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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"

7420 results found.

  1. LIGO/Virgo/KAGRA S240505av: Upper limits from Swift/BAT-GUANO
  2. GRB 240513A: Tiled Swift observations
  3. LIGO/Virgo/KAGRA S240513ei: Identification of a GW compact binary merger candidate
  4. LIGO/Virgo/KAGRA S240513cx: Coverage and upper limits from MAXI/GSC observations
  5. LIGO/Virgo/KAGRA S240512r: Updated Sky localization and EM Bright Classification
  6. LIGO/Virgo/KAGRA S240512r: Identification of a GW compact binary merger candidate
  7. GRB 240511A: Swift detection of a burst
  8. LIGO/Virgo/KAGRA S240511i: Updated Sky localization
  9. LIGO/Virgo/KAGRA S240511i: Identification of a GW compact binary merger candidate
  10. LIGO/Virgo/KAGRA S240422ed: P200 observations of AT2024hit
  11. LIGO/Virgo/KAGRA S240422ed: Candidates from the latest GW-MMADS DECam Observations
  12. LIGO/Virgo/KAGRA S240507p: Updated Sky localization and EM Bright Classification
  13. LIGO/Virgo/KAGRA S240422ed: Upper limits from a two-week IceCube neutrino search
  14. LIGO/Virgo/KAGRA S240507p: Identification of a GW compact binary merger candidate
  15. LIGO/Virgo/KAGRA S240422ed: Additional WINTER near-infrared J-band observations
  16. LIGO/Virgo/KAGRA S240422ed: Swope Follow-up of AT2024hfr and AT2024hfs
  17. LIGO/Virgo/KAGRA S240505av: Updated Sky localization and EM Bright Classification
  18. LIGO/Virgo/KAGRA S240505av: Identification of a GW compact binary merger candidate
  19. GRB 240502C: Zeiss-1000 at Koshka observatory observations of GOTO optical counterpart candidates
  20. GW170817: VLA observations at ~5.5 yrs since merger
  21. GRB 240502C: GOTO possible optical counterpart candidates
  22. LIGO/Virgo/KAGRA S240501an: Updated Sky localization and EM Bright Classification
  23. LIGO/Virgo/KAGRA S240430ca: Updated Sky localization and EM Bright Classification
  24. LIGO/Virgo/KAGRA S240501an: Identification of a GW compact binary merger candidate
  25. LIGO/Virgo/KAGRA S240430ca: Updated Sky localization and EM Bright Classification
  26. LIGO/Virgo/KAGRA S240430ca: Identification of a GW compact binary merger candidate
  27. Additional DECam GW-MMADS Candidates from three nights of observations
  28. LIGO/Virgo/KAGRA S240426s: Updated Sky localization
  29. LIGO/Virgo/KAGRA S240422ed: SRG/eROSITA archival upper limit for EP240426a
  30. LIGO/Virgo/KAGRA S240426dl: Updated Sky localization
  31. LIGO/Virgo/KAGRA S240428dr: Updated Sky localization
  32. LIGO/Virgo/KAGRA S240422ed: GECKO/KMTNet ToO observations
  33. LIGO/Virgo/KAGRA S240429an: Retraction of GW compact binary merger candidate
  34. LIGO/Virgo/KAGRA S240428dr: Identification of a GW compact binary merger candidate
  35. LIGO/Virgo/KAGRA S240422ed: J-band non-detection of J-GEM24a
  36. LIGO/Virgo/KAGRA S240422ed: DDOTI Optical Upper Limit for J-GEM24a
  37. LIGO/Virgo/KAGRA S240422ed: Observations with 1.6m Mephisto
  38. LIGO/Virgo/KAGRA S240422ed: A transient discovered from Subaru/MOIRCS near-infrared observations by J-GEM Collaboration
  39. LIGO/Virgo S240422ed: Swift XRT observation of EP240426a
  40. LIGO/Virgo/KAGRA S240422ed: NOT optical observations of EP240426a
  41. LIGO/Virgo/KAGRA S240422ed: Swope Follow-up of AT2024hfq, AT2024hfr, AT2024hfs, and AT2024hfx
  42. LIGO/Virgo/KAGRA S240422ed: GRANDMA Optical Upper Limits for EP240426a
  43. LIGO/Virgo/KAGRA S240426dl: Identification of a GW compact binary merger candidate
  44. LIGO/Virgo/KAGRA S240422ed: BOOTES-4/MET Optical Upper Limits for EP240426a
  45. LIGO/Virgo/KAGRA S240422ed: Continued Magellan Observations
  46. EP240426a: GMG optical upper limit
  47. LIGO/Virgo/KAGRA S240422ed: EP-FXT detection of a candidate counterpart EP240426a
  48. LIGO/Virgo/KAGRA S240426s: Identification of a GW compact binary merger candidate
  49. LIGO/Virgo/KAGRA S240422ed: Magellan Follow-up Observations of Swift/XRT candidates
  50. LIGO/Virgo/KAGRA S240422ed: Zwicky Transient Facility contuinued observations of S240422ed and candidate analysis
