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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').

22198 results found.

  1. EP240426b: AST3-2 optical upper limit
  2. LIGO/Virgo/KAGRA S240422ed: Observations with 1.6m Mephisto
  3. LIGO/Virgo S240422ed: Swift XRT observation of EP240426a
  4. LIGO/Virgo/KAGRA S240422ed: NOT optical observations of EP240426a
  5. EP240426b: EP-WXT detection of a new fast X-ray transient
  6. LIGO/Virgo/KAGRA S240422ed: Archival radio detection of EP240426a
  7. LIGO/Virgo/KAGRA S240422ed: Swope Follow-up of AT2024hfq, AT2024hfr, AT2024hfs, and AT2024hfx
  8. LIGO/Virgo/KAGRA S240422ed: BOOTES-6/DPRT optical upper limits for EP240426a
  9. LIGO/VIRGO/KAGRA S240422ed: Historical variability for EP240426a
  10. GRB 240426A: AstroSat CZTI detection
  11. XMM-Newton observation of EP240426a
  12. LIGO/Virgo/KAGRA S240426dl: Identification of a GW compact binary merger candidate
  13. GRB 240414A: NOEMA detection
  14. LIGO/Virgo/KAGRA S240422ed: EP240426a possible optical detection
  15. EP240426a: GMG optical upper limit
  16. LVK S240422ed: Further Swift-XRT followup of three sources
  17. LIGO/Virgo/KAGRA S240426s: Identification of a GW compact binary merger candidate
  18. IceCube-240424A: Upper limits from a search for additional neutrino events in IceCube
  19. LIGO/Virgo/KAGRA S240422ed: PRIME near-infrared observations
  20. LIGO/Virgo/KAGRA S240422ed: 2.5m PRL Telescope follow-up of the Swift/XRT source S240422ed_X190
  21. LIGO/Virgo/KAGRA S240422ed: Second night Pan-STARRS observations of the skymap
  22. LIGO/Virgo/KAGRA S240422ed: Further near-infrared observations with Subaru/MOIRCS by J-GEM Collaboration
  23. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-FXT for the Potential Electromagnetic Counterparts Reported by Swift and DECam
  24. LIGO/Virgo/KAGRA S240422ed: Upper limits from GECAM Observations
  25. LIGO/Virgo/KAGRA S240422ed: No significant candidates in GRANDMA and Kilonova-Catcher galaxy targeting observations
  26. LIGO/Virgo/KAGRA S240422ed: Additional DECam GW-MMADS Candidates from the first two nights of observations
  27. LIGO/Virgo/KAGRA S240422ed: SRG/eROSITA archival upper limits for Swift/XRT candidates
  28. GRB 240419B: Swift-BAT refined analysis
  29. GRB 240421B: Swift-BAT refined analysis
  30. GRB 240422A: Glowbug gamma-ray detection
  31. LIGO/Virgo/KAGRA S240422ed: Archival BlackGEM/MeerLICHT detections of AT 2024hdr & AT 2024hdq
  32. LIGO/Virgo/KAGRA S240422ed: Himalayan Chandra Telescope follow-up of the Swift/XRT source S240422ed_X101
  33. LIGO/Virgo/KAGRA S240422ed: No significant counterpart candidates in HAWC observations
  34. LIGO/Virgo/KAGRA S240422ed: No significant candidates in GRANDMA/FRAM Observations
  35. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-WXT for the Potential Electromagnetic Counterparts Reported by Swift and DECam
  36. LIGO/Virgo S240422ed: Swift-XRT detection of 3 possible counterparts
  37. LIGO/Virgo/KAGRA S240422ed: Early X-ray Upper Limits from EP-WXT for the LVK Sky Localization Region
  38. LIGO/Virgo/KAGRA S240422ed: J-band non-detection of Mag24a
  39. LIGO/Virgo/KAGRA S240422ed: Continued Imaging of Mag24a
  40. LIGO/Virgo/KAGRA S240422ed: Archival DECaPSs2 observations of the field of Mag24a
  41. LIGO/Virgo/KAGRA S240422ed: NOT J-band upper limit on the Swift/XRT source S240422ed_X61
  42. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-WXT for the Three Potential Electromagnetic Counterparts Reported So Far
