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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"

20387 results found.

  1. EP detected a brightening of LMXB 1ES 1735-26.9
  2. GRB 250905A: KAIT optical upper limit
  3. GRB 250905A: Swift detection of a burst
  4. GRB 250904A: Enhanced Swift-XRT position
  5. IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
  6. GRB 250904A: TRT optical counterpart detection
  7. GRB 250904A: Swift detection of a burst
  8. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  9. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  10. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  11. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  12. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  13. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  14. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  15. GRB 250903A: LCO optical observation
  16. GRB 250903A: LCO optical afterglow detection
  17. GRB 250903A: SVOM/VT optical confirmation with VHF data
  18. EP250901a: Mondy, Assy and SAO RAS optical limits
  19. GRB 250903A: TRT optical counterpart detection
  20. GRB 250903A: SVOM detection of a burst
  21. EP250903a: TRT optical observations
  22. EP250903a: Einstein Probe detection of an X-ray transient
  23. EP 250827B: Detection of supernova counterpart by LCO.
  24. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  25. GRB 250902B: SVOM/GRM observation
  26. EP250827b: SVOM/VT observation of AT 2025wkm
  27. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  28. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  29. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  30. GRB 250901A: Swift/UVOT Upper Limit
  31. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  32. GRB 250830B: Swift-XRT afterglow detection
  33. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  34. GRB 250902A: SVOM/GRM observation
  35. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  36. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  37. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  38. GRB 250901A: SVOM/VT optical afterglow with VHF data
  39. GRB 250901A: Swift-XRT afterglow detection
  40. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  41. GRB 250901A: LCO optical upper limit
  42. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  43. EP250831a: NOT optical observations and tentative afterglow candidate
  44. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  45. GRB 250901A: SVOM detection of a burst
  46. EP250901a: Mephisto optical upper limits
  47. GRB 250830C: AstroSat CZTI detection of a long burst
  48. EP250901a: Einstein Probe detection of an X-ray transient
  49. EP250831a: EP-WXT detection of a fast X-ray transient
  50. GRB 250831A: Swift-XRT counterpart detection
  51. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  52. GRB 250831A: SVOM/VT upper limit with VHF data
  53. GRB 250831A: SVOM detection of a soft burst
  54. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  55. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  56. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  57. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  58. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  59. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  60. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  61. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  62. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  63. GRB 250808B: SVOM detection of a burst through offline search
  64. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  65. EP250828a: Optical counterpart detection with Kinder observations
  66. EP250828a: Liverpool Telescope upper limits
  67. EP-WXT trigger 01709200800 : KAIT optical observations
  68. EP250828a: KAIT optical upper limit
  69. EP250827a: Swift/UVOT Detection
  70. EP250828a: NOT optical counterpart confirmation
  71. EP250828a: SVOM/VT optical candidate
  72. EP250828a: Seimei/TriCCS optical counterpart detection
  73. EP250828a: Optical upper limit with Kinder observations
  74. EP250828a: Einstein Probe detection of an X-ray transient
  75. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  76. GRID detection of GRB 250824A
  77. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  78. EP250827a: confirmation of optical rebrightening with LCO
  79. GRB 250826A: SVOM/GRM observation
  80. EP250827A: An optical rebrightening was detected by LCO.
  81. EP250827a: TRT optical observations
  82. EP250827a: Einstein Probe detection of an X-ray transient
  83. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  84. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  85. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  86. Fermi GRB 250824B: Global MASTER-Net observations report
  87. LIGO/Virgo/KAGRA S250818k: VLA upper limits on AT2025ulz
  88. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  89. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  90. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  91. EP250821a: MeerKAT radio counterpart
  92. GRB 250823A: COLIBRÍ optical observations
  93. GRB 250823A: SVOM/VT optical observation
  94. GRB 250823A: Swift/UVOT Detection
  95. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  96. GRB 250823A: Enhanced Swift-XRT position
  97. GRB 250823A: LCOGT Optical Detection
  98. GRB 250823A: Swift detection of a burst
  99. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  100. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz

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