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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. 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"

19807 results found.

  1. LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
  2. IceCube-250905A: Upper limits from a search for additional neutrino events in IceCube
  3. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  4. EP250905a: Liverpool Telescope i-band upper limits
  5. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  6. EP250905a: Liverpool Telescope observations
  7. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  8. EP250905b: EP-WXT detection of a fast X-ray transient
  9. EP250905a: JinShan likely optical counterpart detection
  10. GRB 250905A: Swift/UVOT Upper Limits
  11. GRB 250901A - SVOM/ECLAIRs refined analysis
  12. EP250905a: Einstein Probe detection of an X-ray transient
  13. GRB250904A: Liverpool Telescope upper limits
  14. GRB 250905A: Enhanced Swift-XRT position
  15. GRB 250904A: Swift/UVOT Detection
  16. GRB 250903A: Swift/UVOT detection
  17. EP detected a brightening of LMXB 1ES 1735-26.9
  18. GRB 250905A: KAIT optical upper limit
  19. GRB 250905A: Swift detection of a burst
  20. GRB 250904A: Enhanced Swift-XRT position
  21. IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
  22. GRB 250904A: TRT optical counterpart detection
  23. GRB 250904A: Swift detection of a burst
  24. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  25. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  26. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  27. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  28. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  29. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  30. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  31. GRB 250903A: LCO optical observation
  32. GRB 250903A: LCO optical afterglow detection
  33. GRB 250903A: SVOM/VT optical confirmation with VHF data
  34. EP250901a: Mondy, Assy and SAO RAS optical limits
  35. GRB 250903A: TRT optical counterpart detection
  36. GRB 250903A: SVOM detection of a burst
  37. EP250903a: TRT optical observations
  38. EP250903a: Einstein Probe detection of an X-ray transient
  39. EP 250827B: Detection of supernova counterpart by LCO.
  40. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  41. GRB 250902B: SVOM/GRM observation
  42. EP250827b: SVOM/VT observation of AT 2025wkm
  43. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  44. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  45. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  46. GRB 250901A: Swift/UVOT Upper Limit
  47. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  48. GRB 250830B: Swift-XRT afterglow detection
  49. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  50. GRB 250902A: SVOM/GRM observation
  51. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  52. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  53. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  54. GRB 250901A: SVOM/VT optical afterglow with VHF data
  55. GRB 250901A: Swift-XRT afterglow detection
  56. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  57. GRB 250901A: LCO optical upper limit
  58. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  59. EP250831a: NOT optical observations and tentative afterglow candidate
  60. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  61. GRB 250901A: SVOM detection of a burst
  62. EP250901a: Mephisto optical upper limits
  63. GRB 250830C: AstroSat CZTI detection of a long burst
  64. EP250901a: Einstein Probe detection of an X-ray transient
  65. EP250831a: EP-WXT detection of a fast X-ray transient
  66. GRB 250831A: Swift-XRT counterpart detection
  67. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  68. GRB 250831A: SVOM/VT upper limit with VHF data
  69. GRB 250831A: SVOM detection of a soft burst
  70. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  71. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  72. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  73. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  74. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  75. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  76. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  77. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  78. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  79. GRB 250808B: SVOM detection of a burst through offline search
  80. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  81. EP250828a: Optical counterpart detection with Kinder observations
  82. EP250828a: Liverpool Telescope upper limits
  83. EP-WXT trigger 01709200800 : KAIT optical observations
  84. EP250828a: KAIT optical upper limit
  85. EP250827a: Swift/UVOT Detection
  86. EP250828a: NOT optical counterpart confirmation
  87. EP250828a: SVOM/VT optical candidate
  88. EP250828a: Seimei/TriCCS optical counterpart detection
  89. EP250828a: Optical upper limit with Kinder observations
  90. EP250828a: Einstein Probe detection of an X-ray transient
  91. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  92. GRID detection of GRB 250824A
  93. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  94. EP250827a: confirmation of optical rebrightening with LCO
  95. GRB 250826A: SVOM/GRM observation
  96. EP250827A: An optical rebrightening was detected by LCO.
  97. EP250827a: TRT optical observations
  98. EP250827a: Einstein Probe detection of an X-ray transient
  99. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  100. GRB 250806A: HiPERCAM/GTC limits on a possible supernova

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