  51. LIGO/Virgo/KAGRA S240422ed: GOTO counterpart search update and AT2024hfx, AT2024hgl observations
  52. S240422ed: BlackGEM/MeerLICHT transient detection AT2024hgl/MLTJ080628.10-250116.4
  53. LIGO/Virgo/KAGRA S240422ed: PRIME near-infrared observations
  54. S240422ed: MeerLICHT/BlackGEM photometry on AT2024hfx and archival ZTF detection
  55. LIGO/Virgo/KAGRA S240422ed: Second night Pan-STARRS observations of the skymap
  56. LIGO/Virgo/KAGRA S240422ed: Additional DECam GW-MMADS Candidates from the first two nights of observations
  57. LIGO/Virgo/KAGRA S240422ed: ANU 2.3m followup of candidate counterparts
  58. LIGO/Virgo/KAGRA S240422ed: Magellan Spectrum of GW-MMADS Candidate AT2024hdo Indicates a Type II SN
  59. LIGO/Virgo/KAGRA S240422ed: SRG/eROSITA archival upper limits for Swift/XRT candidates
  60. LIGO/Virgo/KAGRA S240422ed: Archival BlackGEM/MeerLICHT detections of AT 2024hdr & AT 2024hdq
  61. LIGO/Virgo/KAGRA S240413p: DESGW DECam Follow-Up
  62. LIGO/Virgo/KAGRA S240422ed: No significant counterpart candidates in HAWC observations
  63. LIGO/Virgo/KAGRA S240422ed: Vetting of DECam Candidates Using Real-Time Resources and SAGUARO Infrastructure
  64. LIGO/Virgo/KAGRA S240422ed: No significant candidates in GRANDMA/FRAM Observations
  65. IceCube-240424A - IceCube observation of a high-energy neutrino candidate track-like event
  66. LIGO/Virgo/KAGRA S240422ed: MOSFIRE spectroscopy of the DECam GW-MMADS candidate AT 2024hdn
  67. LIGO/Virgo/KAGRA S240422ed: ATCA follow-up of candidate counterparts
  68. LIGO/Virgo/KAGRA S240422ed: MOSFIRE imaging of the DECam GW-MMADS candidate AT 2024hdm
  69. LIGO/Virgo/KAGRA S240422ed: Early X-ray Upper Limits from EP-WXT for the LVK Sky Localization Region
  70. LIGO/Virgo/KAGRA S240422ed: J-band non-detection of Mag24a
  71. LIGO/Virgo/KAGRA S240422ed: Continued Imaging of Mag24a
  72. LIGO/Virgo/KAGRA S240422ed: DECam GW-MMADS Candidates
  73. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-WXT for the Three Potential Electromagnetic Counterparts Reported So Far
  74. LIGO/Virgo/KAGRA S240422ed: Magellan Detection of a Potential Electromagnetic Counterpart
  75. LIGO/Virgo/KAGRA S240422ed: SAGUARO upper limits from CSS
  76. LIGO/Virgo/KAGRA S240422ed: LAST optical observations
  77. LIGO/Virgo/KAGRA S240421ar: Updated Sky localization
  78. LIGO/Virgo/KAGRA S240422ed: no candidate counterparts from Pan-STARRS observations of the skymap
  79. LIGO/Virgo/KAGRA S240422ed: GOTO counterpart search
  80. LIGO/Virgo/KAGRA S240423br: Retraction of GW compact binary merger candidate
  81. LIGO/Virgo/KAGRA S240422ed: no candidate counterparts from ATLAS observations
  82. LIGO/Virgo S240422ed: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  83. LIGO/Virgo/KAGRA S240422ed: GW-MMADS DECam observations
  84. LIGO/Virgo/KAGRA S240422ed: Magellan Observations
  85. LIGO/Virgo/KAGRA S240422ed: Updated NED Galaxies in the Localization Volume
  86. LIGO/Virgo/KAGRA S240422ed: AstroSat CZTI non-detection and upper limits
  87. LIGO/Virgo/KAGRA S240422ed: Upper limits from Fermi-GBM Observations
  88. LIGO/Virgo/KAGRA S240422ed: Updated Sky localization and EM Bright Classification
  89. LIGO/Virgo/KAGRA S240421ar: Upper limits from Swift/BAT-GUANO
  90. LIGO/Virgo/KAGRA S240422ed: Coverage and upper limits from MAXI/GSC observations
  91. LIGO/Virgo/KAGRA S240422ed: Identification of a GW compact binary merger candidate
  92. LIGO/Virgo/Kagra S240422ed: NED Galaxies in the Localization Volume
  93. GRB 240414A: AMI-LA radio observations
  94. EP240420a: Xinglong decaying optical counterpart
  95. GRB 240421B: Swift detection of a burst
  96. EP240420a: Nanshan optical counterpart observations
  97. EP240420a: GWAC-F50A optical upper limit
  98. LIGO/Virgo/KAGRA S240421ar: Identification of a GW unmodeled transient candidate
  99. EP240420a: NOT optical counterpart candidate and potential host
  100. GRB240418A - Candidate afterglow from NIRES

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