Image of the Week

 

HIP 70674 orbital solution resulting from Gaia DR3 processing

 

Figure 1: HIP 70674 radial velocities folded according to the derived orbital period. It contains 18 double lined transits (green and red dots) and 1 single lined transit (black dot). The error bars are smaller than the symbols. The radial velocity curve showing predicted fit lines as published in this 2015 IoW is shown at the top left corner. The phase shift of ≈ 0.41 between the two figures is due to the difference of our derived orbital parameters compared to those from the SB9 catalogue.

 

In 2015, after one year of data acquisition by Gaia, we reported the case of HIP 70674, a well-known double lined spectroscopic binary (SB2), with visual magnitude V=7.99. The aim was to demonstrate the capability of the Coordination Unit 6 (CU6) Single Transit Analysis (STA) pipeline to measure radial velocities from double lined spectra as observed by the Radial Velocity Spectrometer (RVS). The composite spectra have lines with smaller relative depths compared to single lined ones but the radial velocities derived by Gaia are still of very good quality. In the 2015 IoW, the measured radial velocities were plotted according to the ephemerides from the literature (SB9: Pourbaix et al. 2004).

We are now approaching Gaia Data Release 3, which will contain the results of the Coordination Unit 4 (CU4) Non Single Star (NSS) pipeline for SB2 stars. Presented here are the CU4 NSS pipeline results for HIP 70674 as an example of this processing.

First, this star passed through the STA pipeline, which processed simultaneously all its spectra (per-source processing) to ensure that they are modeled using a composite synthetic spectrum based on the same pair of templates over all transits. The pipeline measured the broadening velocity(*) for every component as well as their epoch radial velocities. Figure 2 shows two examples of the fit of an observed spectrum of HIP 70674 by the best composite synthetic spectrum.

 

Figure 2: The fit by a composite (red) synthetic spectrum of HIP 70674 observed spectra. Top panel: transit 15672150943102525 CCD 1 (phase=0.998); bottom panel: transit 36212304701190693 CCD 3 (phase=0.309). The epoch observed spectra will be part of the future Gaia Data Release 4.

 

The radial velocities provided by the CU6 STA pipeline are then processed by the CU4 NSS pipeline, which is intended to determine the orbital solutions of the spectroscopic binaries. 

Due to the similarity of the two stars, in terms of brightness and of spectral types, it should be noted that the STA pipeline cannot easily identify on a given transit which of the two measured radial velocities shall be assigned to one or the other of the two components. The association of the radial velocities is then performed by a dedicated period searching and sorting algorithm implemented in the NSS pipeline.

Figure 3 shows the diagram of RV2 versus RV1 after they were sorted by the NSS pipeline. The two sets of velocities are, as expected from the theory, perfectly anti-correlated (correlation coefficient = -0.999). This reflects the quality of the measurements as well as the efficiency of the sorting that was carried out. 

Figure 3: The diagram RV2 versus RV1 after DU434 sorting. The two sets of velocities are perfectly anti-correlated (correlation coefficient = -0.999).

 

The final phase folded curve is plotted in Figure 1. The orbital elements are of high quality and in good agreement with the published ones:

 

Orbital element SB9 value Gaia value Difference in sigma units
Period [day] 4.007390 ± 0.000029 4.007255 ± 0.000017 -4.0
Eccentricity 0.0 (Fixed) 0.009 ± 0.002 4.5
K1 [km/s] 78.88 ± 0.27 79.28 ± 0.18 1.2
K2 [km/s] 80.38 ± 0.39 80.17 ± 0.19 -0.5
ω [°] 0.0 (Fixed) -30.3 ± 12.0 -2.5
T[d] in J2016.0 -0.5859 ± 0.1448 1.0509 ± 0.1333 8.3

 

Table 1: Orbital elements of HIP 70674, with ω the argument of periastron and Tp the time of periastron passage. The difference in sigma units for the Tp is essentially due to a difference in the definition of the models.

 

In about one year, Gaia Data Release 3 (Gaia DR3) will release thousands of orbital solutions for such SB2 stars. The present case was particularly favorable due to the brightness of the object. 

 

(*) The line broadening is modeled by a rotational profile even if it may be due to other phenomena beside the stellar rotation (e.g. macro turbulence).

 

Credits: ESA/Gaia/DPAC/CU4-CU6, Yassine Damerdji (CRAAG/IAGL), Eric Gosset (IAGL), Ronny Blomme (ROB), Thierry Morel (IAGL), Pasquale Panuzzo (CNRS/Observatoire de Paris/PSL), NSS & DU650 teams.