  43. LIGO/Virgo/KAGRA S240422ed: Subaru/MOIRCS near-infrared observations by J-GEM Collaboration
  44. LIGO/Virgo/KAGRA S240422ed: WINTER J-band upper limits on the Swift/XRT source S240422ed_X61
  45. IceCube-240419A: Upper limits from a search for additional neutrino events in IceCube
  46. LIGO/Virgo/KAGRA S240421ar: Updated Sky localization
  47. LIGO/Virgo/KAGRA S240422ed: GW-MMADS DECam upper limits on the Swift/XRT source S240422ed_X61
  48. LIGO/Virgo/KAGRA S240422ed: no candidate counterparts from Pan-STARRS observations of the skymap
  49. LIGO/Virgo/KAGRA S240422ed: No Counterparts in DDOTI/OAN Optical Observations
  50. GRB 240419A: Swift-BAT refined analysis
  51. GRB 240418A: Swift-BAT refined analysis
  52. LXT240402A/GRB240402B: Chandra X-ray detection
  53. LIGO/Virgo/KAGRA S240422ed: no candidate counterparts from ATLAS observations
  54. LIGO/Virgo/KAGRA S240422ed: WINTER near-infrared J-band observations
  55. LIGO/Virgo S240422ed: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  56. LIGO/Virgo/KAGRA S240422ed: GW-MMADS DECam observations
  57. LIGO/Virgo/KAGRA S240422ed: Updated NED Galaxies in the Localization Volume
  58. LIGO/Virgo/KAGRA S240422ed: AstroSat CZTI non-detection and upper limits
  59. LIGO/Virgo/KAGRA S240422ed: Upper limits from Fermi-GBM Observations
  60. LIGO/Virgo/KAGRA S240422ed: Updated Sky localization and EM Bright Classification
  61. LIGO/Virgo/KAGRA S240421ar: Upper limits from Swift/BAT-GUANO
  62. LIGO/Virgo/KAGRA S240422ed: Coverage and upper limits from MAXI/GSC observations
  63. LIGO/Virgo/KAGRA S240422ed: Identification of a GW compact binary merger candidate
  64. LIGO/Virgo/Kagra S240422ed: NED Galaxies in the Localization Volume
  65. GRB 240421A: Glowbug gamma-ray detection
  66. GRB 240414A: radio detection with the VLA
  67. Fermi-LAT gamma-ray observations of IceCube-240419A
  68. GRB 240414A: AMI-LA radio observations
  69. GRB 240414A: LBT optical detection
  70. GRB 240419B : MITSuME Akeno optical upper limits
  71. GRB 240415B: Swift-XRT observations
  72. GRB 240415A: Swift-XRT refined Analysis
  73. GRB240421B: Zadko Observations
  74. GRB 240421B: Fermi GBM Observation
  75. GRB 240421B: Swift-XRT refined Analysis
  76. GRB240421B: BOOTES-5/JGT optical upper limit
  77. GRB 240421B: J-band upper limits from WINTER
  78. GRB 240421B: Swift/UVOT Upper Limits
  79. GRB 240421B: Enhanced Swift-XRT position
  80. EP240417a: no counterpart detection by SOAR
  81. EP240420a: Xinglong decaying optical counterpart
  82. GRB 240421B: Swift detection of a burst
  83. EP240420a: Nanshan optical counterpart observations
  84. EP240420a: GWAC-F50A optical upper limit
  85. LIGO/Virgo/KAGRA S240421ar: Identification of a GW unmodeled transient candidate
  86. EP240420a: detection of fading X-ray emission with refined position by EP-FXT
  87. EP240420a: NOT optical counterpart candidate and potential host
  88. GRB240419A: Skynet Optical Afterglow Analysis
  89. GRB240418A - Candidate afterglow from NIRES
  90. GRB 240419B: Swift/UVOT Upper Limits
  91. EP240420a: EP-WXT detection of a fast X-ray transient
  92. GRB 240419A: Swift/UVOT Upper Limits
  93. GRB 240419B: Swift-XRT refined Analysis
  94. GRB 240419B: optical afterglow from the NOT
  95. EP240414a: Near-IR observations with NIRES and WINTER
  96. GRB 240419B: Enhanced Swift-XRT position
  97. GRB 240418A: Swift/UVOT Upper Limits
  98. GRB 240419A: REM NIR afterglow detection
  99. GRB 240419A: Swift-XRT refined Analysis
  100. GRB 240418A: Swift-XRT refined Analysis

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