Image of the Week

 

Gaia Photometric Science Alerts and Gravitational Wave Triggers

 

The all-sky distribution of candidate transients detected during the year 2018 using the GaiaX algorithm (Kostrzewa-Rutkowska et al. 2020). The map resolution is HEALPix of nside 32. The plot is in Galactic coordinates.

 

Motivated by the recent developments in multi-messenger astronomy, and in particular the detection of an electro-magnetic counterpart to the gravitational wave (GW) event GW170817, and by the non-detections of subsequent GW events involving at least one neutron star, a contribution from Gaia to this emerging field has been discussed.

This Gaia contribution requires an improvement of the sensitivity of the Gaia Photometric Science Alerts stream, in two ways:

  1. Allowing for fainter alerts (the current limit of published alerts is: G=19).
  2. Allowing a single detection to trigger an alert (for normal alerts, two transits are required for the detection).

There are very good reasons for having these restrictions in routine operations – they minimise the false alarm rate. But this comes at the price of reduced completeness (Hodgkin et al. 2021), especially for fast and faint transients (such as kilonovae). When there is a coincidence with other surveys (be they electromagnetic, or gravitational wave), one can afford to be more relaxed, and take advantage of this coincidence in time and position.

LIGO/Virgo run number 4 is expected to start in about one year, and will include public releases of high signal-to-noise GW events. Gaia Photometric Science Alerts could then contribute to the search for the optical counterpart of any new GW event by publishing our extra (though less pure) alert stream (called GaiaX).

The Gaia team involved has been running tests behind-the-scenes, and has identified most of the causes of single-transit spurious detections, which could have a variety of causes, such as the detection of solar system objects or artefacts from bright stars. What is left now is a background rate of detections (about 50 per day) that is not fully understood. These may be caused by different artefacts of unknown nature, but it is expected that an important fraction of this background rate of detections may actually be real astrophysical events.

Ahead of turning on the GaiaX stream of alerts fully, an experiment will be performed. The Gaia on-sky field-of-view will be observed simultaneously with the MeerLICHT telescope. True astrophysical events should be common to both telescopes. During this initial phase the GaiaX detections will be published, in the hope that they could lead to exciting new science, or (at the very least) help to provide a detailed investigation of the GaiaX transient candidates.

The test phase of the new GaiaX alert stream will be available at this website from 1st September 2021, and will last for four weeks. The data are organized by IDT run number (Initial Data Treatment, operated at SOC, with an approximately daily processing cadence). The index page of the GaiaX alerts homepage lists the start and end times of the observations included in each run, and the number of alerts detected in the run. Also, the date of publication of the run is given, and for each run, a link to a CSV file containing the GaiaX alert candidates.

The CSV file contains the following data described here:

  • Name: Unique name of the alert. Please use this name when referring to the Gaia data of the alert in publications.
  • SourceId: Note: this is a preliminary ID coming from the initial data treatment and may be changed for the official Gaia Data Releases. It may help to confirm alerts coming from the same source observed multiple times by Gaia.
  • RA, Dec: ICRS, accurate to 50 milli-arcsec.
  • ObsTime: Time of observation of the event that triggered the alert, in TCB.
  • GMag: Gaia G-band magnitude, calibrated by the CU5 Photometric One Day Calibration (PODC, see Hodgkin et al. 2021 for details).
  • GMagErr: Observed variation of magnitude (standard deviation of measurements across the transit) of the alerting source, in Gaia's G band.

When using these data, please credit the work of the Gaia Data Processing and Analysis Consortium by adding an acknowledgement to your work as follows:

“This research or product makes use of public data provided by ESA/Gaia/DPAC/CU5”, and please include the following references in any publication: Kostrzewa-Rutkowska et al. 2020 (MNRAS, 493, 3264), and Hodgkin et al. 2021.

 

Access the GaiaX Alert Test stream (from 1 September for four weeks)

 

Credits: Zuzanna Kostrzewa-Rutkowska (Leiden University, SRON) Peter Jonker, Deepak Eappachen (SRON / Radboud University) Sumedha Biswas (Radboud University) Prof.dr. Paul Groot (Radboud University / University of Cape Town / SAAO) Abdullah Yoldas, Guy Rixon, Diana Harrison, Simon Hodgkin (Cambridge University)

Published: 25/08/2021

 

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.