 

[Published: 27/04/2021]

Image of the Week Archive

2021

24/09: Astrometric microlensing effect in the Gaia16aye event

22/09: the power of the third dimension - the discovery of a gigantic cavity in space

16/09: An alternative Gaia sky chart

25/08: Gaia Photometric Science Alerts and Gravitational Wave Triggers

09/07: How Gaia unveils what stars are made of

23/06: Interviews with CU3

27/04: HIP 70674 Orbital solution resulting from Gaia DR3 processing

30/03: First transiting exoplanet by Gaia

26/03: Apophis' Yarkovsky acceleration improved through stellar occultation

26/02: Matching observations to sources for Gaia DR4

2020

22/12: QSO emission lines in low-resolution BP/RP spectra

03/12: Gaia Early Data Release 3

29/10: Gaia EDR3 passbands

15/10: Star clusters are only the tip of the iceberg

04/09: Discovery of a year long superoutburst in a white dwarf binary

12/08: First calibrated XP spectra

22/07: Gaia and the size of the Solar System

16/07: Testing CDM and geometry-driven Milky Way rotation Curve Models

30/06: Gaia's impact on Solar system science

14/05: Machine-learning techniques reveal hundreds of open clusters in Gaia data

20/03: The chemical trace of Galactic stellar populations as seen by Gaia

09/01: Discovery of a new star cluster: Price-Whelan1

08/01: Largest ever seen gaseous structure in our Galaxy

2019
20/12: The lost stars of the Hyades
06/12: Do we see a dark-matter like effect in globular clusters?
12/11: Hypervelocity star ejected from a supermassive black hole
17/09: Instrument Development Award
08/08: 30th anniversary of Hipparcos
17/07: Whitehead Eclipse Avoidance Manoeuvre
28/06: Following up on Gaia Solar System Objects
19/06: News from the Gaia Archive
29/05: Spectroscopic variability of emission lines stars with Gaia
24/05: Evidence of new magnetic transitions in late-type stars
03/05: Atmospheric dynamics of AGB stars revealed by Gaia
25/04: Geographic contributions to DPAC
22/04: omega Centauri's lost stars
18/04: 53rd ESLAB symposium "the Gaia universe"
18/02: A river of stars
2018
21/12: Sonification of Gaia data
18/12: Gaia captures a rare FU Ori outburst
12/12: Changes in the DPAC Executive
26/11:New Very Low Mass dwarfs in Gaia data
19/11: Hypervelocity White Dwarfs in Gaia data
15/11: Hunting evolved carbon stars with Gaia RP spectra
13/11: Gaia catches the movement of the tiny galaxies surrounding the Milky Way
06/11: Secrets of the "wild duck" cluster revealed
12/10: 25 years since the initial GAIA proposal
09/10: 3rd Gaia DPAC Consortium Meeting
30/09: A new panoramic sky map of the Milky Way's Stellar Streams
25/09: Plausible home stars for interstellar object 'Oumuamua
11/09: Impressions from the IAU General Assembly
30/06: Asteroids in Gaia Data
14/06: Mapping and visualising Gaia DR2

