ulz
  85. LIGO/Virgo/KAGRA S250818k: nature of the AT2025ulz/ZTF25abjmnnps OT
  86. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  87. GRB 250823A: Swift-BAT refined analysis
  88. LIGO/Virgo/KAGRA S250818k: Continued Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
  89. GRB 250821B: AstroSat CZTI detection
  90. GRB 250819A: AstroSat CZTI detection
  91. LIGO/Virgo/KAGRA S250818k: FTW Observations Show Continued Reddening of AT 2025ulz
  92. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  93. GRB 250821B: Insight-HXMT detection
  94. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  95. EP250821a: MeerKAT radio counterpart
  96. EP triggers 01709200706 and 01709200707: GOTO confirmation of flaring stars
  97. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  98. GRB 250823A: COLIBRÍ optical observations
  99. GRB 250823A: SVOM/VT optical observation
  100. GRB 250823A: Swift/UVOT Detection

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