25/04: In-depth stories on Gaia DR2

14/04: Gaia tops one trillion observations
16/03: Gaia DR2 Passbands
27/02: Triton observation campaign
11/02: Gaia Women In Science
29/01: Following-up on Gaia
2017
19/12: 4th launch anniversary
24/11: Gaia-GOSA service
27/10: German Gaia stamp in the making
19/10: Hertzsprung-russell diagram using Gaia DR1
05/10: Updated prediction to the Triton occultation campaign
04/10: 1:1 Gaia model arrives at ESAC
31/08: Close stellar encounters from the first Gaia data release
16/08: Preliminary view of the Gaia sky in colour
07/07: Chariklo stellar occultation follow-up
24/04: Gaia reveals the composition of asteroids
20/04: Extra-galactic observations with Gaia
10/04: How faint are the faintest Gaia stars?
24/03: Pulsating stars to study Galactic structures
09/02: Known exoplanetary transits in Gaia data
31/01: Successful second DPAC Consortium Meeting
2016
23/12: Interactive and statistical visualisation of Gaia DR1 with vaex
16/12: Standard uncertainties for the photometric data (in GDR1)
25/11: Signature of the rotation of the galactic bar uncovered
15/11: Successful first DR1 Workshop
27/10: Microlensing Follow-Up
21/10: Asteroid Occultation
16/09: First DR1 results
14/09: Pluto Stellar Occultation
15/06: Happy Birthday, DPAC!
10/06: 1000th run of the Initial Data Treatment system
04/05: Complementing Gaia observations of the densest sky regions
22/04: A window to Gaia - the focal plane
05/04: Hipparcos interactive data access tool
24/03: Gaia spots a sunspot
29/02: Gaia sees exploding stars next door
11/02: A new heart for the Gaia Object Generator
04/02: Searching for solar siblings with Gaia
28/01: Globular cluster colour-magnitude diagrams
21/01: Gaia resolving power estimated with Pluto and Charon
12/01: 100th First-Look Weekly Report
06/01: Gaia intersects a Perseid meteoroid
2015
18/12: Tales of two clusters retold by Gaia
11/11: Lunar transit temperature plots
06/11: Gaia's sensors scan a lunar transit
03/11: Celebrity comet spotted among Gaia's stars
09/10: The SB2 stars as seen by Gaia's RVS
02/10: The colour of Gaia's eyes
24/09: Estimating distances from parallaxes
18/09: Gaia orbit reconstruction
31/07: Asteroids all around
17/07: Gaia satellite and amateur astronomers spot one in a billion star
03/07: Counting stars with Gaia
01/07: Avionics Model test bench arrives at ESOC
28/05: Short period/faint magnitude Cepheids in the Large Magellanic Cloud
19/05: Visualising Gaia Photometric Science Alerts
09/04: Gaia honours Einstein by observing his cross
02/04: 1 April - First Look Scientists play practical joke
05/03: RR Lyrae stars in the Large Magellanic Cloud as seen by Gaia
26/02: First Gaia BP/RP deblended spectra
19/02: 13 months of GBOT Gaia observations
12/02: Added Value Interface Portal for Gaia
04/02: Gaia's potential for the discovery of circumbinary planets
26/01: DIBs in three hot stars as seen by Gaia's RVS
15/01: The Tycho-Gaia Astrometric Solution
06/01: Close encounters of the stellar kind
2014
12/12: Gaia detects microlensing event
05/12: Cat's Eye Nebula as seen by Gaia
01/12: BFOSC observation of Gaia at L2
24/11: Gaia spectra of six stars
13/11: Omega Centauri as seen by Gaia
02/10: RVS Data Processing
12/09: Gaia discovers first supernova
04/08: Gaia flag arrives at ESAC
29/07: Gaia handover
15/07: Eclipsing binaries
03/07: Asteroids at the "photo finish"
19/06: Calibration image III - Messier 51
05/06: First Gaia BP/RP and RVS spectra
02/06: Sky coverage of Gaia during commissioning
03/04: Gaia source detection
21/02: Sky-background false detections in the sky mapper
14/02: Gaia calibration images II
06/02: Gaia calibration image I
28/01: Gaia telescope light path
17/01: First star shines for Gaia
14/01: Radiation Campaign #4
06/01: Asteroid detection by Gaia
2013
17/12: Gaia in the gantry
12/12: The sky in G magnitude
05/12: Pre-launch release of spectrophotometric standard stars
28/11: From one to one billion pixels
21/11: The Hipparcos all-sky map
15/10: Gaia Sunshield Deployment Test
08/10: Initial Gaia Source List
17/09: CU1 Operations Workshop
11/09: Apsis
26/08: Gaia arrival in French Guiana
20/08: Gaia cartoons
11/07: Model Soyuz Fregat video
01/07: Acoustic Testing
21/06: SOVT
03/06: CU4 meeting #15
04/04: DPCC (CNES) 
26/03: Gaia artist impression 
11/02: Gaia payload testing  
04/01: Space flyby with Gaia-like data
2012
10/12: DPAC OR#2. Testing with Planck
05/11: Galaxy detection with Gaia
09/10: Plot of part of the GUMS-10 catalogue
23/07: "Gaia" meets at Gaia
29/06: The Sky as seen by Gaia
31/05: Panorama of BAM clean room
29/03: GREAT school results
12/03: Scanning-law movie
21/02: Astrometric microlensing and Gaia
03/02: BAM with PMTS
12/01: FPA with all the CCDs and WFSs
2011
14/12: Deployable sunshield
10/11: Earth Trojan search
21/10: First Soyuz liftoff from the French Guiana
20/09: Fast 2D image reconstruction algorithm
05/09: RVS OMA
10/08: 3D distribution of the Gaia catalogue
13/07: Dynamical Attitude Model
22/06: Gaia's view of open clusters
27/05: Accuracy of the stellar transverse velocity
13/05: Vibration test of BAM mirrors
18/04: L. Lindegren, Dr. Honoris Causa of the Observatory of Paris
19/01: Detectability of stars close to Jupiter
05/01: Delivery of the WFS flight models
2010
21/12: The 100th member of CU3
17/11: Nano-JASMINE and AGIS
27/10: Eclipsing binary light curves fitted with DPAC code
13/10: Gaia broad band photometry
28/09: Measuring stellar parameters and interstellar extinction
14/09: M1 mirror
27/08: Quest for the Sun's siblings
 
Please note: Entries from the period 2003-2010 are available in this PDF document.